OK I've been trying to do a tutorial and then do it again my own way to make sure I'm understanding it. I've watched the applied houdini particles 1, and the entagma particles tutorial where they emit particles using the point color. The problem is that both of them do it by using a high res model or subdividing it to get high res. Is there a way to get it to work on a lower resolution model and scattering points on it like I have in my attachment? It looks like Houdini only allows the emission attribute if you use the “scatter on surface” in the Pop source. The problem is that then it inherits a low resolution version of the color attribute.

SOLVED near end of thread using an Point Wrangle
if(luminance(@Cd) < chf('cutoff')) removepoint(geoself(),@ptnum);

You can increase the amount of points that get scattered in the scatter node.

The problem is that in the PopNet, my pop source doesn't let me chose the Cd attribute, or any attribute, for the emission. So I have a scatter points all over my object and I get the density that I want. Color it with Noise via PointVop. But I can't figure out how to make it only emit particles from the white points. I can get it to emit particles from all the points that match the color, but not controller which ones emit particles.

As far as I know it's not possible, however, you could scatter and have the particles inherit the emitter's uv's, then sample your image file and delete points from the resulting value.

Tanto
As far as I know it's not possible, however, you could scatter and have the particles inherit the emitter's uv's, then sample your image file and delete points from the resulting value.

I probably stated it incorrectly. Not really a texture map, I'm using a PointVop to apply a AA Noise Ramp as shown in the image just above.

This post talks about that:

https://www.sidefx.com/forum/topic/43467/ [www.sidefx.com]

But you could set your solver to points and cull in a wrangle with a cutoff before your target source.

BabaJ
This post talks about that:

https://www.sidefx.com/forum/topic/43467/ [www.sidefx.com]

But you could set your solver to points and cull in a wrangle with a cutoff before your target source.

Thank you. I thought there would be an easier, more direct way but I'll save this and refer back to it. I'm going to study it some more but I did learn enough to bind export and parameter out of the point VOP and put that in place of the luminance value you had so that I can use the color channel for it's intended purpose.

Thank you again for taking the time to look into this.