- var intersect = "\n\nuniform sampler2D positions;\nuniform sampler2D normals;\nuniform sampler2D uvs;\nuniform sampler2D bvh;\n\nstruct Triangle {\n vec3 p0;\n vec3 p1;\n vec3 p2;\n};\n\nvoid surfaceInteractionFromBVH(inout SurfaceInteraction si, Triangle tri, vec3 barycentric, ivec3 index, vec3 faceNormal, int materialIndex) {\n si.hit = true;\n si.faceNormal = faceNormal;\n si.position = barycentric.x * tri.p0 + barycentric.y * tri.p1 + barycentric.z * tri.p2;\n ivec2 i0 = unpackTexel(index.x, VERTEX_COLUMNS);\n ivec2 i1 = unpackTexel(index.y, VERTEX_COLUMNS);\n ivec2 i2 = unpackTexel(index.z, VERTEX_COLUMNS);\n\n vec3 n0 = texelFetch(normals, i0, 0).xyz;\n vec3 n1 = texelFetch(normals, i1, 0).xyz;\n vec3 n2 = texelFetch(normals, i2, 0).xyz;\n vec3 normal = normalize(barycentric.x * n0 + barycentric.y * n1 + barycentric.z * n2);\n\n #if defined(NUM_DIFFUSE_MAPS) || defined(NUM_NORMAL_MAPS) || defined(NUM_PBR_MAPS)\n vec2 uv0 = texelFetch(uvs, i0, 0).xy;\n vec2 uv1 = texelFetch(uvs, i1, 0).xy;\n vec2 uv2 = texelFetch(uvs, i2, 0).xy;\n vec2 uv = fract(barycentric.x * uv0 + barycentric.y * uv1 + barycentric.z * uv2);\n #else\n vec2 uv = vec2();\n #endif\n\n si.materialType = int(getMatType(materialIndex));\n si.color = getMatColor(materialIndex, uv);\n si.roughness = getMatRoughness(materialIndex, uv);\n si.metalness = getMatMetalness(materialIndex, uv);\n\n #ifdef NUM_NORMAL_MAPS\n vec3 dp1 = tri.p0 - tri.p2;\n vec3 dp2 = tri.p1 - tri.p2;\n vec2 duv1 = uv0 - uv2;\n vec2 duv2 = uv1 - uv2;\n si.normal = getMatNormal(materialIndex, uv, normal, dp1, dp2, duv1, duv2);\n #else\n si.normal = normal;\n #endif\n}\n\nstruct TriangleIntersect {\n float t;\n vec3 barycentric;\n};\n\n// Triangle-ray intersection\n// Faster than the classic M\xF6ller\u2013Trumbore intersection algorithm\n// http://www.pbr-book.org/3ed-2018/Shapes/Triangle_Meshes.html#TriangleIntersection\nTriangleIntersect intersectTriangle(Ray r, Triangle tri, int maxDim, vec3 shear) {\n TriangleIntersect ti;\n vec3 d = r.d;\n\n // translate vertices based on ray origin\n vec3 p0t = tri.p0 - r.o;\n vec3 p1t = tri.p1 - r.o;\n vec3 p2t = tri.p2 - r.o;\n\n // permute components of triangle vertices\n if (maxDim == 0) {\n p0t = p0t.yzx;\n p1t = p1t.yzx;\n p2t = p2t.yzx;\n } else if (maxDim == 1) {\n p0t = p0t.zxy;\n p1t = p1t.zxy;\n p2t = p2t.zxy;\n }\n\n // apply shear transformation to translated vertex positions\n p0t.xy += shear.xy * p0t.z;\n p1t.xy += shear.xy * p1t.z;\n p2t.xy += shear.xy * p2t.z;\n\n // compute edge function coefficients\n vec3 e = vec3(\n p1t.x * p2t.y - p1t.y * p2t.x,\n p2t.x * p0t.y - p2t.y * p0t.x,\n p0t.x * p1t.y - p0t.y * p1t.x\n );\n\n // check if intersection is inside triangle\n if (any(lessThan(e, vec3(0))) && any(greaterThan(e, vec3(0)))) {\n return ti;\n }\n\n float det = e.x + e.y + e.z;\n\n // not needed?\n // if (det == 0.) {\n // return ti;\n // }\n\n p0t.z *= shear.z;\n p1t.z *= shear.z;\n p2t.z *= shear.z;\n float tScaled = (e.x * p0t.z + e.y * p1t.z + e.z * p2t.z);\n\n // not needed?\n // if (sign(det) != sign(tScaled)) {\n // return ti;\n // }\n\n // check if closer intersection already exists\n if (abs(tScaled) > abs(r.tMax * det)) {\n return ti;\n }\n\n float invDet = 1. / det;\n ti.t = tScaled * invDet;\n ti.barycentric = e * invDet;\n\n return ti;\n}\n\nstruct Box {\n vec3 min;\n vec3 max;\n};\n\n// Branchless ray/box intersection\n// https://tavianator.com/fast-branchless-raybounding-box-intersections/\nfloat intersectBox(Ray r, Box b) {\n vec3 tBot = (b.min - r.o) * r.invD;\n vec3 tTop = (b.max - r.o) * r.invD;\n vec3 tNear = min(tBot, tTop);\n vec3 tFar = max(tBot, tTop);\n float t0 = max(tNear.x, max(tNear.y, tNear.z));\n float t1 = min(tFar.x, min(tFar.y, tFar.z));\n\n return (t0 > t1 || t0 > r.tMax) ? -1.0 : (t0 > 0.0 ? t0 : t1);\n}\n\nint maxDimension(vec3 v) {\n return v.x > v.y ? (v.x > v.z ? 