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