GLSL Shader

Category: Realtime > OpenGL

Shader Family: Realtime

Output: Realtime

Builds a complete program using the high-level OpenGL Shading Language (GLSL). Vertex and fragment shaders can be defined as one "entity" within a single GLSL Shader node. For general information about working with this shader, see Setting Up a Unified GLSL Program [Realtime Shaders].

Program

Build

Sets the build options for your GLSL program:

Disable the program.
Compile the program without executing it.
Compile and execute the program.

Debug messages

Enables debug messages. Compilation results are logged and available from the script editor's log window.

To open the script editor, click the script icon at the bottom of the Softimage interface.

GLSL Vertex Program and Fragment Program

Enter the code for your vertex shader and fragment shader in the appropriate text editor. You can also load one of the preset shaders available from the Presets tab.

The text editor supports text customization (font, color, size), syntax styling, folding (hiding blocks such as functions and subroutines), auto-completion and highlighting for keywords. You can also implement this text editor widget in your own plug-ins. For more information, see Text Editor Widget [SDK Guide].

Draw

You do not need to connect the GLSL Program node to a Draw node in the render tree because the draw operations are handled directly within the GLSL Program shader.

Blending

In RGBA mode, pixels can be drawn using a function (glBlendFunc) that blends the incoming (source) RGBA values with the RGBA values that are already in the frame buffer (the destination values). For more information, see How Blending Works.

Use Blending

Enable or disable blending. When enabled, the blend function defines the operation of blending.

BlendScr

The blend source factor (sfactor) specifies which method is used to scale the source color components.

Select one of the supported methods from the drop-down menu. Each method defines four scale factors, one each for red, green, blue, and alpha. All scale factors have range [0,1].

BlendDest

The blend destination factor (dfactor) specifies which method is used to scale the destination color components.

Select one of the supported methods from the drop-down menu. Each method defines four scale factors, one each for red, green, blue, and alpha. All scale factors have range [0,1].

Alpha Testing

Alpha testing (glAlphaFunc) discards fragments depending on the outcome of a comparison between an incoming fragment's alpha value and a constant reference value. The alpha test specifies the reference value and the comparison function. The comparison is performed only if alpha testing is enabled.

The alpha function and alpha reference specify the conditions under which the pixel is drawn. The incoming alpha value is compared to AlphaRef using the function specified by AlphaFunc. If the value passes the comparison, the incoming fragment is drawn if it also passes subsequent stencil and depth buffer tests. If the value fails the comparison, no change is made to the frame buffer at that pixel location.

Alpha testing operates on all pixel write operations, including those resulting from the scan conversion of points, lines, polygons, and bitmaps, and from pixel draw and copy operations. It does not affect screen clear operations.

NoteAlpha testing is performed only in RGBA mode.

Perform Alpha Testing

Enable or disable alpha testing.

AlphaFunc

Specifies the alpha comparison function (func).

Select one of the supported comparison functions from the drop-down menu. The functions are defined as follows:

¥GL_NEVER

Never passes.
GL_LESS

Passes if the incoming alpha value is less than the reference value.
GL_EQUAL

Passes if the incoming alpha value is equal to the reference value.
GL_LEQUAL

Passes if the incoming alpha value is less than or equal to the reference value.
GL_GREATER

Passes if the incoming alpha value is greater than the reference value.
GL_NOTEQUAL

Passes if the incoming alpha value is not equal to the reference value.
GL_GEQUAL

Passes if the incoming alpha value is greater than or equal to the reference value.
GL_ALWAYS

Always passes.

AlphaRef

Specifies the reference value (ref) that incoming alpha values are compared to. This value is clamped to the range [0,1], where 0 represents the lowest possible alpha value and 1 the highest possible value.

Particle Cloud

Use Point Sprites

Enables the use of OpenGL point sprites. Draws an arbitrary shape at each point position by means of a texture called a point sprite. If this shader is applied to a point cloud, it will render sprites instead of points.

Presets

Particle Cloud

Default Shader	A simple GLSL shader that transforms the incoming vertices by the current modelview matrix using the ftransform() function. This is equivalent to transforming the point using fixed-function.
Color + Size Shader	Renders a particle cloud as a set of colored points of varying sizes. Both Color and Size must be initialized attributes in your ICE tree. See Getting and Setting Data in ICE Trees [ICE Fundamentals].
Age Shader	Renders a particle cloud as points of varying size and color depending on age.
Velocity Shader	Renders a particle cloud as points of varying color dependant on each particle's velocity. This shader takes the PointVelocity ICE attribute and puts it in the normal register. Then, the vertex shader takes the length of the vector and puts it in a float value called l_fAbsVel (absolute velocity). It then uses that value to drive the red component of each particle.

Triangle Mesh

Point Light Shader	A vertex and fragment shader that implement a point light source.
Spot Light Shader	A vertex and fragment shader that implement a spotlight source.
Spherical Harmonics	A vertex and fragment shader that implement spherical harmonics lighting.

