SoTextureCombine(3)

NAME
SoTextureCombine - The SoTextureCombine class is a node for setting texture combine functions.

This node is more or less an exact mapping of the OpenGL ARB_texture_env_combine extension (included in OpenGL in OpenGL v1.3). See http://oss.sgi.com/projects/ogl-sample/registry/ARB/texture_env_combine.txt for more information about this extension.

SYNOPSIS

#include <Inventor/nodes/SoTextureCombine.h>

Inherits SoNode.

  Public Types
enum Source { PRIMARY_COLOR = SoTextureCombineElement::PRIMARY_COLOR, TEXTURE = SoTextureCombineElement::TEXTURE, CONSTANT = SoTextureCombineElement::CONSTANT, PREVIOUS = SoTextureCombineElement::PREVIOUS }
enum Operand { SRC_COLOR = SoTextureCombineElement::SRC_COLOR, ONE_MINUS_SRC_COLOR = SoTextureCombineElement::ONE_MINUS_SRC_COLOR, SRC_ALPHA = SoTextureCombineElement::SRC_ALPHA, ONE_MINUS_SRC_ALPHA = SoTextureCombineElement::ONE_MINUS_SRC_ALPHA }
enum Operation { REPLACE = SoTextureCombineElement::REPLACE, MODULATE = SoTextureCombineElement::MODULATE, ADD = SoTextureCombineElement::ADD, ADD_SIGNED = SoTextureCombineElement::ADD_SIGNED, SUBTRACT = SoTextureCombineElement::SUBTRACT, INTERPOLATE = SoTextureCombineElement::INTERPOLATE, DOT3_RGB = SoTextureCombineElement::DOT3_RGB, DOT3_RGBA = SoTextureCombineElement::DOT3_RGBA }

  Public Member Functions
virtual SoType getTypeId (void) const
SoTextureCombine (void)
virtual void doAction (SoAction *action)
virtual void callback (SoCallbackAction *action)
virtual void GLRender (SoGLRenderAction *action)
virtual void pick (SoPickAction *action)

  Static Public Member Functions
static SoType getClassTypeId (void)
static void initClass (void)

  Public Attributes
SoMFEnum rgbSource
SoMFEnum alphaSource
SoMFEnum rgbOperand
SoMFEnum alphaOperand
SoSFEnum rgbOperation
SoSFEnum alphaOperation
SoSFFloat rgbScale
SoSFFloat alphaScale
SoSFVec4f constantColor

  Protected Member Functions
virtual const SoFieldData * getFieldData (void) const
virtual ~SoTextureCombine ()

  Static Protected Member Functions
static const SoFieldData ** getFieldDataPtr (void)

  Additional Inherited Members

Detailed Description

The SoTextureCombine class is a node for setting texture combine functions.

This node is more or less an exact mapping of the OpenGL ARB_texture_env_combine extension (included in OpenGL in OpenGL v1.3). See http://oss.sgi.com/projects/ogl-sample/registry/ARB/texture_env_combine.txt for more information about this extension. Basically this node lets you specify up to three sources, and a function to combine those sources. In addition to the function, it's possible to apply simple operands on the sources. In the documentation below, the sources will be called Arg0, Arg1, and Arg2, just like in the ARB_texture_env_mode specification.

It's possible to specify both a color and an alpha operation.

This node has many fields, but usually it is sufficient to set only one or very few fields. The selected operation decides which values you need to set. One common example is to add a light map to textured geometry. A lightmap can look like this:

The example below just shows how to apply the lightmap to a cube, with one light source on each side of the cube. Usually the texture coordinates are calculated so that a spot light or a point light is simulated.

Texture2 { filename "wood.jpg" }
Switch {
  whichChild -3   # use to toggle lightmap on/off
  TextureUnit {
    unit 1
  }
  TextureCombine {
    rgbOperation ADD_SIGNED
    rgbSource [PREVIOUS, TEXTURE]
    rgbOperand [SRC_COLOR, SRC_COLOR ]
    alphaOperation REPLACE
    alphaSource [TEXTURE]
    alphaOperand [SRC_ALPHA]
  }
  Texture2 { filename "lightmap.jpg" }
  TextureUnit { unit 0 }
}
Cube { }.fi

The scene above in a viewer:

