How do you get a random point in a 3D plane
Given a quad like:
pD ---- pC
| |
| |
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pA ---- pB
You can get a random point by getting a random point within that normalized square and use the A-to-B and A-to-D vectors as a coordinate basis.
In practice:
// gets a value between 0.0 and 1.0
float randomVal();
vec3 point_in_quad(vec3 pA, vec3 pB, vec3 pC, vec3 pD) {
return pA + (pB - pA) * randomVal() + (pD - pA) * randomVal();
}