Report Light frustums different in DR and TDM in DarkRadiant Feedback and Development Posted Thursday at 01:43 PM 2 hours ago, stgatilov said: No. We should differentiate between convention (is falloff in Z or W? should it be scaled by some number?) and behavior (shape of frustum, falloff value). Yes, the current code converts the matrix from BFG convention to D3 convention, but it does not & cannot convert behavior. And behaviors are different between D3 and BFG. If start/end vectors are not collinear with target vector, then you cannot convert D3 matrix in such a way that idRenderMatrix::ProjectedBounds/baseLightProject would work properly with the result. In BFG, light volume is always a frustum, but in D3 its near/far planes can be arbitrary. Maybe something can be hacked by making target vector non-orthogonal to R/U plane, but I'd better avoid that. Then what are we left with? It would be great to keep the render matrix stuff but you say it requires the BFG-constructed projection matrix? I suppose we should then change DR to use that method as well? Probably the only change should be the end pos being relative to origin rather than start to improve compatibility with the existing maps? Quote In BFG, light volume is always a frustum, but in D3 its near/far planes can be arbitrary. Sorry, what do you mean by that? Being a frustum means that near/far planes are parallel to XY or ???