SoShaderObject Class Reference
[Shaders]

Abstract node class which defines a shader object. More...

#include <Inventor/nodes/SoShaderObject.h>

Inheritance diagram for SoShaderObject:

List of all members.

Public Types
enum	SourceType {   ARB_PROGRAM,   CG_PROGRAM,   GLSL_PROGRAM,   FILENAME }
enum	ShaderType {   VERTEX_SHADER,   GEOMETRY_SHADER,   FRAGMENT_SHADER,   TESSELLATION_CONTROL_SHADER,   TESSELLATION_EVALUATION_SHADER }
Public Member Functions
virtual SoType	getTypeId () const
template<typename UniformParamType , typename ParamValueType >
UniformParamType *	addShaderParameter (const SbString &name, ParamValueType val)
virtual ShaderType	getShaderType () const =0
template<typename UniformParamType , typename ParamValueType >
void	setShaderParameter (const SbString &name, ParamValueType val)
Static Public Member Functions
static SoType	getClassTypeId ()
Public Attributes
SoSFBool	isActive
SoSFEnum	sourceType
SoSFFilePathString	sourceProgram
SoMFUniformShaderParameter	parameter
Friends
class	SoShaderProgram

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Detailed Description

Abstract node class which defines a shader object.

This abstract class is the parent of classes that define a vertex shader (SoVertexShader), a geometry shader (SoGeometryShader), a fragment shader (SoFragmentShader), a tessellation control shader (SoTessellationControlShader) or a tessellation evaluation shader (SoTessellationEvaluationShader) program. (Tessellation shaders are supported since Open Inventor 9.3)

There are five types of shaders that may be executed (in this order) in the rendering pipeline. Any one or all of these stages may be replaced by an application defined shader program.

• Vertex shader
  The vertex shader is executed once for each vertex (usually in parallel). The purpose is to transform each vertex's 3D position in virtual space to the 2D coordinate at which it appears on the screen (as well as a depth value for the Z-buffer). Vertex shaders can manipulate properties such as position, color and texture coordinate, but cannot create new vertices.

• Tessellation control shader
  This shader accepts a list of vertices defining a patch from the vertex shader and controls the amount of tessellation applied to the patch. Following execution of this shader, a fixed tesselator computes a set of triangles in a parametric space.

• Tessellation evaluation shader
  This shader is executed at least once for each vertex that was created by the tesselator in the parametric space. The TES takes the parametric coordinate and the patch data output by the TCS to generate a final position for the surface.

• Geometry shader
  The geometry shader acts on a complete primitive (triangle or line): it can modify existing primitives, it can insert (create) new primitives, it can remove (destroy) existing primitives.

• Fragment shader
  Fragment shaders compute color and other attributes of each fragment.

Shader object nodes cannot be inserted directly in a scene graph. They must be added to the shaderObject field of an SoShaderProgram node.

A shader object is defined by the following properties:

• Source program, which is the shader's source code (see sourceProgram field),
• Uniform parameters set by the application (see parameter field),
• State (active or not) (see isActive field).

The source program can be specified either by a string containing the program source code, or by a filename which contains the program source code. How the sourceProgram field is interpreted depends on the field sourceType. The shading languages accepted for the source program are OpenGL Shader Language (GLSL) , Cg from NVIDIA (see NOTE 1) and assembly language ( ARB_vertex_program, ARB_fragment_program). Generally GLSL is recommended because it works on any OpenGL hardware and is much higher level than the ARB commands.

Uniform parameters can be set through the parameter field. Uniform means, in the case of a vertex or geometry program, a value which is the same for all vertices in a primitive, and, in the case of a fragment program, a value which is the same for all fragments created by a primitive. Each uniform parameter is represented by an instance of a specific subclass of SoUniformShaderParameter. For example, an SoShaderParameter1i holds a single integer value. A uniform parameter has no effect if it is not valid, that is, if there is no corresponding name (identifier) in the CG/GLSL (ARB) source program. See NOTE 2 for info on retrieving a texture sampler uniform parameter within a GLSL program, an NVIDIA Cg fragment program, or an ARB_vertex_program/ARB_fragment_program program.

A vertex shader can also use vertex parameters, which are per-vertex data passed from the application to the vertex shader. Vertex parameters are represented by an instance of a specific subclass of SoVertexShaderParameter. For example, an SoVertexShaderParameter1f holds a set of floating point values and an SoVertexShaderParameter3f holds a set of SbVec3f values. Vertex parameter nodes are property nodes (similar to materials or normals) and should be added directly in the scene graph, not in the shader object.

Tips:

• When using GLSL shaders, set the environment variable OIV_GLSL_DEBUG to get the GLSL compile/link output in the console.

