/* * Copyright 2021 elven cache. All rights reserved. * License: https://github.com/bkaradzic/bgfx#license-bsd-2-clause */ #ifndef NORMAL_ENCODING_SH #define NORMAL_ENCODING_SH #define NE_USE_OCTAHEDRAL_REPRESENTATION 0 // From "A Survey of Efficient Representations for Independent Unit Vectors" // http://jcgt.org/published/0003/02/01/paper.pdf // Convert an oct24 (2x12bit normal) to an rgb8 value for storing in texture vec3 snorm12x2_to_unorm8x3 (vec2 f) { f = clamp(f, -1.0, 1.0);//min(max(f, vec2(-1.0)), vec2(1.0)); vec2 u = floor(f * 2047.0 + 2047.5); float t = floor(u.y / 256.0); // "This code assumes that rounding will occur during storage." // -- Not certain but this appears to mainly apply to the x channel. // From paper: x = u.x / 16.0 - 0.5 // Instead round by +0.5 and floor. return vec3(floor(u.x / 16.0), fract(u.x / 16.0) * 256.0 + t, u.y - t * 256.0) / 255.0; } // Unpack oct24 (2x12bit normal) from an rgb8 value stored in texture (normal spec) vec2 unorm8x3_to_snorm12x2 (vec3 u) { u *= 255.0; u.y *= (1.0 / 16.0); vec2 s = vec2(u.x * 16.0 + floor(u.y), fract(u.y) * (16.0 * 256.0) + u.z); s = s * (1.0 / 2047.0) - 1.0; return min(max(s, -1.0), 1.0); } // Built in sign test could return 0, don't want that vec2 signNotZero (vec2 v) { return vec2((v.x >= 0.0) ? 1.0 : -1.0, (v.y >= 0.0) ? 1.0 : -1.0); } // Assume normalized input. Output is (-1, 1) for each component vec2 float32x3_to_oct(vec3 v) { // Project the sphere onto the octahedron, and then onto the xy plane vec2 p = v.xy * (1.0 / (abs(v.x) + abs(v.y) + abs(v.z))); // Reflect the folds of the lower hemisphere over the diagonals return (v.z <= 0.0) ? ((1.0 - abs(p.yx)) * signNotZero(p)) : p; } // Get a float3 normal from an oct representation vec3 oct_to_float32x3 (vec2 e) { vec3 v = vec3(e.xy, 1.0 - abs(e.x) - abs(e.y)); if (v.z < 0.0) { v.xy = (1.0 - abs(v.yx)) * signNotZero(v.xy); } return normalize(v); } vec3 SignedNormalEncodeToOct (vec3 normal) { return snorm12x2_to_unorm8x3(float32x3_to_oct(normal)); } vec3 SignedNormalDecodeFromOct (vec3 normal) { return oct_to_float32x3(unorm8x3_to_snorm12x2(normal)); } vec3 NormalEncode (vec3 normal) { #if NE_USE_OCTAHEDRAL_REPRESENTATION return SignedNormalEncodeToOct(normal); #else return normal * 0.5 + 0.5; #endif } vec3 NormalDecode (vec3 normal) { #if NE_USE_OCTAHEDRAL_REPRESENTATION return SignedNormalDecodeFromOct(normal); #else return normal * 2.0 - 1.0; #endif } #endif // NORMAL_ENCODING_SH