0 : 2) : (v.y > v.z ? 1 : 2);\n}\n\n// Traverse BVH, find closest triangle intersection, and return surface information\nvoid intersectScene(inout Ray ray, inout SurfaceInteraction si) {\n si.hit = false;\n\n int maxDim = maxDimension(abs(ray.d));\n\n // Permute space so that the z dimension is the one where the absolute value of the ray's direction is largest.\n // Then create a shear transformation that aligns ray direction with the +z axis\n vec3 shear;\n if (maxDim == 0) {\n shear = vec3(-ray.d.y, -ray.d.z, 1.0) * ray.invD.x;\n } else if (maxDim == 1) {\n shear = vec3(-ray.d.z, -ray.d.x, 1.0) * ray.invD.y;\n } else {\n shear = vec3(-ray.d.x, -ray.d.y, 1.0) * ray.invD.z;\n }\n\n int nodesToVisit[STACK_SIZE];\n int stack = 0;\n\n nodesToVisit[0] = 0;\n\n while(stack >= 0) {\n int i = nodesToVisit[stack--];\n\n vec4 r1 = fetchData(bvh, i, BVH_COLUMNS);\n vec4 r2 = fetchData(bvh, i + 1, BVH_COLUMNS);\n\n int splitAxisOrNumPrimitives = floatBitsToInt(r1.w);\n\n if (splitAxisOrNumPrimitives >= 0) {\n // Intersection is a bounding box. Test for box intersection and keep traversing BVH\n int splitAxis = splitAxisOrNumPrimitives;\n\n Box bbox = Box(r1.xyz, r2.xyz);\n\n if (intersectBox(ray, bbox) > 0.0) {\n // traverse near node to ray first, and far node to ray last\n if (ray.d[splitAxis] > 0.0) {\n nodesToVisit[++stack] = floatBitsToInt(r2.w);\n nodesToVisit[++stack] = i + 2;\n } else {\n nodesToVisit[++stack] = i + 2;\n nodesToVisit[++stack] = floatBitsToInt(r2.w);\n }\n }\n } else {\n ivec3 index = floatBitsToInt(r1.xyz);\n Triangle tri = Triangle(\n fetchData(positions, index.x, VERTEX_COLUMNS).xyz,\n fetchData(positions, index.y, VERTEX_COLUMNS).xyz,\n fetchData(positions, index.z, VERTEX_COLUMNS).xyz\n );\n TriangleIntersect hit = intersectTriangle(ray, tri, maxDim, shear);\n\n if (hit.t > 0.0) {\n ray.tMax = hit.t;\n int materialIndex = floatBitsToInt(r2.w);\n vec3 faceNormal = r2.xyz;\n surfaceInteractionFromBVH(si, tri, hit.barycentric, index, faceNormal, materialIndex);\n }\n }\n }\n\n // Values must be clamped outside of intersection loop. Clamping inside the loop produces incorrect numbers on some devices.\n si.roughness = clamp(si.roughness, ROUGHNESS_MIN, 1.0);\n si.metalness = clamp(si.metalness, 0.0, 1.0);\n}\n\nbool intersectSceneShadow(inout Ray ray) {\n int maxDim = maxDimension(abs(ray.d));\n\n // Permute space so that the z dimension is the one where the absolute value of the ray's direction is largest.\n // Then create a shear transformation that aligns ray direction with the +z axis\n vec3 shear;\n if (maxDim == 0) {\n shear = vec3(-ray.d.y, -ray.d.z, 1.0) * ray.invD.x;\n } else if (maxDim == 1) {\n shear = vec3(-ray.d.z, -ray.d.x, 1.0) * ray.invD.y;\n } else {\n shear = vec3(-ray.d.x, -ray.d.y, 1.0) * ray.invD.z;\n }\n\n int nodesToVisit[STACK_SIZE];\n int stack = 0;\n\n nodesToVisit[0] = 0;\n\n while(stack >= 0) {\n int i = nodesToVisit[stack--];\n\n vec4 r1 = fetchData(bvh, i, BVH_COLUMNS);\n vec4 r2 = fetchData(bvh, i + 1, BVH_COLUMNS);\n\n int splitAxisOrNumPrimitives = floatBitsToInt(r1.w);\n\n if (splitAxisOrNumPrimitives >= 0) {\n int splitAxis = splitAxisOrNumPrimitives;\n\n Box bbox = Box(r1.xyz, r2.xyz);\n\n if (intersectBox(ray, bbox) > 0.0) {\n if (ray.d[splitAxis] > 0.0) {\n nodesToVisit[++stack] = floatBitsToInt(r2.w);\n nodesToVisit[++stack] = i + 2;\n } else {\n nodesToVisit[++stack] = i + 2;\n nodesToVisit[++stack] = floatBitsToInt(r2.w);\n }\n }\n } else {\n ivec3 index = floatBitsToInt(r1.xyz);\n Triangle tri = Triangle(\n fetchData(positions, index.x, VERTEX_COLUMNS).xyz,\n fetchData(positions, index.y, VERTEX_COLUMNS).xyz,\n fetchData(positions, index.z, VERTEX_COLUMNS).xyz\n );\n\n if (intersectTriangle(ray, tri, maxDim, shear).t > 0.0) {\n return true;\n }\n }\n }\n\n return false;\n}\n\n";
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