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C++ API Reference
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C++ API Reference
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Base class for user defined GPU deformer override evaluators. More...
#include <MPxGPUDeformer.h>
Public Member Functions | |
| MPxGPUDeformer () | |
| Constructs an MPxGPUDeformer. | |
| virtual | ~MPxGPUDeformer () |
| Destructor. | |
| virtual DeformerStatus | evaluate (MDataBlock &block, const MEvaluationNode &evaluationNode, const MPlug &outputPlug, unsigned int numElements, const MAutoCLMem, const MAutoCLEvent, MAutoCLMem, MAutoCLEvent &) |
| This method is deprecated and should no longer be used. More... | |
| virtual DeformerStatus | evaluate (MDataBlock &block, const MEvaluationNode &evaluationNode, const MPlug &outputPlug, const MGPUDeformerData &inputData, MGPUDeformerData &outputData) |
| evaluate() is called each time the deformation chain is evaluated. More... | |
| virtual void | terminate () |
| This method is called when the GPU deformer is being destroyed. More... | |
| MGPUDeformerBuffer | createOutputBuffer (const MGPUDeformerBuffer &inputBuffer) |
| This method creates an output buffer based on inputBuffer. More... | |
| bool | getIndexMapper (MIndexMapper &imap) |
| This method update if required the IndexMapper information. More... | |
Static Public Member Functions | |
| static bool | hasAttributeBeenModified (const MEvaluationNode &evaluationNode, const MObject &attribute) |
| This method returns true if the data for attribute on the overridden deformation node has been modified since the last call to MPxGPUDeformer::evaluate(). More... | |
| static MUniqueString | sPositionsName () |
| static MUniqueString | sGeometryMatrixName () |
| static MUniqueString | sInverseGeometryMatrixName () |
Base class for user defined GPU deformer override evaluators.
MPxGPUDeformer lets you create user-defined GPU deformer overrides. A GPU deformer override replaces the CPU implementation of a deformer node when the evaluation manager is enabled and the deformerEvaluator plug-in is enabled. Use MPxGPUDeformer to override the deformation for a Maya deformer or for a plug-in deformer implemented through MPxDeformerNode. MPxGPUDeformer must register which node type it overrides using MGPUDeformerRegistry.
MPxGPUDeformer defines a deformer node as a node which has input geometry and output geometry. MPxGPUDeformer assumes that the number of vertices in the input and output geometry of a deformer node are the same. This definition includes nodes which are traditionally thought of as deformer nodes, such as skinCluster or blendShape, but also includes nodes like groupParts, which may be part of deformation chains.
To ensure optimal performance when you implement MPxGPUDeformer, keep the following in mind:
If you use this interface, you must implement the virtual method evaluate() for MPxGPUDeformer to function. See the evaluate() documentation for additional requirements on the evaluate() method. The terminate() method is optional.
About the deformer evaluator:
The deformer evaluator identifies chains of supported nodes terminated by a mesh. The deformer evaluator then replaces CPU evaluation of these nodes with GPGPU kernels. The final deformed geometry is directly shared with Viewport 2.0, which avoids any GPU read back. When you implement an MPxGPUDeformer for a given node type, you expand the list of deformer evaluator supported nodes, which then allows more deformer chains to execute on the GPU.
A deformer chain is created by identifying an animated display mesh and then following geometry connections upstream until a source plug, that meets any one of the following criteria, is reached:
When one of the preceding conditions is true for a source plug, that source plug is considered the input to the deformation chain, and the corresponding source plug node is not evaluated in the deformer evaluator.
Example Chains:
Example 1:
When the deformer evaluator initializes it identifies HistoryNode2.outputData as the source plug. The first time that the deformer evaluator runs on example 1, the HistoryNode2 geometry output is copied to the GPU. SupportedNode1 and SupportedNode2 then run kernels to perform the deformations, and the final deformed result is then shared with VP2. Subsequent evaluations re-use the copy of HistoryNode2 output geometry already on the GPU, which avoids expensive data transfer.
