Function ray_mesh_intersection

src/core/math/intersection.cpp:153–213

}

f32 ray_mesh_intersection(const Vector3 &from, const Vector3 &dir, const Matrix4x4 &tm, const void *vertices, u32 stride, const u16 *indices, u32 num)
{
	bool hit = false;
	f32 tmin = FLT_MAX;

	for (u32 i = 0; i < num; i += 3) {
		const u32 i0 = indices[i + 0];
		const u32 i1 = indices[i + 1];
		const u32 i2 = indices[i + 2];

		const Vector3 &v0 = *(Vector3 *)((char *)vertices + i0*stride) * tm;
		const Vector3 &v1 = *(Vector3 *)((char *)vertices + i1*stride) * tm;
		const Vector3 &v2 = *(Vector3 *)((char *)vertices + i2*stride) * tm;

		// https://en.wikipedia.org/wiki/M%C3%B6ller%E2%80%93Trumbore_intersection_algorithm

		// Find vectors for two edges sharing v0
		const Vector3 e1 = v1 - v0;
		const Vector3 e2 = v2 - v0;

		// Begin calculating determinant - also used to calculate u parameter
		const Vector3 P = cross(dir, e2);

		// If determinant is near zero, ray lies in plane of triangle
		const f32 det = dot(e1, P);
		if (fequal(det, 0.0f))
			continue;

		const f32 inv_det = 1.0f / det;

		// Distance from v0 to ray origin
		const Vector3 T = from - v0;

		// u parameter and test bound
		const f32 u = dot(T, P) * inv_det;

		// The intersection lies outside of the triangle
		if (u < 0.0f || u > 1.0f)
			continue;

		// Prepare to test v parameter
		const Vector3 Q = cross(T, e1);

		// v parameter and test bound
		const f32 v = dot(dir, Q) * inv_det;

		// The intersection lies outside of the triangle
		if (v < 0.0f || u + v > 1.0f)
			continue;

		const f32 t = dot(e2, Q) * inv_det;

		// Ray intersection
		if (t > FLOAT_EPSILON) {
			hit = true;
			tmin = min(t, tmin);
		}
	}