Work with CgFX shaders

Adding placement into CgFx shaders

Cgfx shaders do not automatically support texture placement which is found inside Maya (place2DTexture or place3DTexture node) because CgFx is a node which uses a programmable shading language. Using this language means that the texture transform cannot be set from outside. Instead, it needs to be explicitly coded into the shader. If such parameters are in the shader, then the automatic UI generation creates the UI elements. You should then connect the appropriate attributes from the texture placement node(s) to the attributes on the shader.

Reloading, Editing and Viewing CgFx files

In the Attribute Editor of the cgfxShader node, you can use the Reload, Edit and Open buttons to work on the FX file you’ve specified.

Reload

Reloads the specified CgFx file from the disk.

Edit

Opens the specified CgFx file in Microsoft^® Notepad on Windows, and vi on Linux, for editing. Edit the file as required, and save it. Maya automatically reloads the CgFx file.

Open

Opens the specified CgFx file in Notepad in read-only format on Windows, and vi on Linux.

Orientation for the texture co-ordinate system

Beginning Maya 2012, when the CgFX plug-in compiles a CgFX shader, it sets either the compilation macro MAYA_TEXCOORD_ORIENTATION_OPENGL or MAYA_TEXCOORD_ORIENTATION_DIRECTX to 1 to specify the orientation used for the texture co-ordinate system.

Set the MAYA_TEXCOORD_ORIENTATION environment variable to either OPENGL or DIRECTX to define the MAYA_TEXCOORD_ORIENTATION_OPENGL or MAYA_TEXCOORD_ORIENTATION_DIRECTX macros respectively. When the macro is defined, it is set to 1.

OPENGL

Specifies that the OpenGL convention is used, where the origin of the texture is at the bottom-left corner of the texture.

DIRECTX

Specifies that the DirectX convention is used, where the origin of the texture is at the top-left corner of the texture.

For Maya 2011 and below, both macros are undefined and the shader should assume a DirectX texture co-ordinate orientation.

For Maya 2014/2013/2012, by default, the MAYA_TEXCOORD_ORIENTATION_OPENGL macro is set to 1. You can change this by setting the environment variable MAYA_TEXCOORD_ORIENTATION to DIRECTX before starting Maya.

Setting the MAYA_TEXCOORD_ORIENTATION environment variable to DIRECTX may be useful when using the Default renderer or the Hardware renderer along with shaders that have been written for previous versions of Maya and that have not been modified to support the OPENGL texture coordinate orientation. When the MAYA_TEXCOORD_ORIENTATION environment variable is set to DIRECTX in Maya 2014/2013/2012, the following occurs:

• The shader will be compiled with the MAYA_TEXCOORD_ORIENTATION_DIRECTX macro set to 1.
• The texture will be loaded using the DirectX orientation.
• The Default renderer and Hardware renderer will generate UV coordinates using the DirectX orientation.

  However, there is a limitation that causes the Viewport 2.0 to still generate UV coordinates using the OpenGL orientation. This may cause the textures to be rendered flipped along the V-axis when the Viewport 2.0 is used.

This changes both the generation of the UV co-ordinates and the loading of the texture image such that if a shader uses UV coordinates to sample a texture, then the rendered image will be the same in both coordinate systems. However, when UVs procedurally generated by the shader (as opposed to ones coming from a UV source stream generated by Maya) are used to sample a texture, the plug-in must be able to handle both conventions. The brix.cgfx example included in $(MAYA_ROOT)/presets/CgFX/example provides an example of how this should be done:

/******************** pixel shader *********************/
#ifdef MAYA_TEXCOORD_ORIENTATION_OPENGL
     float GBalanceCorr = 1.0f - GBalance;
 #else     
     float GBalanceCorr = GBalance;
#endif
    
    float v = ((float4)tex2D(stripeSampler,float2(IN.BrickUV.x,0.5))).x;
    float4 dColor1 = lerp(SurfColor1,SurfColor2,v);
    v = ((float4)tex2D(stripeSampler,float2(IN.BrickUV.x*2,GBalanceCorr))).x;   
    dColor1 = lerp(GroutColor,dColor1,v);
    v = ((float4)tex2D(stripeSampler,float2(IN.BrickUV.x+0.25,0.5))).x;  
    float4 dColor2 = lerp(SurfColor1,SurfColor2,v);
    v = ((float4)tex2D(stripeSampler,float2((IN.BrickUV.x+0.25)*2,GBalanceCorr))).x;
    dColor2 = lerp(GroutColor,dColor2,v);
    v = ((float4)tex2D(stripeSampler,float2(IN.BrickUV.y,0.5))).x;
    float4 brix = lerp(dColor1,dColor2,v);
    v = ((float4)tex2D(stripeSampler,float2(IN.BrickUV.y*2,GBalanceCorr))).x;  
    brix = lerp(GroutColor,brix,v);
       return IN.DCol * brix;
}

Customizing the CgFX shader

You can use the MAYA_CGFX macro to customize your CgFX shaders to include Maya specific attribute annotations without breaking the compatibility with other applications that might also use the same CgFX shader.

For example, you can use the following code to declare the directional light attribute in both Maya and another application without causing any compatibility issues:

#if defined(MAYA_CGFX) || defined(XSI)
// Declares the « dirlight0 » with attribute annotations for Maya or XSI
float4 dirlight0 : Direction <
     string UIName =  "Distant Light 0 Direction";
     string Object = "DirectionalLight";
     string Space = "World";
> = {-1.0f, -1.0f, 0.3f, 0.0f};
#else
// Declares the « dirlight0 » with attribute annotations for another application:
....
#endif

The lines between #if defined(MAYA_CGFX) || defined(XSI) and #else are only parsed when loaded by Maya/XSI.