Forums Technical Discussion Point Instance procedural and orient attibute

Point Instance procedural and orient attibute

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Kym Watts
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34 posts
Joined: 9月 2014
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Hello,

I having a ton of trouble getting my head around this, I have a python sop, that is creating my point cloud.
Im giving is a postition & scale, those work correctly, but the orient is not.

In the attribute spread sheet, i can see the 3 params for the orient, all have values.

I simplified the code to include some transforms, originally they are coming from some worldspace maya transforms, but to confirm i wasnt going crazy i took a few from the moana island data set.

C:/leaf.obj , is a leaf geometry, but i have tried with a grid that is scales to be a rectangle.

node = hou.pwd()
geo = node.geometry()


pivot = {0,0,0}
v3 = hou.Vector3 (1,0,0)
m = hou.Matrix4()

geo.addAttrib(hou.attribType.Point, "orient",v3)
geo.addAttrib(hou.attribType.Point, "pscale",1.0)
geo.addAttrib(hou.attribType.Point, "instancefile", "")
# some test ws xforms
transforms = [
        [
            0.9476891756057739, 
            -0.3092913031578064, 
            0.07889299094676971, 
            0.0, 
            -0.06873862445354462, 
            0.043607283383607864, 
            0.9966812133789062, 
            0.0, 
            -0.3117051422595978, 
            -0.9499669671058655, 
            0.02006589248776436, 
            0.0, 
            50.91556930541992, 
            113.11812591552734, 
            -17.59348487854004, 
            1.0
        ],
        [
            0.011039327830076218, 
            -0.2005908042192459, 
            0.7990818023681641, 
            0.0, 
            -0.4085596799850464, 
            0.6926376819610596, 
            0.17951379716396332, 
            0.0, 
            -0.7154367566108704, 
            -0.39863455295562744, 
            -0.09018410742282867, 
            0.0, 
            95.37860107421875, 
            94.6856689453125, 
            -21.098573684692383, 
            1.0
        ], 
        [
            -0.7893863320350647, 
            0.09577027708292007, 
            -0.10461504757404327, 
            0.0, 
            0.11940404027700424, 
            0.7679983973503113, 
            -0.1979062259197235, 
            0.0, 
            0.07654441148042679, 
            -0.2103620171546936, 
            -0.7701525092124939, 
            0.0, 
            178.22116088867188, 
            64.501220703125, 
            24.868995666503906, 
            1.0
        ], 
        [
            -0.16089898347854614, 
            0.0215655155479908, 
            -0.6914180517196655, 
            0.0, 
            0.16879704594612122, 
            0.6896406412124634, 
            -0.017770059406757355, 
            0.0, 
            0.6708438992500305, 
            -0.16835418343544006, 
            -0.16136221587657928, 
            0.0, 
            134.9632568359375, 
            138.3452911376953, 
            109.56019592285156, 
            1.0
        ], 
        [
            0.12487196922302246, 
            -0.0351731963455677, 
            -0.7897642850875854, 
            0.0, 
            0.36846989393234253, 
            0.709984540939331, 
            0.026640724390745163, 
            0.0, 
            0.6994245052337646, 
            -0.3677535653114319, 
            0.1269664615392685, 
            0.0, 
            82.2651596069336, 
            77.03775787353516, 
            112.33985137939453, 
            1.0
        ], 
        ]

for world_space in transforms:

    m4 = hou.Matrix4(world_space)
    
    point = geo.createPoint()
    if point != None:
        # get the point location
        point.setPosition(m4.extractTranslates('srt'))
        
        # get its orient
        point.setAttribValue("orient", m4.extractRotates('srt'))
        #print m4.extractRotates('srt') i can see that this is different
        
        # get the uniform scale
        point.setAttribValue("pscale", (sum(m4.extractScales('srt')))/3.0)
        # set the leaf file
        point.setAttribValue("instancefile", "C:/leaf.obj")


Once this executes, i can see my leaves, positioned and scaled in the scene view, but they have no rotation


If someone can point me in the right direction would be fantastic.

Cheers
Kym
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jsmack
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7850 posts
Joined: 9月 2011
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The orient attribute as created is one dimension short of a quaternion (vector4).
The values being passed are from extract rotates are three dimensional euler rotations (xyz) not four dimensional quaternion rotations (wxyz).
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Kym Watts
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34 posts
Joined: 9月 2014
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Hi jsmack,

So the changes i made to the above, based on your information look like:

geo.addAttrib(hou.attribType.Point, "orient",hou.Quaternion())

#per point

qu = hou.Quaternion()
qu.setToRotationMatrix(m4.extractRotationMatrix3())

point.setAttribValue("orient", qu)

This give me some rotations, which is good, ill have to go back to my larger data set to see if matches what is coming from maya.

**edit, confirmed this gives me the correct rotations im after, thanks for your help.

Cheers
kym
Edited by Kym Watts - 2020年6月11日 17:01:14
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