[Sidefx-houdini-list] screen space pscale?

eetu at undo.fi eetu at undo.fi
Wed Sep 24 16:29:36 EDT 2014

On 2014-09-24 20:47, Anderson, Charles X. -ND wrote:
> I need to be able to set pscale on some points so that they are always
> 1 pixel wide regardless of distance from camera.   I've tried using a
> distance from camera times 1/x resolution, but it's not quite what I
> want.   Maybe something shader based using the fliterstep function.
> Any ideas?    Any ideas on how to treat a pixel not falling exactly on
> a pixel row or column?   Shift it slightly perhaps?  Should be simple
> but I'm just blanking out on this one.  Any help is greatly
> appreciated.

One thing to remember is to change the pixel filter on your rop, the 
default gaussian will blur your particles no matter what.
"box 1 1" is better, but if you just want really harsh sampling for the 
pixels you could use e.g. "minmax min", make sure the particle size is 
clearly less than a pixel and up the pixel samples.
This way the pixel will lit up even if just one of the samples hits the 

If you want to go with the shifting you could maybe do a projection to 
view space, clamp to pixel centers and then reproject back to world 


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