• If you set the environment variable OIV_SHADER_CHECK_INTERVAL, the shader source file is checked for a change every n seconds, where n is the value specified by the variable. This allows you to edit a shader source file without needing to restart your application after each shader modification.

NOTE 1: In case of Cg, the default profile used for the vertex shader is arbvp1, and arbfp1 for a fragment shader. The environment variables OIV_CG_VTX_PROFILE and OIV_CG_FRAG_PROFILE enable you to change the vertex and fragment profiles respectively. However, we advise users to use the default profile because it enables you to retrieve the OpenGL state directly in your vertex/fragment program instead of passing the OpenGL state as uniform parameters, which could be inefficient in terms of performance.

NOTE 2: With NVIDIA Cg and ARB_vertex_program/ARB_fragment_program, a texture sampler can be retrieved in your fragment program without specifying any SoShaderParameter parameter.

• With ARB_vertex_program/ARB_fragment_program, texture[i] corresponds to the texture sampler of unit i.

• With NVIDIA Cg, the first texture sampler parameter in your fragment program corresponds to the texture sampler of the texture unit 0, the second texture sampler parameter to the texture sampler of the texture unit 1, and so on.
  Example:

       void  main(// Inputs
                  Input IN,
                  uniform sampler2D rampDiffuse,   // Texture sampler 2D of the texture unit 0
                  uniform sampler2D rampSpecular,  // Texture sampler 2D of the texture unit 1
                  uniform sampler2D rampEdge,      // Texture sampler 2D of the texture unit 2
                  ...
  

• With GLSL, an SoShaderParameter1i must used for each texture sampler in order to specify the texture unit and texture sampler uniform parameter name pair.

NOTE 3: With Cg and ARB languages, at least the ARB_vertex_program and ARB_fragment_program, and with GLSL, at least GL_ARB_vertex_shader, GL_ARB_fragment_shader, and GL_ARB_shader_objects OpenGL extensions must be supported by your graphics board in order to be able to define a vertex shader and a fragment shader respectively. Otherwise no shader program will be executed.

NOTE 4: You should keep in mind that vertex and fragment programs modify the standard OpenGL pipeline.

• Vertex programs replace the following parts of the OpenGL graphics pipeline:
  • Vertex transformation,
  • Normal transformation normalization and rescaling,
  • Lighting,
  • Color material application,
  • Clamping of colors,
  • Texture coordinate generation,
  • Texture coordinate transformation.

• But do not replace:
  • Perspective divide and viewport mapping,
  • Frustum and user clipping,
  • Backface culling,
  • Primitive assembly,
  • Two sided lighting selection,
  • Polygon offset,
  • Polygon mode.

• Fragment programs replace the following parts of the OpenGL graphics pipeline:
  • Operations on interpolated values,
  • Pixel zoom,
  • Texture access,
  • Scale and bias,
  • Texture application,
  • Color table lookup,
  • Fog convolution,
  • Color sum,
  • Color matrix.

• But do not replace:
  • Shading model,
  • Histogram,
  • Coverage,
  • Minmax,
  • Pixel ownership test,
  • Pixel packing and unpacking,
  • Scissor,
  • Stipple,
  • Alpha test,
  • Depth test,
  • Stencil test,
  • Alpha blending,
  • Logical ops,
  • Dithering,
  • Plane masking.

FILE FORMAT/DEFAULT

This is an abstract class. See the reference page of a derived class for the format and default values.

EXAMPLE

Simple fragment shader with one uniform parameter:

   // First load the fragment shader code
   SoFragmentShader* fragmentShader = new SoFragmentShader();
   fragmentShader->sourceProgram = "filename.glsl";

   // Set a shader parameter
   // The addShaderParameter1i method is equivalent to:
   //     SoShaderParameter1i *parameter = new SoShaderParameter1i;
   //     parameter->name  = "data1";
   //     parameter->value = 1;
   //     fragmentShader->parameter.set1Value(0, parameter);
   fragmentShader->addShaderParameter1i( "data1", 1 );

   // Associate fragment shader with a shader program node
   SoShaderProgram* shaderProgram = new SoShaderProgram();
   shaderProgram->shaderObject.set1Value(0, fragmentShader);
   root->addChild( shaderProgram );

SEE ALSO

SoVertexShader, SoGeometryShader, SoFragmentShader, SoShaderProgram, SoShaderParameter, SoUniformShaderParameter, SoVertexShaderParameter, SoTessellationControlShader, SoTessellationEvaluationShader

See related examples:

ShadersBrowser, AnimatedFlag, GeometryShader, PixelLighting, shadowShader, TessellationShader, ToonShading

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Member Enumeration Documentation

enum SoShaderObject::ShaderType

Type of the shader.

