User:Tohline/vtk/SimpleCubeTutorial - Revision history

Tohline: /* Specifying Colors of Cell Faces via a User-defined Color Table */ Add footnotes regarding color-by-name conventions

2014-04-27T21:04:02Z

Specifying Colors of Cell Faces via a User-defined Color Table: Add footnotes regarding color-by-name conventions

← Older revision		Revision as of 21:04, 27 April 2014
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	</pre>		</pre>
	</td>		</td>
	<td align="~~center~~" rowspan="3">		<td align="left" rowspan="3">

	<table border="1" cellpadding="5" align="center">		<table border="1" cellpadding="5" align="center">
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	</tr>		</tr>
	</table>		</table>
	See also Figure 3-4 (p. 38) of <br><font size="-2">[http://www.amazon.com/Visualization-Toolkit-Object-Oriented-Approach-Graphics/dp/193093419X/ref=pd_sim_sbs_b_1?ie=UTF8&refRID=0EFGPTSBP5E136WEK4V7 Schroeder, Martin, & Lorensen (2006)]</font>		See also …
	&~~nbsp~~;		* Figure 3-4 (p. 38) of <br><font size="-2">[http://www.amazon.com/Visualization-Toolkit-Object-Oriented-Approach-Graphics/dp/193093419X/ref=pd_sim_sbs_b_1?ie=UTF8&refRID=0EFGPTSBP5E136WEK4V7 Schroeder, Martin, & Lorensen (2006)]</font>
	~~<br>~~		and details regarding the community's Color-by-Name conventions …
	~~ ~~		* [http://www.vtk.org/Wiki/VTK/Examples/Python/Visualization/VTKNamedColorPatches_html vtk's official website]
	~~<br>~~		* [http://www.w3.org/TR/css3-color/#svg-color w3 specification]
	~~ ~~		* [http://en.wikipedia.org/wiki/Web_colors Wikipedia discussion]
	~~<br>~~
	~~ ~~
	~~<br>~~
	~~ ~~
	~~<br>~~
	~~ ~~
	~~<br>~~

	<br>		<br>

Tohline: /* WarpScalar */ Explain different color interpolation for cell versus point data

2014-04-26T22:02:37Z

WarpScalar: Explain different color interpolation for cell versus point data

← Older revision		Revision as of 22:02, 26 April 2014
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	</table>		</table>
	</div>		</div>


			The following excerpt from §5.1 (specifically, p. 77) of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide''] explains why the two images shown on the right-hand side of the above figure have very different color patterns:
			<table border="0" cellpadding="8" align="center" width="80%">
			<tr><td align="left">
			"Another important feature of ''vtkMapper'' is controlling which attribute data (i.e., point or cell scalars, or a general data array) is used to color objects." "Note that [different methods within the ''vtkMapper'' module] give strikingly different results: point attribute data is interpolated across rendering primitives during the rendering process, whereas cell attribute data colors the cell a constant value."
			</td></tr>
			</table>

	=Other Example Input Files and VisTrails Pipelines=		=Other Example Input Files and VisTrails Pipelines=

Tohline: /* XML-Formatted Input */ Illustrate how to insert comment tags into XML-formatted input data files

2014-04-26T20:07:13Z

XML-Formatted Input: Illustrate how to insert comment tags into XML-formatted input data files

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	==XML-Formatted Input==		==XML-Formatted Input==
			===Overview===
	As is explained in §15.3 (see the bottom of p. 336) of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide,'' authored and published by Kitware, Inc.], VTK (and VisTrails) also supplies ''Readers'' that accept XML-formatted input data. An example XML-formatted data file is shown immediately following this paragraph; it also can be obtained at the following website:		As is explained in §15.3 (see the bottom of p. 336) of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide,'' authored and published by Kitware, Inc.], VTK (and VisTrails) also supplies ''Readers'' that accept XML-formatted input data. An example XML-formatted data file is shown immediately following this paragraph; it also can be obtained at the following website:
	<div align="center"> [http://www.phys.lsu.edu/~tohline/vistrails/datafiles/XMLformattedSimpleCube.vtp http://www.phys.lsu.edu/~tohline/vistrails/datafiles/XMLformattedSimpleCube.vtp]</div>		<div align="center"> [http://www.phys.lsu.edu/~tohline/vistrails/datafiles/XMLformattedSimpleCube.vtp http://www.phys.lsu.edu/~tohline/vistrails/datafiles/XMLformattedSimpleCube.vtp]</div>
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	<font color="blue">'''No Color Table:''' </font>		<font color="blue">'''No Color Table:''' </font>
	As far as I have been able to ascertain, XML-formatted data files cannot be used to define LOOKUP_TABLEs — that is, color tables. Hence, as illustrated in the "Pipeline02" figure shown here on the right, a ''vtkLookupTable'' module must be inserted into the VisTrails pipeline if the user wants to define the color table.		As far as I have been able to ascertain, XML-formatted data files cannot be used to define LOOKUP_TABLEs — that is, color tables. Hence, as illustrated in the "Pipeline02" figure shown here on the right, a ''vtkLookupTable'' module must be inserted into the VisTrails pipeline if the user wants to define the color table.

			===Comment Lines and Deleting XML Pieces===
			Two major advantages of XML-formatted input data files is the ability to segment the data — and rendered elements of a scene — into separate ''Pieces'' and, then, the ability to "comment out" one or more of these pieces when you want to simplify the scene. The following ASCII data file illustrates how the ''Simple Cube'' can be subdivided into a pair of 3-sided figures and how, by simply inserting or deleting a comment line, the two ''Pieces'' can be rendered together or separately.

