Particle Question

I want to emit particles from the land masses on an earth model. Is there any way to select and delete vertices based on an image texture. I can do it on a plane using noise to push the proper vertices up, but I can’t figure out how to do it on a sphere. I tried the same method, but the vertices on the sphere only moved in the Z direction, not along vertex normals.

Damn, I have seen a tutorial that had exactly that topic, but I can’t remember where. I think it had to do with using the texture-related parameters of the particle system to keep certain particles at 0 speed, and giving the others movement depending on the intensity of the texture.

You could try using RVKs and flattening your sphere, then using the noise, then revert back to your base key. I have no idea if this will work.

The TrueDisplacement Python script could be used as a noise function along the normals.

I am very fuzzy on UV mapping, but the true displacement script seems to be a good solution. I did the tut on the site and got it to work, but I don’t know how to UV map onto a sphere. I get the entire texture on each face.

split the blender window in 2, make one side 3d view and other side uv mapping,
in the 3d view, go into uv face select mode and make sure the whole sphere is selected,
Press “u” in the 3d window, and select “from window to sphere”
in UV window load your image.

Way Cool!
I don’t even need the script to do that. I can just hand select the vertices and delete them right off the UV select screen.