...

The RIX_PATTERNCREATE() method is called by the renderer to create an instance of the pattern plugin. Generally, the implementation of this method should simply return a new allocated copy of your pattern class. Similarly, the R IX_PATTERNDESTROY() method is called by the renderer to delete an instance of the pattern plugin; a typical implementation of this method is to delete the passed in pattern pointer:

  
    RIX_PATTERNCREATE
    {
        return new MyPattern();
    }

...

    // Find the number of outputs

    RixSCParamInfo const* paramTable = GetParamTable();

    int numOutputs = -1;

    while (paramTable[++numOutputs].access == k_RixSCOutput) {}

    // Allocate and bind our outputs

    RixShadingContext::Allocator pool(sctx);

    OutputSpec* out = pool.AllocForPattern<OutputSpec>(numOutputs);

    *outputs = out;

    *noutputs = numOutputs;
    
    // looping through the different output ids

    for (int i = 0; i < numOutputs; ++i)

    {
        out[i].paramId = i;

        out[i].detail = k_RixSCInvalidDetail;

        out[i].value = NULL;
        type = paramTable[i].type; // we know this

     

        sctx->GetParamInfo(i, &type, &cinfo);

        if(cinfo == k_RixSCNetworkValue)

        {
            if( type == k_RixSCColor )

            {

                out[i].detail = k_RixSCVarying;

                out[i].value = pool.AllocForPattern<RtColorRGB>(sctx->numPts);

            }

            else if( type == k_RixSCFloat )

            {

                out[i].detail = k_RixSCVarying;

                out[i].value = pool.AllocForPattern<RtFloat>(sctx->numPts);

            }

        }

    }
  

Finally, the pattern can now actually compute the values that go into the output buffers. This is typically done by using the inputs and looping through the number of shaded points RixShadingContext::numPts to compute some values that are stored in the allocated output buffers.

for (int i=0; i<sctx->numPts; i++)
{
    // Compute some output values based on your input. Here we assume
    // outColor is the memory buffer allocated for an output parameter,
    // and inputColor and inputFloat are two inputs that were returned from
    // EvalParam.
    if (style == 1)
    {
        outColor[i] = inputColor[i] * inputFloat[i];
    }
}

...

Display "patternTest" "framebuffer" "rgba"
Quantize "rgba" 255 0 255 0
Format 128 128 1
Projection "perspective" "fov" [45]
Hider "raytrace" "string integrationmode" ["path"]
Integrator "PxrPathTracer" "integrator"

WorldBegin

    AttributeBegin
        Attribute "identifier" "name" ["sphere1"]
        Translate 0 0 2.75

        Pattern "PxrCustomPattern" "customPattern"

        Bxdf "PxrDiffuse" "smooth"
            "reference color diffuseColor" "customPattern:outColor"
        Sphere 1.0 -1.0 1.0 360.0
    AttributeEnd

WorldEnd

Creating a Pattern args File

...