maya api - MFnMesh::allIntersections, too slow

[s...@weacceptyou.com]

Hello all,

im kind of stupid when it comes to using the api, but i needed it to check for intersections in my mesh when firing rays out from a particular point. In my script i need to be firing a hell load of rays. Probably around 500 by the end.

my program currently takes 23 seconds to process, and i have only finished about 10% of its full size in the end. About 16 seconds is taken up with the firing of the rays. It takes 0.04 seconds roughly to fire each ray. Which adds up quikly.

Does anyone know a clever way of streamlining the mFnMesh allIntersections thingy, maybe an alternative method. I just need to have something that takes a position and a vector and returns the coords of the interesection,

any help would be great,
Thanks,
Sam

[e955...@gmail.com]

by the way here is a snippet of my code, the mesh.allIntersections thing is the part that is taking too long:

def returnCollisionPoints(self, point, dir):


sel = om.MSelectionList()
dag = om.MDagPath()

sel.add("BASE_MESHShape")
sel.getDagPath(0,dag)

mesh = om.MFnMesh(dag)

point = om.MFloatPoint(*point)
dir = om.MFloatVector(*dir)
hitPoints = om.MFloatPointArray()

mesh.allIntersections(
point, dir,
None, None,
False, om.MSpace.kWorld,
10000, False,
None,
True,
hitPoints,
None, None,
None, None,
None
)

return hitPoints

[e955...@gmail.com]

ok apparently a mesh look up accelerator is needed to speed up the raytracing. God knows how to implement it though....

[Janos Hunyadi]

mesh.allIntersections( 

                                point, dir, 
                                None, None, 
                                False, om.MSpace.kWorld, 
                                10000, False, 
                                None, 
                                True, 
                                hitPoints, 
                                None, None, 
                                None, None, 
                                None 
                        )      

just replace NONE with inMesh.autoUniformGridParams()

According to the maya API docs:

static MMeshIsectAccelParams	uniformGridParams (int xDiv, int yDiv, int zDiv)
	Creates a MMeshIsectAccelParams configuration object to pass to the methods MFnMesh::closestIntersection(), MFnMesh::anyIntersection(), or MFnMesh::allIntersections().
static MMeshIsectAccelParams	autoUniformGridParams ()
	Creates a MMeshIsectAccelParams configuration object to pass to the methods MFnMesh::closestIntersection(), MFnMesh::anyIntersection(), or MFnMesh::allIntersections().

[Janos Hunyadi]

in your case inmesh.autoUniformGridParams(),  being mesh.autoUniformGridParams()

[e955...@gmail.com]

thankyou very much Janos, alot of this api stuff is slowly starting to make sense to me.

cheers,
Sam