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Pivot at the bottom of an object

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Hej guys- I am looking for a way, to move the pivot of a "transform node" to the bottom of the of an animated! geometry.


What i tried:




It's working, but only in the first frame - since my object is moving the left - the pivot don't move with the sphere. 




Any ideas?


Best jack










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Posted (edited)

Write this into your pivot translate to get the minimum y position of the input geo:

bbox(opinputpath(".", 0), D_YMIN)

opinputpath(".", 0) gets the path of the first input of the current node. https://www.sidefx.com/docs/houdini/expressions/opinputpath.html

bbox() returns the bounding box info of a node, in this case we want to use "D_YMIN" to get the minimum y position. https://www.sidefx.com/docs/houdini/expressions/bbox.html


edit: forgot to add the centroid expressions for the x and z values, see Tomas' reply below

Edited by markingleukc

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what you are doing with your bbox(0, 1) in Y is just making sure that your pivot's Y coordinate has the same value as the bottom of the geo

however since your animation seems to be in XZ plane, Y doesn't change therefore pivot will not move

you can put following expressions to px | py | pz: centroid(0, 0) | bbox(0, 1) | centroid(0, 2)

to center pivot in XZ and move to bottom in Y 

Edited by anim

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