[Sidefx-houdini-list] PC cache from Mantra into SOP space?

Peter Bowmar pbowmar at gmail.com
Sun Aug 17 10:45:49 EDT 2008


Hey Simon,

Yeah, the cam projection was a whole other issue :) I was hoping the
"otransform" function would be available in SOPs, so you could specify
object->"/obj/cam1" as a transform but alas no joy.

I originally tried transforming the dumped .pc into a "World" Null but
then I could never get it to read back into the pciterate() in the
correct space when Mantra needed to use it. However, in that case I
could load the .pc straight into a File SOP and it was correct
relative to the camera.

It's not a huge deal since currently I'm just wanting to load the .pc
back in to visualize things but it'd be nice if it was easier.

Cheers,

Peter B

2008/8/17 Simon Barrick <simon at primalpictures.com>:
>
> Hi Peter, you need the camera projection matrix which normalises everything, I can't remember ever seeing anything about whether you can get access to that in sop vops. You could use a transform vop and transform the 3 axis vectors from object to world and then build the matrix you need from them and invert it. But does transforming a vector into world space in sop context actually mean anything??
>
> Si
>
> -----Original Message-----
> From: sidefx-houdini-list-bounces at sidefx.com on behalf of Peter Bowmar
> Sent: Sun 17/08/2008 04:33
> To: sidefx-houdini-list at sidefx.com
> Subject: [Sidefx-houdini-list] PC cache from Mantra into SOP space?
>
> Hi,
>
> So, trying to load in a PC file written from a pcwrite() in mantra, into SOPs.
>
> It all works except it's in the wrong space :(
>
>
> I use a VOP SOP and use "optransform()" (sadly, I can find no equiv
> VOP, have to use Inline VOP) which gives me the Camera's transform.
> Taking the inverse of that and multiplying it by P makes things
> better, but not perfect.
>
> Of course, the .pc file was written after the Camera was moved to the
> world 0,0,0 so this is logical.
>
> Here's where my bad matrix knowledge trips me up: I know I need to
> munge the optransform() matrix to transform that transform into
> "Camera Space" (i.e. camera looking down Z at 0,0,0) but for the life
> of me I can't figure out how. Anyone? Mario? :)
>
> Cheers,
>
> Peter B
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