在 2019年1月4日星期五 UTC+8下午12:46:39，徐一雄写道：
>
> Hello everyone, i'm a newbee to maya python API.
> Recently, I'm struggle in the single ray tracer.
> I build a custom MPxNode to compute the hitPoint when the ray hit the
> sphere.
> The ray is build by 2 locators in space.
> If the sphere is at the origin point of the world space, everything seems
> OK.
> But here is the* problem*:
> When I transform the sphere object, e.x translate a little distance. The
> hitPoint should translate on the sphere but now it doesn't .
> I know that when I transform the sphere, the input values of the custom
> node have't change and compute function doesn't be called.
> I have tried that to add a transform attribute to call the compute
> function but it doesn't work. I think the hitPoint should be calculate by
> multiply a matrix.
> So how can I achieve that when I transform the sphere, the hit point on
> the sphere also change by the direction of the ray.
> Thank you very much.
>
> Here is the *code*:
>
> import maya.OpenMaya as om
> import maya.OpenMayaMPx as ompx
>
> nodeName = 'RayTracer'
> nodeID = om.MTypeId(0X100fff)
>
>
> class MeshIntersectionNode(ompx.MPxNode):
> # Class Attrs
> # INPUT
> Loc_1_Pos = om.MObject()
> Loc_2_Pos = om.MObject()
>
> inMesh = om.MObject()
>
> # OUTPUT
> Loc_3_Pos = om.MObject()
>
> def __init__(self):
> ompx.MPxNode.__init__(self)
>
> def compute(self, plug, dataBlock):
> if plug != MeshIntersectionNode.Loc_3_Pos:
> return om.kUnknownParameter
>
> locator1Vector =
> om.MVector(dataBlock.inputValue(MeshIntersectionNode.Loc_1_Pos).asFloatVector())
> locator2Vector =
> om.MVector(dataBlock.inputValue(MeshIntersectionNode.Loc_2_Pos).asFloatVector())
> inputMeshObj =
> dataBlock.inputValue(MeshIntersectionNode.inMesh).asMesh()
>
> direction = om.MFloatVector(locator2Vector - locator1Vector)
>
> sourcePoint =
> om.MFloatPoint(dataBlock.inputValue(MeshIntersectionNode.Loc_1_Pos).asFloatVector())
>
> inputMeshMFn = om.MFnMesh(inputMeshObj)
>
> hitPoints = om.MFloatPoint()
>
> tolerance = float(0.0)
>
> inputMeshMFn.closestIntersection(sourcePoint, direction, None, None,
> False, om.MSpace.kWorld,
> 10000.0, False, None, hitPoints,
> None, None, None, None, None, tolerance)
>
> outputPoint = dataBlock.outputValue(MeshIntersectionNode.Loc_3_Pos)
>
> if hitPoints[0]:
> outputVector = om.MFloatVector(hitPoints.x, hitPoints.y,
> hitPoints.z)
> else:
> outputVector = om.MFloatVector(0.0, 0.0, 0.0)
>
> outputPoint.setMFloatVector(outputVector)
>
> dataBlock.setClean(plug)
>
>
> def nodeCreator():
> return ompx.asMPxPtr(MeshIntersectionNode())
>
>
> def nodeInitializer():
> MFnNumericAttr = om.MFnNumericAttribute()
> MFnMeshAttribute = om.MFnTypedAttribute()
>
> # create attribute
> # input
> MeshIntersectionNode.Loc_1_Pos =
> MFnNumericAttr.createPoint('Locator1Position', 'Loc1Pos')
> MFnNumericAttr.setWritable(1)
> MFnNumericAttr.setKeyable(1)
> MeshIntersectionNode.addAttribute(MeshIntersectionNode.Loc_1_Pos)
>
> MeshIntersectionNode.Loc_2_Pos =
> MFnNumericAttr.createPoint('Locator2Position', 'Loc2Pos')
> MFnNumericAttr.setWritable(1)
> MFnNumericAttr.setKeyable(1)
> MeshIntersectionNode.addAttribute(MeshIntersectionNode.Loc_2_Pos)
>
> MeshIntersectionNode.inMesh = MFnMeshAttribute.create('inMesh', 'im',
> om.MFnData.kMesh)
> MFnMeshAttribute.setWritable(1)
> MFnMeshAttribute.setKeyable(1)
> MeshIntersectionNode.addAttribute(MeshIntersectionNode.inMesh)
>
> # output
> MeshIntersectionNode.Loc_3_Pos =
> MFnNumericAttr.createPoint('Locator3Position', 'Loc3Pos')
> MFnNumericAttr.setWritable(0)
> MFnNumericAttr.setReadable(1)
> MeshIntersectionNode.addAttribute(MeshIntersectionNode.Loc_3_Pos)
>
> # make influence
> MeshIntersectionNode.attributeAffects(MeshIntersectionNode.Loc_1_Pos,
> MeshIntersectionNode.Loc_3_Pos)
> MeshIntersectionNode.attributeAffects(MeshIntersectionNode.Loc_2_Pos,
> MeshIntersectionNode.Loc_3_Pos)
> MeshIntersectionNode.attributeAffects(MeshIntersectionNode.inMesh,
> MeshIntersectionNode.Loc_3_Pos)
>
>
> def initializePlugin(mObj):
> mPlugin = ompx.MFnPlugin(mObj, 'Yixiong Xu', '1.0')
>
> try:
> mPlugin.registerNode(nodeName, nodeID, nodeCreator, nodeInitializer)
> except:
> raise RuntimeError
> print 'Failed to register node.'
>
>
> def uninitializePlugin(mObj):
> mPlugin = ompx.MFnPlugin(mObj)
>
> try:
> mPlugin.deregisterNode(nodeID)
> except:
> raise RuntimeError
> print 'Failed to deregister node.'
>
>
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