			<div align="left">
			<pre>
			<?xml version="1.0"?>
			<VTKFile type="PolyData" version="0.1" byte_order="LittleEndian" compressor="vtkZLibDataCompressor">
			<PolyData>
			<!-- This is three of the sides of the cube -->
			<Piece NumberOfPoints="8" NumberOfPolys="3">
			<CellData Scalars="temperature" Normals="cell_normals">
			<DataArray type="Float32" Name="temperature" format="ascii">
			0.14286 0.28571 0.42857
			</DataArray>
			<DataArray type="Int32" Name="cell_normals" NumberOfComponents="3" format="ascii">
			0 0 1 0 0 1 0 -1 0
			</DataArray>
			</CellData>
			<Points>
			<DataArray type="Float32" NumberOfComponents="3" format="ascii">
			0 0 0 1 0 0
			1 1 0 0 1 0
			0 0 1 1 0 1
			1 1 1 0 1 1
			</DataArray>
			</Points>
			<Polys>
			<DataArray type="Int32" Name="connectivity" format="ascii">
			0 1 2 3 4 5 6 7 0 1 5 4
			</DataArray>
			<DataArray type="Int32" Name="offsets" format="ascii">
			4 8 12
			</DataArray>
			</Polys>
			</Piece>
			<!-- This is the other three sides of the cube
			<Piece NumberOfPoints="8" NumberOfPolys="3">
			<CellData Scalars="temperature" Normals="cell_normals">
			<DataArray type="Float32" Name="temperature" format="ascii">
			0.57143 0.71429 0.85714
			</DataArray>
			<DataArray type="Int32" Name="cell_normals" NumberOfComponents="3" format="ascii">
			0 1 0 -1 0 0 1 0 0
			</DataArray>
			</CellData>
			<Points>
			<DataArray type="Float32" NumberOfComponents="3" format="ascii">
			0 0 0 1 0 0
			1 1 0 0 1 0
			0 0 1 1 0 1
			1 1 1 0 1 1
			</DataArray>
			</Points>
			<Polys>
			<DataArray type="Int32" Name="connectivity" format="ascii">
			2 3 7 6 0 4 7 3 1 2 6 5
			</DataArray>
			<DataArray type="Int32" Name="offsets" format="ascii">
			4 8 12
			</DataArray>
			</Polys>
			</Piece>
			-->
			</PolyData>
			</VTKFile>
			</pre>
			</div>

			<font color="blue">'''General Explanation:''' </font>
			* The fourth line of the above ASCII data file is a single, standard XML-formatted comment line — see the explanation provided, for example, on the [http://en.wikipedia.org/wiki/XML#Comments Wikipedia page that explains XML comment tags]. By XML convention, it begins with the string "<math>~< !--</math>" and ends with the string "<math>~--></math>". The same beginning and ending strings also appear, respectively, as lines 31 and 58 in the data file. In the first case, because the two strings appear on the same line of the file, they simply serve to encapsulate a short comment. In the second case, all of the ASCII text that falls between lines 31 and 58 are considered part of the "comment" and therefore the second ''Piece'' of the cube is ignored by the ''XMLPolyDataReader''. As presented here, this input data file will generate only three sides of the cube. The entire cube will be rendered if line 58 is deleted and the string "<math>~--></math>" is added to the end of line 31.

	=WarpScalar=		=WarpScalar=

Tohline: /* Assigning NORMALS to POLYGONS */ Finish discussing Examples G and H.

2014-04-26T18:52:23Z

Assigning NORMALS to POLYGONS: Finish discussing Examples G and H.

← Older revision		Revision as of 18:52, 26 April 2014
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	* This is the set of six triplet values that should be entered into the above table to answer the tutorial quiz question: ''In what default direction will VTK determine that the normal to each of the cube's other five POLYGONS points?'' It differs from the set of cell_normals that we have explicitly inserted into Example F, above, in one very important way: The cell normal that has been assigned to POLYGON "0" in Example F is <math>~(x,y,z) = (0,0,-1)</math> whereas, given the order in which the POINTS are specified when POLYGON "0" is defined in the input data file (<font face="Courier">4 0 1 2 3</font>) and an adherence to the [http://en.wikipedia.org/wiki/Right-hand_rule right-hand rule], the default direction that would be assigned by VTK is <math>~(x,y,z) = (0,0,+1)</math>.		* This is the set of six triplet values that should be entered into the above table to answer the tutorial quiz question: ''In what default direction will VTK determine that the normal to each of the cube's other five POLYGONS points?'' It differs from the set of cell_normals that we have explicitly inserted into Example F, above, in one very important way: The cell normal that has been assigned to POLYGON "0" in Example F is <math>~(x,y,z) = (0,0,-1)</math> whereas, given the order in which the POINTS are specified when POLYGON "0" is defined in the input data file (<font face="Courier">4 0 1 2 3</font>) and an adherence to the [http://en.wikipedia.org/wiki/Right-hand_rule right-hand rule], the default direction that would be assigned by VTK is <math>~(x,y,z) = (0,0,+1)</math>.

	<font color="red">'''Comment#3 (by J. E. Tohline):'''</font> Initially, it wasn't obvious to me why POLYGON "0" was black. In my opinion, this was an odd ~~set of~~ set of numbers for the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide''] to provide ~~as part of~~ the simple "Cube example." choice to make if its purpose was to help students understand how the VTK and/or VisTrails machinery works. I, for one, was pretty sure I was still doing something wrong when I was finally able to read the "cube example" file into the VisTrails "vtkPolyDataReader," because most of the faces of the cube were painted the same color (blue) whereas I was expecting them all to have different, illustrative colors.		<font color="red">'''Comment#3 (by J. E. Tohline):'''</font> Initially, it wasn't obvious to me why POLYGON "0" was black. Because all of the "cell_normals" NORMALS that are explicitly specified in the Example F input data file point "out," I expected all six faces of the cube to be colored as shown in Example E. It took me a while to deduce that the default normal that VTK assigned to POLYGON "0" was <math>~(0,0,+1)</math> and pointed "into," rather than "out of," the cube. POLYGON "0" was painted black because the explicitly specified NORMAL in Example F pointed in the opposite direction to this default normal. In my opinion, this was an odd set of numbers for the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide''] to provide in order to illustrate how to specify NORMALS in the simple "Cube example."

			<font color="blue">Example G:</font>
			* If I was correct in explaining why POLYGON "0" was rendered black in Example F, then it should be possible to return POLYGON "0" to a red color by doing one of two things: (1) Flip the explicitly specified NORMAL to <math>~(0,0,+1)</math>, putting it in alignment with the normal's default specification; or (2) redefine POLYGON "0" by reversing the order in which its four POINTS are connected so that, according to the right-hand rule convention, the default normal would point "out of" rather than "into" the cube. The first of these two adjustments was made in Example G. Only one line of data in the Example G input file is different from the Example F input file: the NORMAL specified for POLYGON "0" is <math>~(0,0,1)</math> instead of <math>~(0,0,-1)</math>. As predicted, the VisTrails pipeline colored POLYGON "0" red instead of black.