In addition to the functions you can set in rgbOperation (or alphaOperation), it's possible to create more complex texture functions by combining two textures that have already been combined. You can use the SoSceneTexture2 node to create those textures. Below is an example that shows how to implement Arg0*Arg1

•   Arg2*Arg0, where Arg0 = texture1 RGB, Arg1 = texture2 RGB, Arg2 = texture 2 alpha:

ShapeHints { vertexOrdering COUNTERCLOCKWISE shapeType SOLID }
Separator {
  SceneTexture2 {
    size 256 256
    transparencyFunction NONE
    scene Separator {
      OrthographicCamera {
        height 2
        aspectRatio 1
        position 0 0 1
        viewportMapping LEAVE_ALONE
      }
      LightModel { model BASE_COLOR }
      Coordinate3 {
        point [ -1 -1 0, 1 -1 0, 1 1 0, -1 1 0 ]
      }
      DEF texture1 Texture2 { filename "texture1.png" }
      TextureUnit { unit 1 }
      TextureCombine {
        rgbOperation MODULATE
        rgbSource [ PREVIOUS, TEXTURE ]
        rgbOperand [ SRC_COLOR, SRC_COLOR ]
        alphaOperation REPLACE
        alphaSource [TEXTURE]
        alphaOperand [ SRC_ALPHA ]
      }
      DEF texture2 Texture2 { filename "texture2_with_alpha.png" }
      TextureCoordinate2 {
        point [0 0, 1 0, 1 1, 0 1]
      }
      FaceSet { numVertices 4 }
    }
  }
  TextureUnit { unit 1 }
  TextureCombine {
    rgbOperation ADD
    rgbSource [ PREVIOUS, TEXTURE ]
    rgbOperand [ SRC_COLOR, SRC_COLOR ]
    alphaOperation REPLACE
    alphaSource [TEXTURE]
    alphaOperand [ SRC_ALPHA ]
  }
  SceneTexture2 {
    size 256 256
    transparencyFunction NONE
    scene Separator {
      OrthographicCamera {
        height 2
        aspectRatio 1
        position 0 0 1
        viewportMapping LEAVE_ALONE
      }
      LightModel { model BASE_COLOR }
      Coordinate3 {
        point [ -1 -1 0, 1 -1 0, 1 1 0, -1 1 0 ]
      }
      USE texture1
      TextureUnit { unit 1 }
      TextureCombine {
        rgbOperation MODULATE
        rgbSource [ PREVIOUS, TEXTURE ]
        rgbOperand [ SRC_COLOR, SRC_ALPHA ]
        alphaOperation REPLACE
        alphaSource [TEXTURE]
        alphaOperand [ SRC_ALPHA ]
      }
      USE texture2
      TextureCoordinate2 {
        point [0 0, 1 0, 1 1, 0 1]
      }
      FaceSet { numVertices 4 }
    }
  }
  # map resulting texture onto a Cube
  Cube { }
}

It should be possible to create almost any kind of texture function using this scheme, at the cost of extra texture memory usage (the intermediate textures), of course.

FILE FORMAT/DEFAULTS:

TextureCombine {
    rgbSource [  ]
    alphaSource [  ]
    rgbOperand [  ]
    alphaOperand [  ]
    rgbOperation MODULATE
    alphaOperation MODULATE
    rgbScale 1
    alphaScale 1
    constantColor 1 1 1 1
}

Since:
    Coin 2.3

Member Enumeration Documentation

  enum SoTextureCombine::Source
For enumerating combiner sources.

Enumerator

PRIMARY_COLOR
    Choose primary color as source.

TEXTURE
    Choose texture as source.

CONSTANT
    Choose the constantColor field as source.

PREVIOUS
    Choose the previous unit's texture as source.

  enum SoTextureCombine::Operand
For enumerating source operands.

Enumerator

SRC_COLOR
    Use the source color as operand.

ONE_MINUS_SRC_COLOR
    Use one minus source color as operand.

SRC_ALPHA
    Use the source alpha as operand.

ONE_MINUS_SRC_ALPHA
    Use one minus source alpha as operand.

  enum SoTextureCombine::Operation
For enumerating combiner operations/functions.

