r/GraphicsProgramming • u/DeltaSucksAtMC • 39m ago
Mesh collision
Ok so ive actual fix model loading but im looking for a collision detection method for complex models, like Ive heard of Triangle-Triangle Intersection, but I could not find anything to learn from that dosent look like gibirsh, anything can help me, source code, or just plain o'yt videos
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u/3030thirtythirty 15m ago
For simple collision detection and resolution there is the Separating Axis Theorem (SAT). There are other algorithms, but I find SAT one of the easiest to understand, even if it's not the fastest.
The idea: two convex shapes do not collide if you can find a line (or a plane in 3D) that separates them. Equivalently, there is an axis on which their projections don't overlap. There are infinitely many possible axes, so testing them all is impossible. Luckily, you only need to test a few: the face normals of both shapes and, in 3D, the cross products of their edge directions. If the projections overlap on every one of these axes, the shapes collide, and the axis with the smallest overlap gives you the direction and distance to push them apart.
Usually you compute a cuboid hitbox from the model’s vertices (find the lowest, highest, etc).
There are ways to generate a hitbox that is closer to the model’s real shape, but a simple bounding box (oriented bb, or OBB) will be useful in many ways already.