	~~The six assigned floating-point numbers range~~ from ~~0.0 to 1.0,~~ in ~~increments~~ of ~~0.2. Presumably, VTK~~'~~s default color table spreads~~ the ~~rainbow of (RGB) colors across this same interval, with 0.0 being assigned to red and 1.0 being assigned to blue. It~~ is ~~therefore not surprising~~ that the ~~three initially visible faces~~ of the rendered ~~cube are~~ red, ~~green, and blue. The colors of~~ the other ~~three~~ faces ~~of the cube~~ are ~~revealed by using~~ the ~~computer mouse to spin~~ the ~~VisTrails spreadsheet rendering of the cube~~.		<font color="blue">Example H:</font>
			* Example H differs from Example F in that the direction of ''all six'' of the specified normals is reversed; that is, in Example H, all of the explicitly specified normals point "into" rather than "out of" the cube. As expected, the resulting rendered image has one red side (POLYGON "0"), while the other five cell faces are black — indicating that, for each face, the explicitly specified NORMAL and the default normal point in opposite directions.

	==XML-Formatted Input==		==XML-Formatted Input==

Tohline: /* Assigning NORMALS to POLYGONS */Change numbering of internal comment

2014-04-25T00:44:35Z

Assigning NORMALS to POLYGONS: Change numbering of internal comment

← Older revision		Revision as of 00:44, 25 April 2014
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	* This is the set of six triplet values that should be entered into the above table to answer the tutorial quiz question: ''In what default direction will VTK determine that the normal to each of the cube's other five POLYGONS points?'' It differs from the set of cell_normals that we have explicitly inserted into Example F, above, in one very important way: The cell normal that has been assigned to POLYGON "0" in Example F is <math>~(x,y,z) = (0,0,-1)</math> whereas, given the order in which the POINTS are specified when POLYGON "0" is defined in the input data file (<font face="Courier">4 0 1 2 3</font>) and an adherence to the [http://en.wikipedia.org/wiki/Right-hand_rule right-hand rule], the default direction that would be assigned by VTK is <math>~(x,y,z) = (0,0,+1)</math>.		* This is the set of six triplet values that should be entered into the above table to answer the tutorial quiz question: ''In what default direction will VTK determine that the normal to each of the cube's other five POLYGONS points?'' It differs from the set of cell_normals that we have explicitly inserted into Example F, above, in one very important way: The cell normal that has been assigned to POLYGON "0" in Example F is <math>~(x,y,z) = (0,0,-1)</math> whereas, given the order in which the POINTS are specified when POLYGON "0" is defined in the input data file (<font face="Courier">4 0 1 2 3</font>) and an adherence to the [http://en.wikipedia.org/wiki/Right-hand_rule right-hand rule], the default direction that would be assigned by VTK is <math>~(x,y,z) = (0,0,+1)</math>.

	<font color="red">'''Comment#4 (by J. E. Tohline):'''</font> Initially, it wasn't obvious to me why POLYGON "0" was black. In my opinion, this was an odd set of set of numbers for the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide''] to provide as part of the simple "Cube example." choice to make if its purpose was to help students understand how the VTK and/or VisTrails machinery works. I, for one, was pretty sure I was still doing something wrong when I was finally able to read the "cube example" file into the VisTrails "vtkPolyDataReader," because most of the faces of the cube were painted the same color (blue) whereas I was expecting them all to have different, illustrative colors.		<font color="red">'''Comment#3 (by J. E. Tohline):'''</font> Initially, it wasn't obvious to me why POLYGON "0" was black. In my opinion, this was an odd set of set of numbers for the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide''] to provide as part of the simple "Cube example." choice to make if its purpose was to help students understand how the VTK and/or VisTrails machinery works. I, for one, was pretty sure I was still doing something wrong when I was finally able to read the "cube example" file into the VisTrails "vtkPolyDataReader," because most of the faces of the cube were painted the same color (blue) whereas I was expecting them all to have different, illustrative colors.

Tohline: /* Constructing a More Sophisticated Cube */ Dress up the text and build better internal references

2014-04-25T00:42:35Z

Constructing a More Sophisticated Cube: Dress up the text and build better internal references

← Older revision		Revision as of 00:42, 25 April 2014
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	* "CELL_DATA 6" means that the subsequent numerical values should be assigned, in sequence, to each of the 6 polygonal (square) faces of the cube.		* "CELL_DATA 6" means that the subsequent numerical values should be assigned, in sequence, to each of the 6 polygonal (square) faces of the cube.
	* "SCALARS cell_scalars float 1" (see Examples A & B) means that, in each case, the assigned numerical value will be a floating-point number; "SCALARS cell_scalars int 1" (see Example C) means that the assigned numerical value will be an integer number. As necessary, the name "cell_scalars" will be used to reference this assigned set of scalar values. In principle, up to four separate sets of scalar values can be assigned to the faces of the cube (see the discussion associated with the parameter ''numComp'' on p. 329 of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide'']); the "1" at the end of this line of text indicates that the values associated with the name "cell_scalars" will be referenced as the ''first'' scalar component; it is optional if there is only one scalar component.		* "SCALARS cell_scalars float 1" (see Examples A & B) means that, in each case, the assigned numerical value will be a floating-point number; "SCALARS cell_scalars int 1" (see Example C) means that the assigned numerical value will be an integer number. As necessary, the name "cell_scalars" will be used to reference this assigned set of scalar values. In principle, up to four separate sets of scalar values can be assigned to the faces of the cube (see the discussion associated with the parameter ''numComp'' on p. 329 of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide'']); the "1" at the end of this line of text indicates that the values associated with the name "cell_scalars" will be referenced as the ''first'' scalar component; it is optional if there is only one scalar component.
	* "LOOKUP_TABLE default" means that the color that is assigned to each face will be determined by correlating the scalar value assigned to each face with the scalar values assigned to the standard rainbow of colors as defined by VTK's ''default'' lookup color table. ~~(See related <font color="red">Comment#1</font>, below.)~~		* "LOOKUP_TABLE default" means that the color that is assigned to each face will be determined by correlating the scalar value assigned to each face with the scalar values assigned to the standard rainbow of colors as defined by [[User:Tohline/vtk/SimpleCubeTutorial#Deciphering_VTK.27s_default_Lookup_Table\|VTK's ''default'' lookup color table]].

