blackpixel
1. Pre-render the whole thing in low resolution, and low settings so it outputs the attribute you want to use as a mask.
Then project UVs from the camera back onto the geometry and use the rendering as a texture in a PointSOP / Wrangle.
hi and thank you for your response with some ideas. I am actually doing something like this. I am using a “tex()” expression in a Primitive SOP to read the colors of the texture directly onto the Primitives of the Grid. However the geometry of the primitive has to be so dense in order to read the colors accurately (I am using a screen recording and need to capture info from the recording/animated material as geometry based on colors, if that makes sense), but because it is so dense this method takes eons to cook. I have over 7000 frames of animated material/texture to read and process in a ROP output and it has taken over 24 hours so far and is only 60 percent done rendering. I am not even sure if the geometry in my ROP will work for what I would like. This is why I was hoping to magically convert the texture to point or prim colors easily.
Unfortunately I would also have to search deep for some tuts on how to use a Point Wrangle the way you describe with uv's. I have seen some of Rohan Dalvi's tuts and hope to be able to find more. Houdini is harder than it was before Attributes/VEX became the mainstay of workflows.