Example 2:
In this scenario, UnsupportedNode1 runs on the CPU and generates an intermediate result. This intermediate result is copied to the GPU. Once copied, SupportedNode1 runs its kernel and displayMesh shares data with VP2. The intermediate result is copied to the GPU every frame, resulting in slower performance.
Example 3:
In this scenario, the deformer evaluator does nothing. If we performed SupportedNode1's deformation on the GPU, we would need to read back that data and use it as an input for UnsupportedNode1 on the CPU. Read back is not supported by the deformer evaluator.
Example 4:
In this scenario, the deformer evaluator creates two chains, one for displayMesh1 and a second for displayMesh2. These chains both run on the GPU. Note that if SupportedNode1 is derived from MPxDeformerNode, then there can be zero relationship between the mesh data used in displayMesh1 and displayMesh2. displayMesh1 could have 100 vertices, and displayMesh2 could have one million vertices.
Example 5:
In this scenario, the deformer evaluator does nothing. We do support the first chain for displayMesh1, but we do not support the chain for displayMesh2. The deformer evaluator does not support the partial override of a node. In this case, SupportedNode1 has only partial support because the deformer evaluator can override evaluation for outMesh[0] but not for outMesh[1]. This prevents deformer evaluator from doing any GPU work in this scenario.
The deformer evaluator allocates a unique MPxGPUDeformer object for each supported node in each supported chain. In Example 4, two MPxGPUDeformer objects are allocated for SupportedNode1, one for multi-element 0 and a second for multi-element 1.
The deformer evaluator's emphasis on avoiding geometry read back from the GPU means that unsupported nodes that follow a deformation chain exclude that chain from GPU evaluation.
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This method is deprecated and should no longer be used.
Instead use MPxGPUDeformer::evaluate(MdataBlock&, const MEvaluationNode&, const MPlug&, const MGPUDeformerData&, MGPUDeformerData&). The provided implementation of this function returns kDeformerFailure. Derived classes should only implement one version of the evaluate function.
| [in] | block | The data block of the deformer node to be overridden. |
| [in] | evaluationNode | The evaluation node of the deformer to be overridden. |
| [in] | outputPlug | The output plug of the deformer to be overridden. |
| [in] | numElements | The number of float3 elements in inputPositionBuffer and outputPositionBuffer. |
| [in] | inputPositionBuffer | The handle to the input positions on the GPU. |
| [in] | inputEvent | The event that must be completed before it is safe to read values in inputPositionBuffer. |
| [in] | outputPositionBuffer | The handle of the output positions on the GPU. |
| [out] | outputEvent | The event which must be completed before it is safe to read outputPositionBuffer. |
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evaluate() is called each time the deformation chain is evaluated.
evaluate() is given an input MGPUDeformerData and an output MGPUDeformerData. The input MGPUDeformerData holds one or more named MGPUDeformerBuffer objects which represent the input data for the deformer.
evaluate() should enqueue kernels to perform the deformation. Each kernel must:
It is safe to enqueue multiple kernels from evaluate(). It is safe to read values from the data block and evaluation node passed into evaluate(). It is not necessarily fast to read values from the data block. Reading the value of MPxGeometryFilter::inputGeom or MPxGeometryFilter::outputGeom may caused unexpected CPU evaluation to occur. This evaluation is safe but slow. It is safe to read values for the deformation node being overridden by creating MPlug objects to read values. It is not safe to access data on any other node or data structure during evaluate(). evaluate() may be invoked in parallel with other dependency graph evaluation or calls to evaluate() for other deformer nodes. Any output buffer written to by evaluate() must be added to outputData. Any input buffer not written to by evaluate() will automatically appear as an input to the next downstream deformer. Any buffer in outputData will automatically appear as an input to the next downstream deformer.
If an implementation of evaluate() must be executed with access to the D3D / GL context because of some GPGPU to D3D / GL interop, then evaluate() returns kDeformerRetryMainThread. evaluate() is called a second time for that frame; this call is guaranteed to have safe access to the GPU context.