	<font color="blue">Example A:</font>		<font color="blue">Example A:</font>
	* The six assigned floating-point numbers range from 0.0 to 1.0, in increments of 0.2. ~~Presumably~~, VTK's default color table spreads the rainbow of (RGB) colors across this same interval, with 0.0 being assigned to red and 1.0 being assigned to blue. It is therefore not surprising that the three initially visible faces of the rendered cube are red, green, and blue. The colors of the other three faces of the cube are revealed by using the computer mouse to spin the VisTrails spreadsheet rendering of the cube.		* The six assigned floating-point numbers range from 0.0 to 1.0, in increments of 0.2. By inspection, it appears as though [[User:Tohline/vtk/SimpleCubeTutorial#Deciphering_VTK.27s_default_Lookup_Table\|VTK's default color table]] spreads the rainbow of (RGB) colors across this same interval, with 0.0 being assigned to red and 1.0 being assigned to blue. It is therefore not surprising that the three initially visible faces of the rendered cube are red, green, and blue. The colors of the other three faces of the cube are revealed by using the computer mouse to spin the VisTrails spreadsheet rendering of the cube.

	<font color="blue">Example B:</font>		<font color="blue">Example B:</font>
Line 283:		Line 283:

	<font color="blue">Example C:</font>		<font color="blue">Example C:</font>
	* The six assigned integer numbers range from 0 to 5, in increments of 1. One face — the one whose assigned scalar value is zero — is colored red; all five other faces are colored blue because the color table does not extend beyond 1.0 and VTK's default coloring rule is to peg scalar values at one (i.e., blue) if their assigned values are greater than unity.		* The six assigned integer numbers range from 0 to 5, in increments of 1. One face — the one whose assigned scalar value is zero — is colored red; all five other faces are colored blue because the color table does not extend beyond 1.0 and VTK's default coloring rule (see [[User:Tohline/vtk/SimpleCubeTutorial#mapping\|further elaboration, below]]) is to peg scalar values at one (i.e., blue) if their assigned values are greater than unity.

	<font color="red">'''Comment#1 (by J. E. Tohline):'''</font> Notice that, once a set of scalar values has been assigned to cell faces, the colors provided by the default LOOKUP_TABLE override the "tomato" color that is specified by the "vtkProperty" module of the VisTrails pipeline. The default "tomato" color can be retrieved without modifying the new input datafile by clicking on (i.e., selecting) the "vtkPolyDataMapper" module in the VisTrails pipeline, dragging the "ScalarVisibilityOff" method into the "Set Methods" segment of the VisTrials Builder Window, then reexecuting the pipeline.		<font color="red">'''Comment#1 (by J. E. Tohline):'''</font> Notice that, once a set of scalar values has been assigned to cell faces, the colors provided by the default LOOKUP_TABLE override the "tomato" color that is specified by the "vtkProperty" module of the VisTrails pipeline. The default "tomato" color can be retrieved without modifying the new input datafile by clicking on (i.e., selecting) the "vtkPolyDataMapper" module in the VisTrails pipeline, dragging the "ScalarVisibilityOff" method into the "Set Methods" segment of the VisTrials Builder Window, then reexecuting the pipeline.
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	====Deciphering VTK's ''default'' Lookup Table====		====Deciphering VTK's ''default'' Lookup Table====
	While color values that are prescribed by VTK's ''default'' lookup table have been used in the three example ASCII files just discussed — Examples A, B, and C — the ~~color~~ values ~~have~~ not been explicitly provided. When I began trying to understand, for myself, how color specification is handled in VTK, I was unable to locate a reference that spells out what the properties are of the ''default'' lookup table. By experimentation I discovered that a simple lookup table that comes close to mimicking the default one is as follows:		While color values that are prescribed by VTK's ''default'' lookup table have been used in the three example ASCII files just discussed — Examples A, B, and C — the code that VTK uses to map scalar values to specific colors has not been explicitly provided. When I began trying to understand, for myself, how color specification is handled in VTK, I was unable to locate a reference that spells out what the properties are of the ''default'' lookup table. By experimentation I discovered that a simple lookup table that comes close to mimicking the default one is as follows:
	<div align="center">		<div align="center">
	<pre>		<pre>
Line 303:		Line 303:
	</div>		</div>

	Eventually I discovered documentation that defines the default settings for VTK's color maps. In §6.6 of [http://www.amazon.com/Visualization-Toolkit-Object-Oriented-Approach-Graphics/dp/193093419X/ref=pd_sim_sbs_b_1?ie=UTF8&refRID=0EFGPTSBP5E136WEK4V7 Schroeder, Martin, & Lorensen (2006)] (see specifically the subsection titled '''Color Maps''' on p. 196), we are told the default settings are established via a specification of HSV (Hue-Saturation-Value) rather than via an <font face="Courier">rgb</font> specification. The default settings are: HueRange (0, 2/3); SaturationRange (1,1); and ValueRange (1,1).		Eventually I discovered documentation that defines the default settings for VTK's color maps. In §6.6 of [http://www.amazon.com/Visualization-Toolkit-Object-Oriented-Approach-Graphics/dp/193093419X/ref=pd_sim_sbs_b_1?ie=UTF8&refRID=0EFGPTSBP5E136WEK4V7 Schroeder, Martin, & Lorensen (2006)] (see specifically the subsection titled '''Color Maps''' on p. 196), we are told the default settings are established via a specification of HSV (Hue-Saturation-Value) rather than via an <font face="Courier">rgb</font> specification. The default settings are: HueRange (0, 2/3); SaturationRange (1,1); and ValueRange (1,1). This terminology is explained in an [[User:Tohline/vtk/ColorLookupTablea#Color_Lookup_Tables\|accompanying presentation]].

