SoTextureCombine -

#include <Inventor/nodes/SoTextureCombine.h>

Inherits SoNode.

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 { } } .fi

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

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Protected Member Functions

Static Protected Member Functions

enum SoTextureCombine::Source

enum SoTextureCombine::Operand

enum SoTextureCombine::Operation

SoTextureCombine::SoTextureCombine (void)

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

SoType SoTextureCombine::getClassTypeId (void) [static]

SoType SoTextureCombine::getTypeId (void) const [virtual]

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

const SoFieldData ** SoTextureCombine::getFieldDataPtr (void) [static, protected]

const SoFieldData * SoTextureCombine::getFieldData (void) const [protected, virtual]

void SoTextureCombine::initClass (void) [static]

void SoTextureCombine::doAction (SoAction * action) [virtual]

void SoTextureCombine::callback (SoCallbackAction * action) [virtual]

void SoTextureCombine::GLRender (SoGLRenderAction * action) [virtual]

void SoTextureCombine::pick (SoPickAction * action) [virtual]

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