MGPUDeformerData inputData contains several MGPUDeformerBuffer objects created by deformer evaluator:
Input vertex positions is a cl_mem object that stores the input mesh positions as float3 elements. Input vertex positions is readable but may or may not be writable. The vertices stored in input vertex positions are stored in the same order that MItGeometry visits the vertices. It is not safe to read input vertex positions until the buffer ready event in the input MGPUDeformerBuffer is complete.
Geometry matrix stores the geometry matrix as 16 float values in row major order.
Inverse geometry matrix stores the inverse geometry matrix as 16 float values in row major order.
This is the same order convention as other matrices in Maya, represented as MMatrix.
The MGPUDeformerBuffers in inputData may be read-only or read-write. evaluate() must create a new MGPUDeformerBuffer object to be used as the output. This MGPUDeformerBuffer can be safely created on the stack, it will be copied when it is added to outputData.
The output MGPUDeformerBuffer must have the same name as the input buffer and be backed by GPU storage large enough to hold the deformer output. createOutputBuffer() will automatically create an output buffer which is appropriate to use in most cases. It is not safe to hold any reference to a cl_mem object returned by createOutputBuffer() after the end of evaluate(). createOutputBuffer() never creates an MGPUDeformerBuffer which is read only.
Each output buffer must be added to outputData for that data to be available to downstream deformers. When a buffer is added to outputData its values are copied and stored in a separate structure, any further modification to the members of the buffer will not be reflected in the buffer in outputData.
If the evaluate() function returns kDeformerSuccess then outputData must contain at least a position buffer. Additional output buffers are optional.
If the evaluate() function returns kDeformerPassThrough then outputData must not contain a position buffers. Additional output buffers are optional.
The provided implementation of MPxGPUDeformer::evaluate(MdataBlock&, const MEvaluationNode&, const MPlug&, const MGPUDeformerData&, MGPUDeformerData&) calls the deprecated version of this function evaluate(MDataBlock&, const MEvaluationNode&, const MPlug&, unsigned int, const MAutoCLMem, const MAutoCLEvent, MAutoCLMem, MAutoCLEvent&) for backwards compatibility.
Derived classes should only implement one version of the evaluate function.
| [in] | block | The data block of the deformer node to be overridden. |
| [in] | evaluationNode | The evaluation node of the deformer to be overridden. |
| [in] | outputPlug | The output plug of the deformer to be overridden. |
| [in] | inputData | The input data for this deformer, including geometry. |
| [in] | outputData | The output data for this deformer, including geometry. |
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This method is called when the GPU deformer is being destroyed.
Any data stored on this object should be released.
| MGPUDeformerBuffer createOutputBuffer | ( | const MGPUDeformerBuffer & | inputBuffer | ) |
This method creates an output buffer based on inputBuffer.
If inputBuffer is read only then the returned MGPUDeformerBuffer will be backed by a different cl_mem object large enough to hold the data stored in inputBuffer. If inputBuffer is writable then the returned MGPUDeformerBuffer is backed by the same cl_mem as inputBuffer. The MGPUDeformerBuffer returned by createOutputBuffer() is never read only.
It is not safe to hold the MGPUDeformerBuffer returned by createOutputBuffer after the end of the evaluate() call. It is not safe to hold a reference to the cl_mem underlying an MGPUDeformerBuffer after the end of the evaluate() call.
createOutputBuffer uses a pool of cl_mem objects to fulfill requests for output buffers. This avoids allocating a new writable cl_mem object each time the deformation chain is evaluated.
| [in] | inputBuffer | The input version of the buffer we would like to create an output buffer for. |
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This method returns true if the data for attribute on the overridden deformation node has been modified since the last call to MPxGPUDeformer::evaluate().
hasAttributeBeenModified returning true may indicate that the attribute is animated or that the attribute has been interactively changed.
| [in] | evaluationNode | The evaluation node of the deformer which is overridden. |
| [in] | attribute | The attribute to test. |
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| bool getIndexMapper | ( | MIndexMapper & | imap | ) |
This method update if required the IndexMapper information.
To be uses when implementing GPU deformation. It uses information on the deformer and compute the indices that are meant to be deformed. This is meant to be called every evaluation and refresh the GPU buffers only if it return true.
| [in] | imap | The IndexMapper to be filled only if out of date |
1.8.10 