	===Specifying Colors of Cell Faces via a User-defined Color Table===		===Specifying Colors of Cell Faces via a User-defined Color Table===
	Now, suppose you don't like the colors that are assigned to each of the six faces of the cube by VTK's ''default'' color table. You can assign a different set of colors by explicitly defining your own "LOOKUP_TABLE." To illustrate how this is done, we have added nine additional lines of ASCII text to the input data files shown in ''Example D'' and ''Example E'', below. In both cases, we have inserted the LOOKUP_TABLE that has been provided as part of the "simple cube" example that is provided on pp. 331-332 of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide''].		Now, suppose you don't like the colors that are assigned to each of the six faces of the cube by [[User:Tohline/vtk/SimpleCubeTutorial#Deciphering_VTK.27s_default_Lookup_Table\|VTK's ''default'' color table]]. You can assign a different set of colors by explicitly defining your own "LOOKUP_TABLE." To illustrate how this is done, we have added nine additional lines of ASCII text to the input data files shown in ''Example D'' and ''Example E'', below. In both cases, we have inserted the LOOKUP_TABLE that has been provided as part of the "simple cube" example that is provided on pp. 331-332 of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide''].

	<div align="center">		<div align="center">
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	</div>		</div>
	* Notice that the LOOKUP_TABLE that has been added to the ASCII input data file in Examples D and E has ''tableName = my_table'' and has ''size = 8'', that is, it contains eight distinct <font face="Courier''>rgba</font> colors — each row of numbers specifies a distinct color and, in this case, they all have the same transparency, <math>~\alpha=1.0</math> (''i.e.,'' completely opaque). The "color code" table that has been provided to the right of Example E shows what color results from each of the eight assigned RGB triplets; the equivalent hexadecimal representation is provided for each color as well.		* Notice that the LOOKUP_TABLE that has been added to the ASCII input data file in Examples D and E has ''tableName = my_table'' and has ''size = 8'', that is, it contains eight distinct <font face="Courier''>rgba</font> colors — each row of numbers specifies a distinct color and, in this case, they all have the same transparency, <math>~\alpha=1.0</math> (''i.e.,'' completely opaque). The "color code" table that has been provided to the right of Example E shows what color results from each of the eight assigned RGB triplets; the equivalent hexadecimal representation is provided for each color as well.
	* As is explained in §6.2 of [http://www.amazon.com/Visualization-Toolkit-Object-Oriented-Approach-Graphics/dp/193093419X/ref=pd_sim_sbs_b_1?ie=UTF8&refRID=0EFGPTSBP5E136WEK4V7 Schroeder, Martin, & Lorensen (2006)], the mapping of scalar values to the color table proceeds as follows:		* <span id="mapping">As is explained</span> in §6.2 of [http://www.amazon.com/Visualization-Toolkit-Object-Oriented-Approach-Graphics/dp/193093419X/ref=pd_sim_sbs_b_1?ie=UTF8&refRID=0EFGPTSBP5E136WEK4V7 Schroeder, Martin, & Lorensen (2006)], the mapping of scalar values to the color table proceeds as follows:
	<div align="center">		<div align="center">
	<table border="1" cellpadding="5" width="75%">		<table border="1" cellpadding="5" width="75%">

Tohline: /* Constructing a More Sophisticated Cube */ Introduce a couple of new subsections discussing default color tables

2014-04-25T00:16:05Z

Constructing a More Sophisticated Cube: Introduce a couple of new subsections discussing default color tables

← Older revision		Revision as of 00:16, 25 April 2014
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	Now comes the fun part. Let's add some more information to the input model data file and, in addition, activate some more methods associated with the various VisTrails modules in order to generate more sophisticated cubes.		Now comes the fun part. Let's add some more information to the input model data file and, in addition, activate some more methods associated with the various VisTrails modules in order to generate more sophisticated cubes.

	===Specifying Colors of Cell Faces Using a Default Color Table===		===Default Color Table===

			====Specifying Colors of Cell Faces Using a Default Color Table====
	Tutorial Task: Assign a separate scalar value to each of the six faces of the cube, then color the faces differently, in accordance with their assigned scalar values. Continuing to adhere to the ''Simple Legacy Format'', this can be accomplished by adding nine lines of ASCII text to the text file that was created, above, to draw a minimalistic cube. Each column of the following table presents (top of the column) an example of this additional ASCII text, along with (bottom of the column) the resulting cube image, as rendered by VisTrails.		Tutorial Task: Assign a separate scalar value to each of the six faces of the cube, then color the faces differently, in accordance with their assigned scalar values. Continuing to adhere to the ''Simple Legacy Format'', this can be accomplished by adding nine lines of ASCII text to the text file that was created, above, to draw a minimalistic cube. Each column of the following table presents (top of the column) an example of this additional ASCII text, along with (bottom of the column) the resulting cube image, as rendered by VisTrails.
	<div align="center">		<div align="center">
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	<font color="red">'''Comment#2 (by J. E. Tohline):'''</font> Example C, shown here, adopts the same CELL_DATA scalar values that appear in the simple "cube example" presented in §15.3 (see the top of p. 332) of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide'']. In my opinion, this was a very odd choice to make if its purpose was to help students understand how the VTK and/or VisTrails machinery works. I, for one, was pretty sure I was still doing something wrong when I was finally able to read the "cube example" file into the VisTrails "vtkPolyDataReader," because most of the faces of the cube were painted the same color (blue) whereas I was expecting them all to have different, illustrative colors.		<font color="red">'''Comment#2 (by J. E. Tohline):'''</font> Example C, shown here, adopts the same CELL_DATA scalar values that appear in the simple "cube example" presented in §15.3 (see the top of p. 332) of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide'']. In my opinion, this was a very odd choice to make if its purpose was to help students understand how the VTK and/or VisTrails machinery works. I, for one, was pretty sure I was still doing something wrong when I was finally able to read the "cube example" file into the VisTrails "vtkPolyDataReader," because most of the faces of the cube were painted the same color (blue) whereas I was expecting them all to have different, illustrative colors.

