Camera XY Pos of Points at SOP level

[Annon]

Hey all,

I need to save the XY pos in camera space of some points at SOP level.

So from left to right will be 0-1, bottom to top 0-1 of the point in camera space saved as a point attribute.

I would have thought it could have been done with a transform in VOPSOPs, but I'm not sure exactly of the syntax to use, if indeed it works at all.

Any ideas?

Thanks

Christian

P.s. I've attached a simple scene to show you what I mean.

cameraXYSOP.hip

[eetu]

I've had no luck with the Transform VOP in a SOP context

You're in luck though, there is a "Perspective From Camera" projection type in the UVTexture SOP

[anim]

you can use toNDC VOP to convert P to screen space coords

[jkunz07]

I got the green (y) component to work but the red (x) and blue (z) need to have something done to them, not sure what at the moment...

EDIT: This is pretty much it, the x values seem a little odd, you probably have to remap x and y to your aspect ratio as the coordinates appear to be in more of a 1:1 ratio currently.

cameraXYSOP_almost.hipnc

Edited May 19, 2012 by jkunz07

[anim]

this is what I meant by toNDC VOP

while it is computing Z component as a distance from the camera which can be useful, you can easily discard that information to get just XY

cameraXYSOP_fix.hip