Enumerator:

VERTEX_SHADER	The shader is a vertex shader.
GEOMETRY_SHADER	The shader is a geometry shader.
FRAGMENT_SHADER	The shader is a fragment shader.
TESSELLATION_CONTROL_SHADER	The shader is a tessellation control shader.
TESSELLATION_EVALUATION_SHADER	The shader is a tessellation evaluation shader.

enum SoShaderObject::SourceType

Shader Object source type possible values.

Enumerator:

ARB_PROGRAM	The source is an ARB vertex or fragment program.
CG_PROGRAM	The source is a CG program.
GLSL_PROGRAM	The source is an OpenGL Shading Language program.
FILENAME	Only the name of the file containing the source is given (default).

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Member Function Documentation

template<typename UniformParamType , typename ParamValueType >

UniformParamType * SoShaderObject::addShaderParameter	(	const SbString &	name,
		ParamValueType	val
	)			[inline]

Convenience method to create an SoShaderUniformParameter with the specified name and value and add it to the given shader object.

UniformParamType is the type of parameter to add. This function also generates the following helper methods not visible in the documentation:

• UniformParamType* addShaderParameter{1,2,3,4}i(const SbString&, ParamValueType)
• UniformParamType* addShaderParameter{1,2,3,4}f(const SbString&, ParamValueType)
• UniformParamType* addShaderParameterArray{1,2,3,4}i(const SbString&, ParamValueType)
• UniformParamType* addShaderParameterArray{1,2,3,4}f(const SbString&, ParamValueType)
• UniformParamType* addShaderParameterMatrix

These are template methods, so ParamValueType must have an operator= compatible with the field value of the corresponding SoShaderParameter (for example, addShaderParameter2f can take an SbVec2f as ParamValueType)

static SoType SoShaderObject::getClassTypeId

(

)

[static]

Returns the type identifier for this class.

Reimplemented from SoNode.

Reimplemented in SoFragmentShader, SoGeometryShader, SoTessellationControlShader, SoTessellationEvaluationShader, and SoVertexShader.

virtual ShaderType SoShaderObject::getShaderType

(

)

const [pure virtual]

Must be redefined by derived class.

Implemented in SoFragmentShader, SoGeometryShader, SoTessellationControlShader, SoTessellationEvaluationShader, and SoVertexShader.

virtual SoType SoShaderObject::getTypeId

(

)

const [virtual]

Returns the type identifier for this specific instance.

Reimplemented from SoNode.

Reimplemented in SoFragmentShader, SoGeometryShader, SoTessellationControlShader, SoTessellationEvaluationShader, and SoVertexShader.

template<typename UniformParamType , typename ParamValueType >

void SoShaderObject::setShaderParameter	(	const SbString &	name,
		ParamValueType	val
	)			[inline]

UniformParamType is the type of parameter to set.

This function also generates the following helper methods not visible in the documentation:

• void setShaderParameter{1,2,3,4}i(const SbString&, ParamValueType)
• void setShaderParameter{1,2,3,4}f(const SbString&, ParamValueType)
• void setShaderParameterArray{1,2,3,4}i(const SbString&, ParamValueType)
• void setShaderParameterArray{1,2,3,4}f(const SbString&, ParamValueType)
• void setShaderParameterParameterMatrix

These are template methods, so ParamValueType must have an operator= compatible with the field value of the corresponding SoShaderParameter (for example, setShaderParameter2f can take an SbVec2f as ParamValueType).

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Friends And Related Function Documentation

friend class SoShaderProgram [friend]

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Member Data Documentation

SoSFBool SoShaderObject::isActive

Specifies if the shader object is active or not.

SoMFUniformShaderParameter SoShaderObject::parameter

Contains the shader's uniform parameters.

SoSFFilePathString SoShaderObject::sourceProgram

Contains the shader object's source program, specified by a filename (sourceType set to FILENAME) or by the string containing the program (sourceType set to ARB_PROGRAM, CG_PROGRAM, or GLSL_PROGRAM).

If the filename is not an absolute path name, the list of directories maintained by SoInput is searched. If the source program is not found in any of those directories, then the file is searched for relative to the directory from which the SoShaderObject node was read.

NOTE: The source type (sourceType) must be specified before the source program is specified.

SoSFEnum SoShaderObject::sourceType

Specifies the shader object's source type.

The type of source can be either a filename containing the program (FILENAME), or a string containing the source program (ARB_PROGRAM, CG_PROGRAM, or GLSL_PROGRAM). Use enum SourceType. Defaule is FILENAME.

NOTE: The source type must be specified before the source program (sourceProgram) is specified.

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The documentation for this class was generated from the following file:

• Inventor/nodes/SoShaderObject.h