Enumerator

REPLACE
    dst = Arg0

MODULATE
    dst = Arg0 * Arg1

ADD dst = Arg0 + Arg1

ADD_SIGNED
    dst = Arg0 + Arg1 - 0.5

SUBTRACT
    dst = Arg0 - Arg1

INTERPOLATE
    dst = Arg0 * (Arg2) + Arg1 * (1-Arg2)

DOT3_RGB
    Dot product of Arg0 and Arg1

DOT3_RGBA
    Dot product (including alpha) of Arg0 and Arg1

Constructor & Destructor Documentation

  SoTextureCombine::SoTextureCombine (void)
Constructor.

  SoTextureCombine::~SoTextureCombine () [protected], [virtual]
Destructor.

Member Function Documentation

  SoType SoTextureCombine::getClassTypeId (void) [static]
SoTextureCombine::rgbSource

The color sources. This field is empty by default, but you can insert up to three values [Arg0, Arg1, Arg2]. When the field contains less than three values, the default [TEXTURE, PREVIOUS, CONSTANT], will be used for missing values.

For texture unit 0, PREVIOUS maps to PRIMARY_COLOR,

SoTextureCombine::alphaSource

The alpha sources. This field is empty by default, but you can insert up to three values [Arg0, Arg1, Arg2]. When the field contains less than three values, the default [TEXTURE, PREVIOUS, CONSTANT], will be used for missing values.

For texture unit 0, PREVIOUS maps to PRIMARY_COLOR,

SoTextureCombine::rgbOperand

The color operands. This field is empty by default, but you can insert up to three values. When the field contains less than three values, the default [SRC_COLOR, SRC_COLOR, SRC_COLOR] will be used for missing values.

SoTextureCombine::alphaOperand

The alpha operands. This field is empty by default, but you can insert up to three values. When the field contains less than three values, the default [SRC_ALPHA, SRC_ALPHA, SRC_ALPHA] will be used for missing values. Please not that only SRC_ALPHA and ONE_MINUS_SRC_ALPHA are valid operands for alpha operations.

SoTextureCombine::rgbOperation

The color operation. Default value is MODULATE.

SoTextureCombine::alphaOperation

The alpha operation. Default value is MODULATE.

SoTextureCombine::rgbScale

Scale color result by this value. Supported values are 1, 2, and 4.

SoTextureCombine::alphaScale

Scale alpha result by this value. Supported values are 1, 2, and 4.

SoTextureCombine::constantColor

The constant color (when CONSTANT is used as source). Default value is (1,1,1,1).

  SoType SoTextureCombine::getTypeId (void) const [virtual]
Returns the type identification of an object derived from a class inheriting SoBase. This is used for run-time type checking and 'downward' casting.

Usage example:

void foo(SoNode * node)
{
  if (node->getTypeId() == SoFile::getClassTypeId()) {
    SoFile * filenode = (SoFile *)node;  // safe downward cast, knows the type
  }
}

For application programmers wanting to extend the library with new nodes, engines, nodekits, draggers or others: this method needs to be overridden in all subclasses. This is typically done as part of setting up the full type system for extension classes, which is usually accomplished by using the pre-defined macros available through for instance Inventor/nodes/SoSubNode.h (SO_NODE_INIT_CLASS and SO_NODE_CONSTRUCTOR for node classes), Inventor/engines/SoSubEngine.h (for engine classes) and so on.

For more information on writing Coin extensions, see the class documentation of the toplevel superclasses for the various class groups.

Implements SoBase.

  const SoFieldData * SoTextureCombine::getFieldData (void) const [protected], [virtual]
Returns a pointer to the class-wide field data storage object for this instance. If no fields are present, returns NULL.

Reimplemented from SoFieldContainer.

  void SoTextureCombine::doAction (SoAction * action) [virtual]
This function performs the typical operation of a node for any action.

Reimplemented from SoNode.

  void SoTextureCombine::callback (SoCallbackAction * action) [virtual]
Action method for SoCallbackAction.

Simply updates the state according to how the node behaves for the render action, so the application programmer can use the SoCallbackAction for extracting information about the scene graph.

Reimplemented from SoNode.

  void SoTextureCombine::GLRender (SoGLRenderAction * action) [virtual]
Action method for the SoGLRenderAction.

This is called during rendering traversals. Nodes influencing the rendering state in any way or who wants to throw geometry primitives at OpenGL overrides this method.

Reimplemented from SoNode.

  void SoTextureCombine::pick (SoPickAction * action) [virtual]
Action method for SoPickAction.

Does common processing for SoPickAction action instances.

Reimplemented from SoNode.

Author

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