bool frustumCullingTest(mat4 mvp, vec3 bmin, vec3 bmax); struct Frustum { vec4 planes[6]; }; /** * Extract Frustum Planes from MVP Matrix * * Based on "Fast Extraction of Viewing Frustum Planes from the World- * View-Projection Matrix", by Gil Gribb and Klaus Hartmann. * This procedure computes the planes of the frustum and normalizes * them. */ void loadFrustum(out Frustum f, mat4 mvp) { for (int i = 0; i < 3; ++i) { for (int j = 0; j < 2; ++j) { f.planes[i*2+j].x = mtxGetElement(mvp, 0, 3) + (j == 0 ? mtxGetElement(mvp, 0, i) : -mtxGetElement(mvp, 0, i)); f.planes[i*2+j].y = mtxGetElement(mvp, 1, 3) + (j == 0 ? mtxGetElement(mvp, 1, i) : -mtxGetElement(mvp, 1, i)); f.planes[i*2+j].z = mtxGetElement(mvp, 2, 3) + (j == 0 ? mtxGetElement(mvp, 2, i) : -mtxGetElement(mvp, 2, i)); f.planes[i*2+j].w = mtxGetElement(mvp, 3, 3) + (j == 0 ? mtxGetElement(mvp, 3, i) : -mtxGetElement(mvp, 3, i)); f.planes[i*2+j]*= length(f.planes[i*2+j].xyz); } } } /** * Negative Vertex of an AABB * * This procedure computes the negative vertex of an AABB * given a normal. * See the View Frustum Culling tutorial @ LightHouse3D.com * http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-testing-boxes-ii/ */ vec3 negativeVertex(vec3 bmin, vec3 bmax, vec3 n) { bvec3 b = greaterThan(n, vec3(0.0, 0.0, 0.0)); return mix(bmin, bmax, b); } /** * Frustum-AABB Culling Test * * This procedure returns true if the AABB is either inside, or in * intersection with the frustum, and false otherwise. * The test is based on the View Frustum Culling tutorial @ LightHouse3D.com * http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-testing-boxes-ii/ */ bool frustumCullingTest(mat4 mvp, vec3 bmin, vec3 bmax) { float a = 1.0f; Frustum f; loadFrustum(f, mvp); for (int i = 0; i < 6 && a >= 0.0f; ++i) { vec3 n = negativeVertex(bmin, bmax, f.planes[i].xyz); a = dot(vec4(n, 1.0f), f.planes[i]); } return (a >= 0.0); }