[Sidefx-houdini-list] Confused about ptransform(), wo_space(), ow_space() and rest position.

Mark Elendt mark at sidefx.com
Fri Aug 13 09:47:10 EDT 2010


The wo_space() etc. functions existed before the general transform()
function.  The "world" space which these functions refer to was in
fact "camera" space.  Prior to the general transform() function, there
was no way to get to actual "world" space.

The wo_space() functions are hold-overs and their use should really be
deprecated.

On Friday Aug 13 at 15:14, Vinz wrote:
> Hi,
> 
> I'm a bit confused about spaces transforms in a vop surface.
> 
> First I tried the transform vop, which uses the ptransform() function.
> This one works as expected, from what I understand, in a vop surface, 
> the current space is camera space, and if I transform the P in the vop 
> from camera space to object space I get the expected result (same P as 
> in SOP).
> 
> 
> Then I noticed that the rest position node, when no attribute rest 
> exists, uses a uvspace change which itself corresponds to 
> wo_space()/wt_space()/toNDC().
> 
> The wo_space() and wt_space() function give me the same result, which is 
> the same as ptransform("space:camera", "space:object").
> And this is what I don't understand at all.
> 
> The help says for wo_space() : transforms a position value from World to 
> Object space.
> for wt_space() : transforms a position value from World to Texture space.
> 
> What's the difference between these two ? And it looks like they 
> transform from camera to object space and not from world to 
> object/texture space.
> 
> 
> Thanks a lot for clearing things up,
> Vincent
> 
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-- 
Mark Elendt



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