			====Deciphering VTK's ''default'' Lookup Table====
	~~<div align="center" id="DefaultColorTable">~~		While color values that are prescribed by VTK's ''default'' lookup table have been used in the three example ASCII files just discussed — Examples A, B, and C — the color values have not been explicitly provided. When I began trying to understand, for myself, how color specification is handled in VTK, I was unable to locate a reference that spells out what the properties are of the ''default'' lookup table. By experimentation I discovered that a simple lookup table that comes close to mimicking the default one is as follows:
	~~<table border~~=~~"1" cellpadding~~=~~"8" width~~=~~"85%">~~
	~~<tr>~~
	~~<th align~~=~~"center">~~
	VTK's ~~Default Color~~ Lookup Table
	~~</th>~~
	~~</tr>~~
	~~<tr><td align~~=~~"left">~~
	~~<font~~ color~~="red">'''Comment#1 (by J. E. Tohline):'''</font> Color~~ values that are prescribed by VTK's ''default'' lookup table ~~are not explicitly provided~~ in the three example ASCII files ~~shown here~~. ~~Indeed~~, ~~to date~~ I ~~have been~~ unable to locate a reference that spells out what the properties are of the ''default'' lookup table. ~~But other, user-defined color lookup tables are prescribed and discussed, below. For the record, by~~ experimentation I ~~have~~ discovered that a simple lookup table that comes close to mimicking the default one is as follows:
	<div align="center">		<div align="center">
	<pre>		<pre>
Line 308:		Line 302:
	</pre>		</pre>
	</div>		</div>
	~~<div align="center">~~
	~~<table border="0" width="90%">~~		Eventually I discovered documentation that defines the default settings for VTK's color maps. In §6.6 of [http://www.amazon.com/Visualization-Toolkit-Object-Oriented-Approach-Graphics/dp/193093419X/ref=pd_sim_sbs_b_1?ie=UTF8&refRID=0EFGPTSBP5E136WEK4V7 Schroeder, Martin, & Lorensen (2006)] (see specifically the subsection titled '''Color Maps''' on p. 196), we are told the default settings are established via a specification of HSV (Hue-Saturation-Value) rather than via an <font face="Courier">rgb</font> specification. The default settings are: HueRange (0, 2/3); SaturationRange (1,1); and ValueRange (1,1).
	~~<tr><td align="left">~~
	~~<font color="lightgreen">'''Update on Comment#1 (by J. E. Tohline):'''</font>~~ I ~~have~~ discovered documentation that defines the default settings for VTK's color maps. In §6.6 of [http://www.amazon.com/Visualization-Toolkit-Object-Oriented-Approach-Graphics/dp/193093419X/ref=pd_sim_sbs_b_1?ie=UTF8&refRID=0EFGPTSBP5E136WEK4V7 Schroeder, Martin, & Lorensen (2006)] (see specifically the subsection titled '''Color Maps''' on p. 196), we are told the default settings are established via a specification of HSV (Hue-Saturation-Value) rather than via an <font face="Courier">rgb</font> specification. The default settings are: HueRange (0, 2/3); SaturationRange (1,1); and ValueRange (1,1).
	~~</td></tr>~~
	~~</table>~~
	~~</div>~~
	~~</td></tr>~~
	~~</table>~~
	~~</div>~~

	===Specifying Colors of Cell Faces via a User-defined Color Table===		===Specifying Colors of Cell Faces via a User-defined Color Table===
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	The six assigned floating-point numbers range from 0.0 to 1.0, in increments of 0.2. Presumably, VTK's default color table spreads the rainbow of (RGB) colors across this same interval, with 0.0 being assigned to red and 1.0 being assigned to blue. It is therefore not surprising that the three initially visible faces of the rendered cube are red, green, and blue. The colors of the other three faces of the cube are revealed by using the computer mouse to spin the VisTrails spreadsheet rendering of the cube.		The six assigned floating-point numbers range from 0.0 to 1.0, in increments of 0.2. Presumably, VTK's default color table spreads the rainbow of (RGB) colors across this same interval, with 0.0 being assigned to red and 1.0 being assigned to blue. It is therefore not surprising that the three initially visible faces of the rendered cube are red, green, and blue. The colors of the other three faces of the cube are revealed by using the computer mouse to spin the VisTrails spreadsheet rendering of the cube.


	==XML-Formatted Input==		==XML-Formatted Input==

Tohline: /* Specifying Colors of Cell Faces Using a Default Color Table */ Put more emphasis on segment pointing to VTK's default color lookup table

2014-04-24T23:54:07Z

Specifying Colors of Cell Faces Using a Default Color Table: Put more emphasis on segment pointing to VTK's default color lookup table

← Older revision		Revision as of 23:54, 24 April 2014
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	* The six assigned integer numbers range from 0 to 5, in increments of 1. One face — the one whose assigned scalar value is zero — is colored red; all five other faces are colored blue because the color table does not extend beyond 1.0 and VTK's default coloring rule is to peg scalar values at one (i.e., blue) if their assigned values are greater than unity.		* The six assigned integer numbers range from 0 to 5, in increments of 1. One face — the one whose assigned scalar value is zero — is colored red; all five other faces are colored blue because the color table does not extend beyond 1.0 and VTK's default coloring rule is to peg scalar values at one (i.e., blue) if their assigned values are greater than unity.

			<font color="red">'''Comment#1 (by J. E. Tohline):'''</font> Notice that, once a set of scalar values has been assigned to cell faces, the colors provided by the default LOOKUP_TABLE override the "tomato" color that is specified by the "vtkProperty" module of the VisTrails pipeline. The default "tomato" color can be retrieved without modifying the new input datafile by clicking on (i.e., selecting) the "vtkPolyDataMapper" module in the VisTrails pipeline, dragging the "ScalarVisibilityOff" method into the "Set Methods" segment of the VisTrials Builder Window, then reexecuting the pipeline.

			<font color="red">'''Comment#2 (by J. E. Tohline):'''</font> Example C, shown here, adopts the same CELL_DATA scalar values that appear in the simple "cube example" presented in §15.3 (see the top of p. 332) of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide'']. In my opinion, this was a very odd choice to make if its purpose was to help students understand how the VTK and/or VisTrails machinery works. I, for one, was pretty sure I was still doing something wrong when I was finally able to read the "cube example" file into the VisTrails "vtkPolyDataReader," because most of the faces of the cube were painted the same color (blue) whereas I was expecting them all to have different, illustrative colors.


