07-14-2020, 08:20 AM
I think this would be better suited for a Script operator, where you can use the built-in raycasting functions and texture sampling functions exposed in the API to have exact control over particle positions on surfaces. If you wanted to limit how far away a particle can move, you'd first cast your ray against the object, check the length of the vector between the rayhit point and the particle position, and if the ray length is beyond a certain length, you'd normalize the vector and then multiply it by the max length. Then you'd assign the new position to the particle by adding the vector to its currently position.