Found a workaround, making my own orient constraints with matrices instead,
but I wouldn't mind some explanation on this, because I'm still not sure
why the scale has so much impact on an orient constraint
Le mardi 13 août 2019 17:38:36 UTC-4, vince touache a écrit :
>
> Hi,
>
> I noticed a weird behavior when trying to scale a constraint object.
> My setup is made of 3 elements. One parent and its child, and a null, at
> the same level as parent. parent and null are aimConstraining the child (so
> the child will follow .5 each)
> parent
> |__ child
> null
>
> The weirdness happens when combining rotation and scale, which introduces
> some shear effect.. what I can't figure out though, is why this shear is
> affecting so much the rotation (my vectors are still visible as
> perpendicular).
>
> To check by yourself, you can run this snippet :
>
> parent = cmds.createNode('transform', ss=1)
> cube = cmds.polyCube()[0]
> cmds.parent(cube, parent, r=1)
> null = cmds.createNode('transform', ss=1)
> cmds.orientConstraint(parent, null, cube, mo=0)
> cmds.setAttr(parent + '.rx', 45)
> print 'before scale / shear', cmds.getAttr(cube + '.rx')
> cmds.setAttr(parent + '.sy', 2)
> print 'after scale / shear', cmds.getAttr(cube + '.rx')
>
>
> Before scaling, the rotateX of my cube is correct, but after, it's like
> 40-is degrees, which doesn't make much sense to me....
> I have a shitty fix (run this code)
> # shittyFix
> dcm = cmds.createNode('decomposeMatrix', ss=1)
> cmds.connectAttr(cube + '.wm', dcm + '.inputMatrix')
> cpm = cmds.createNode('composeMatrix', ss=1)
> cmds.connectAttr(dcm + '.or', cpm + '.ir')
> cmds.connectAttr(dcm + '.os', cpm + '.is')
> cmds.connectAttr(dcm + '.ot', cpm + '.it')
> outDcm = cmds.createNode('decomposeMatrix', ss=1)
> cmds.connectAttr(cpm + '.outputMatrix', outDcm + '.inputMatrix')
> outLoc = cmds.spaceLocator()[0]
> cmds.connectAttr(outDcm + '.orx', outLoc + '.rx')
> print 'after shitty fix', cmds.getAttr(outLoc + '.rx')
>
> but it's still not perfect, and I'm not sur why... could this be due to
> some round issue ? That looks too much to me...
> Does anyone have an idea on how to get my proper pCube.rx = 22.5, with
> this setup (i.e. compensate the shear) ??
>
> Thanks a lot !
>
>
>
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