Controlling Color on Coordinate-Based Geometry

Motivation

• The Material node gives an entire shape the same color
• You can provide colors for individual parts of a shape using a Color node

Syntax: Color

A Color node contains a list of RGB values (similar to a Coordinate node):

XML Encoding

<Color
    color='1.0 0.0 0.0, ...'/>

Classic VRML Encoding

Color {
  color [ 1.0 0.0 0.0, ... ]
}

Used as the color field value of IndexedFaceSet, IndexedLineSet, PointSet or ElevationGrid nodes.

Binding colors

• Colors in the Color node override those in the Material node
• You can bind colors
  • To each point, line, or face
  • To each coordinate in a line, or face

Syntax: PointSet

A PointSet geometry node creates geometry out of points:

• color - provides a list of colors
• Always binds one color to each point, in order

XML Encoding

<Shape>
  <Appearance><!-- ... --></Appearance>
  <PointSet>
    <Color ... />
    <Coordinate ... />
  </PointSet>
</Shape>

Classic VRML Encoding

Shape {
  appearance Appearance { ... }
  geometry PointSet {
    color Color { ... }
    coord Coordinate { ... }
  }
}

Syntax: IndexedLineSet

An IndexedLineSet geometry node creates geometry out of lines:

• color - list of colors
• colorIndex - selects colors from list
• colorPerVertex - control color binding

XML Encoding

<Shape>
  <Appearance><!-- ... --></Appearance>
  <IndexedLineSet
      colorPerVertex='true'
      colorIndex='...'
      coordIndex='...'>
    <Color ... />
    <Coordinate ... />
  </IndexedLineSet>
</Shape>

Classic VRML Encoding

Shape {
  appearance Appearance { ... }
  geometry IndexedLineSet {
    colorPerVertex TRUE
    colorIndex [ ... ]
    coordIndex [ ... ]
    color Color { ... }
    coord Coordinate { ... }
  }
}

Controlling color binding for line sets

The colorPerVertex field controls how color indexes are used:

• FALSE: one color index to each line (ending at -1 coordinate indexes)
• TRUE: one color index to each coordinate index of each line (including -1 coordinate indexes)

Syntax: IndexedFaceSet

An IndexedFaceSet geometry node creates geometry out of faces:

• color - list of colors
• colorIndex - selects colors from list
• colorPerVertex - control color binding

XML Encoding

<Shape>
  <Appearance><!-- ... --></Appearance>
  <IndexedFaceSet
      colorPerVertex='true'
      colorIndex='...'
      coordIndex='...'>
    <Color ... />
    <Coordinate ... />
  </IndexedFaceSet>
</Shape>

Classic VRML Encoding

Shape {
  appearance Appearance { ... }
  geometry IndexedFaceSet {
    colorPerVertex TRUE
    colorIndex [ ... ]
    coordIndex [ ... ]
    color Color { ... }
    coord Coordinate { ... }
  }
}

Controlling color binding for face sets

The colorPerVertex field controls how color indexes are used (similar to line sets):

• FALSE: one color index to each face (ending at -1 coordinate indexes)
• TRUE: one color index to each coordinate index of each face (including -1 coordinate indexes)

Syntax: ElevationGrid

An ElevationGrid geometry node creates terrains:

• color - list of colors
• colorPerVertex - control color binding
• Always binds one color to each grid point or square, in order

XML Encoding

<Shape>
  <Appearance><!-- ... --></Appearance>
  <ElevationGrid
      ...
      colorPerVertex='true'
      height='...'>
    <Color ... />
  </ElevationGrid>
</Shape>

Classic VRML Encoding

Shape {
  appearance Appearance { ... }
  geometry ElevationGrid {
    ...
    colorPerVertex TRUE
    color Color { ... }
    height [ ... ]
  }
}

Controlling color binding for elevation grids

The colorPerVertex field controls how color indexes are used (similar to line and face sets):

• FALSE: one color to each grid square
• TRUE: one color to each height for each grid square

Summary

The Color node lists colors to use for parts of a shape:

• Used as the value of the color field
• Color indexes select colors to use
• Colors override Material node

The colorPerVertex field selects color per line/face/grid square or color per coordinate.