			<div align="center" id="DefaultColorTable">
			<table border="1" cellpadding="8" width="85%">
			<tr>
			<th align="center">
			VTK's Default Color Lookup Table
			</th>
			</tr>
			<tr><td align="left">
	<font color="red">'''Comment#1 (by J. E. Tohline):'''</font> Color values that are prescribed by VTK's ''default'' lookup table are not explicitly provided in the three example ASCII files shown here. Indeed, to date I have been unable to locate a reference that spells out what the properties are of the ''default'' lookup table. But other, user-defined color lookup tables are prescribed and discussed, below. For the record, by experimentation I have discovered that a simple lookup table that comes close to mimicking the default one is as follows:		<font color="red">'''Comment#1 (by J. E. Tohline):'''</font> Color values that are prescribed by VTK's ''default'' lookup table are not explicitly provided in the three example ASCII files shown here. Indeed, to date I have been unable to locate a reference that spells out what the properties are of the ''default'' lookup table. But other, user-defined color lookup tables are prescribed and discussed, below. For the record, by experimentation I have discovered that a simple lookup table that comes close to mimicking the default one is as follows:
	<div align="center">		<div align="center">
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	</table>		</table>
	</div>		</div>
			</td></tr>
	<~~font color="red"~~>~~'''Comment#2 (by J. E. Tohline):'''~~</~~font~~> Notice that, once a set of scalar values has been assigned to cell faces, the colors provided by the default LOOKUP_TABLE override the "tomato" color that is specified by the "vtkProperty" module of the VisTrails pipeline. The default "tomato" color can be retrieved without modifying the new input datafile by clicking on (i.e., selecting) the "vtkPolyDataMapper" module in the VisTrails pipeline, dragging the "ScalarVisibilityOff" method into the "Set Methods" segment of the VisTrials Builder Window, then reexecuting the pipeline.		</table>
			</div>
	<~~font color="red"~~>~~'''Comment#3 (by J. E. Tohline):'''~~</~~font~~> Example C, shown here, adopts the same CELL_DATA scalar values that appear in the simple "cube example" presented in §15.3 (see the top of p. 332) of the [http://www.kitware.com/products/books/vtkguide.html ''VTK User's Guide'']. In my opinion, this was a very odd choice to make if its purpose was to help students understand how the VTK and/or VisTrails machinery works. I, for one, was pretty sure I was still doing something wrong when I was finally able to read the "cube example" file into the VisTrails "vtkPolyDataReader," because most of the faces of the cube were painted the same color (blue) whereas I was expecting them all to have different, illustrative colors.

	===Specifying Colors of Cell Faces via a User-defined Color Table===		===Specifying Colors of Cell Faces via a User-defined Color Table===

Tohline: /* Other Example Input Files and VisTrails Pipelines */ Add orange color to "XML" labeling

2014-04-20T20:36:43Z

Other Example Input Files and VisTrails Pipelines: Add orange color to "XML" labeling

← Older revision		Revision as of 20:36, 20 April 2014
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	==Simple Legacy Format==		==Simple Legacy Format==
	* [[User:Tohline/vtk/Examples/LegacyCubeG#Example_Input_Files_.26_VisTrails_Pipelines\|Cube Example G]]: Uses ~~vtkPolyDataReader~~ & ~~vtkPolyDataMapper~~		* [[User:Tohline/vtk/Examples/LegacyCubeG#Example_Input_Files_.26_VisTrails_Pipelines\|Cube Example G]]: Uses vtk<font color="red">PolyData</font>Reader & vtk<font color="red">PolyData</font>Mapper
	* [[User:Tohline/vtk/Examples/LegacyBUstructuredPoints\|BU (Robert Putnam) Example of Structured Points]]: Uses vtk<font color="red">StructuredPoints</font>Reader & vtk<font color="red">DataSet</font>Mapper		* [[User:Tohline/vtk/Examples/LegacyBUstructuredPoints\|BU (Robert Putnam) Example of Structured Points]]: Uses vtk<font color="red">StructuredPoints</font>Reader & vtk<font color="red">DataSet</font>Mapper
	* [[User:Tohline/vtk/Examples/LegacyCornellRectGrid\|Cornell Example of Rectilinear Grid]]: Uses vtk<font color="red">RectilinearGrid</font>Reader & vtk<font color="red">DataSet</font>Mapper		* [[User:Tohline/vtk/Examples/LegacyCornellRectGrid\|Cornell Example of Rectilinear Grid]]: Uses vtk<font color="red">RectilinearGrid</font>Reader & vtk<font color="red">DataSet</font>Mapper

	==XML-Formatted==		==XML-Formatted==
	* [[User:Tohline/vtk/Examples/XMLwarpedQuilt#Example_Input_Files_.26_VisTrails_Pipelines\|Warped Quilt]]: Uses ~~vtkXMLPolyDataReader~~, vtkWarpScalar, & ~~vtkXMLPolyDataMapper~~		* [[User:Tohline/vtk/Examples/XMLwarpedQuilt#Example_Input_Files_.26_VisTrails_Pipelines\|Warped Quilt]]: Uses vtk<font color="orange">XML</font><font color="red">PolyData</font>Reader, vtkWarpScalar, & vtk<font color="orange">XML</font><font color="red">PolyData</font>Mapper
	* Rectilinear Grid: Uses ~~vtkXML~~<font color="red">RectilinearGrid</font>Reader, vtkWarpScalar, & ~~vtkXML~~<font color="red">DataSet</font>Mapper		* Rectilinear Grid: Uses vtk<font color="orange">XML</font><font color="red">RectilinearGrid</font>Reader, vtkWarpScalar, & vtk<font color="orange">XML</font><font color="red">DataSet</font>Mapper
	** [[User:Tohline/vtk/Examples/XMLRectilinearGrid#XML_.28RectilinearGrid.29_Warped_Quilt_Example\|Warped Quilt]] (6 x 6 grid)		** [[User:Tohline/vtk/Examples/XMLRectilinearGrid#XML_.28RectilinearGrid.29_Warped_Quilt_Example\|Warped Quilt]] (6 x 6 grid)
	** [[User:Tohline/vtk/Examples/XMLRectilinearGrid#XML_.28RectilinearGrid.29_Mexican_Hat_Example\|Mexican Hat]] at two different resolutions: (50 x 50 grid) and (10 x 10 grid); the lower resolution example also illustrates how the '''vtkWarpScalar''' module handles user-specified Normals.		** [[User:Tohline/vtk/Examples/XMLRectilinearGrid#XML_.28RectilinearGrid.29_Mexican_Hat_Example\|Mexican Hat]] at two different resolutions: (50 x 50 grid) and (10 x 10 grid); the lower resolution example also illustrates how the '''vtkWarpScalar''' module handles user-specified Normals.