Advanced

Graphics hardware usually have a small number of fixed locations for passing standard and generic vertex attributes. Therefore, the OpenGL Shading Language defines each non-matrix attribute variable as having space for up to four floating-point values (a vec4). There is an implementation dependent limit on the number of attribute variables that can be used and if this is exceeded it will cause a link error. However, attribute variables that are declared but not used do not count against this limit. A float attribute counts the same amount against this limit as a vec4, so you may want to use attribute packing techniques such as grouping four unrelated float attributes together into a vec4 to better utilize the capabilities of the underlying hardware. Softimage's GLSL Program shader will ignore any matrix attributes that are mapped to a register.

Hardware Attribute Mapping

	Click and choose Set Default Polygon Mesh or Particle Cloud to set the default attribute mappings for a polygon mesh or a point cloud. Click and choose Clear All to empty the entire hardware attribute mapping table. You can then add your mapping entries from scratch.
	Refreshes the attributes and registers available in each list. Refreshing is particularly useful when you have made modifications to the polygon mesh or point cloud being read by the shader. Any new (or recently initialized) attributes are displayed in the attributes list. If a register is no longer assigned it will be added back to the registers list.
	Adds an attribute and register mapping (row) to the hardware attribute mapping table. To modify this mapping, first click the attribute entry and select an available attribute from the attributes list. Then click the corresponding register entry and select an available register from the registers list.
	Deletes the selected attribute and register mapping (row) from the hardware attribute mapping table.
Attribute	The Attribute column of the hardware attribute mapping table holds the attribute entries that each represent one of the 0D components that exist or can be created on the polygon mesh or point cloud.
Hardware Register	The Hardware Register column of the hardware attribute mapping table holds the register entries that each represent one of the possible register locations available on most OpenGL graphics accelerators.

Vertex Attributes Passed Using...	Type	Components	Hardware Register	Additional Information
gl_Color	vec4	r, g, b, a	color0	Typically used for vertex colors.
gl_SecondaryColor	vec4	r, g, b, a	color1	Typically used for vertex colors.
gl_Normal	vec3	x, y, z	normal	Typically used for normal coordinates.
gl_Vertex	vec4	x, y, z, w	position	Typically used for vertex coordinates.
gl_PointSize	float	x	psize	Typically used for point size (pixels).
gl_MultiTexCoord0	vec4	x, y, z, w	texcoord0	Typically used for texture coordinates.
gl_MultiTexCoord1	vec4	x, y, z, w	texcoord1	Typically used for texture coordinates.
gl_MultiTexCoord2	vec4	x, y, z, w	texcoord2	Typically used for texture coordinates.
gl_MultiTexCoord3	vec4	x, y, z, w	texcoord3	Typically used for texture coordinates.
gl_MultiTexCoord4	vec4	x, y, z, w	texcoord4	Typically used for texture coordinates.
gl_MultiTexCoord5	vec4	x, y, z, w	texcoord5	Typically used for texture coordinates.
gl_MultiTexCoord6	vec4	x, y, z, w	texcoord6	Typically used for texture coordinates.
gl_MultiTexCoord7	vec4	x, y, z, w	texcoord7	Typically used for texture coordinates.
gl_FogCoord	float	x	fogcoord	Typically used for fog coordinates.
glVertexAttrib	short, float, int, double, unsigned byte, unsigned short, unsigned int	x, y, z, w	attr[0...15]	Softimage's GLSL shader does not support the passing of generic vertex attribute values to attr hardware registers. If you are using the glVertexAttrib family of entry points to pass generic vertex attributes into numbered locations, you will have to write your own application code (shader objects) to be able to take advantage of the attr hardware resgisters.
glMultiTexCoord[6]	vec4	x, y, z, w	tangent	OpenGL does not have a defined vertex attribute for a tangent vector. You can assign it to the tangent register which is aliased to the texcoord6 register. Softimage encodes tangents into a 4-float rgba vertex color.
glMultiTexCoord[7]	vec4	x, y, z, w	binormal	OpenGL does not have a defined vertex attribute for a binormal vector. You can assign it to the binormal register which is aliased to the texcoord7 register. Softimage encodes binormals into a 4-float rgba vertex color.
D3DDECLUSAGE_BLENDWEIGHT		x, y, z, w	weight	Softimage's GLSL Program shader does not support the passing of values to these registers. However, these registers are made available in anticipation that shader developers will rewrite this shader implementation to take advantage of DirectX-based GPU skinning features.
D3DDECLUSAGE_BLENDINDICES		x, y, z, w	indice
D3DDECLUSAGE_SAMPLE		x, y, z, w	sample
D3DDECLUSAGE_TESSFACTOR		x	tessfactor
D3DDECLUSAGE_DEPTH		x	depth