Tohline: /* Simple Legacy Format */ Add link to Cornell RectilinearGrid example

2014-04-20T18:25:14Z

Simple Legacy Format: Add link to Cornell RectilinearGrid example

← Older revision		Revision as of 18:25, 20 April 2014
Line 1,255:		Line 1,255:
	* [[User:Tohline/vtk/Examples/LegacyCubeG#Example_Input_Files_.26_VisTrails_Pipelines\|Cube Example G]]: Uses vtkPolyDataReader & vtkPolyDataMapper		* [[User:Tohline/vtk/Examples/LegacyCubeG#Example_Input_Files_.26_VisTrails_Pipelines\|Cube Example G]]: Uses vtkPolyDataReader & vtkPolyDataMapper
	* [[User:Tohline/vtk/Examples/LegacyBUstructuredPoints\|BU (Robert Putnam) Example of Structured Points]]: Uses vtk<font color="red">StructuredPoints</font>Reader & vtk<font color="red">DataSet</font>Mapper		* [[User:Tohline/vtk/Examples/LegacyBUstructuredPoints\|BU (Robert Putnam) Example of Structured Points]]: Uses vtk<font color="red">StructuredPoints</font>Reader & vtk<font color="red">DataSet</font>Mapper
			* [[User:Tohline/vtk/Examples/LegacyCornellRectGrid\|Cornell Example of Rectilinear Grid]]: Uses vtk<font color="red">RectilinearGrid</font>Reader & vtk<font color="red">DataSet</font>Mapper

	==XML-Formatted==		==XML-Formatted==

← Older revision		Revision as of 20:36, 20 April 2014
Line 1,253:		Line 1,253:

	==Simple Legacy Format==		==Simple Legacy Format==
	* [[User:Tohline/vtk/Examples/LegacyCubeG#Example_Input_Files_.26_VisTrails_Pipelines\|Cube Example G]]: Uses ~~vtkPolyDataReader~~ & ~~vtkPolyDataMapper~~		* [[User:Tohline/vtk/Examples/LegacyCubeG#Example_Input_Files_.26_VisTrails_Pipelines\|Cube Example G]]: Uses vtk<font color="red">PolyData</font>Reader & vtk<font color="red">PolyData</font>Mapper
	* [[User:Tohline/vtk/Examples/LegacyBUstructuredPoints\|BU (Robert Putnam) Example of Structured Points]]: Uses vtk<font color="red">StructuredPoints</font>Reader & vtk<font color="red">DataSet</font>Mapper		* [[User:Tohline/vtk/Examples/LegacyBUstructuredPoints\|BU (Robert Putnam) Example of Structured Points]]: Uses vtk<font color="red">StructuredPoints</font>Reader & vtk<font color="red">DataSet</font>Mapper
	* [[User:Tohline/vtk/Examples/LegacyCornellRectGrid\|Cornell Example of Rectilinear Grid]]: Uses vtk<font color="red">RectilinearGrid</font>Reader & vtk<font color="red">DataSet</font>Mapper		* [[User:Tohline/vtk/Examples/LegacyCornellRectGrid\|Cornell Example of Rectilinear Grid]]: Uses vtk<font color="red">RectilinearGrid</font>Reader & vtk<font color="red">DataSet</font>Mapper

	==XML-Formatted==		==XML-Formatted==
	* [[User:Tohline/vtk/Examples/XMLwarpedQuilt#Example_Input_Files_.26_VisTrails_Pipelines\|Warped Quilt]]: Uses ~~vtkXMLPolyDataReader~~, vtkWarpScalar, & ~~vtkXMLPolyDataMapper~~		* [[User:Tohline/vtk/Examples/XMLwarpedQuilt#Example_Input_Files_.26_VisTrails_Pipelines\|Warped Quilt]]: Uses vtk<font color="orange">XML</font><font color="red">PolyData</font>Reader, vtkWarpScalar, & vtk<font color="orange">XML</font><font color="red">PolyData</font>Mapper
	* Rectilinear Grid: Uses ~~vtkXML~~<font color="red">RectilinearGrid</font>Reader, vtkWarpScalar, & ~~vtkXML~~<font color="red">DataSet</font>Mapper		* Rectilinear Grid: Uses vtk<font color="orange">XML</font><font color="red">RectilinearGrid</font>Reader, vtkWarpScalar, & vtk<font color="orange">XML</font><font color="red">DataSet</font>Mapper
	** [[User:Tohline/vtk/Examples/XMLRectilinearGrid#XML_.28RectilinearGrid.29_Warped_Quilt_Example\|Warped Quilt]] (6 x 6 grid)		** [[User:Tohline/vtk/Examples/XMLRectilinearGrid#XML_.28RectilinearGrid.29_Warped_Quilt_Example\|Warped Quilt]] (6 x 6 grid)
	** [[User:Tohline/vtk/Examples/XMLRectilinearGrid#XML_.28RectilinearGrid.29_Mexican_Hat_Example\|Mexican Hat]] at two different resolutions: (50 x 50 grid) and (10 x 10 grid); the lower resolution example also illustrates how the '''vtkWarpScalar''' module handles user-specified Normals.		** [[User:Tohline/vtk/Examples/XMLRectilinearGrid#XML_.28RectilinearGrid.29_Mexican_Hat_Example\|Mexican Hat]] at two different resolutions: (50 x 50 grid) and (10 x 10 grid); the lower resolution example also illustrates how the '''vtkWarpScalar''' module handles user-specified Normals.