77 lines
2.5 KiB
C
77 lines
2.5 KiB
C
/* SPDX-License-Identifier: Apache-2.0
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* Copyright 2011-2022 Blender Foundation */
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#pragma once
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CCL_NAMESPACE_BEGIN
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/* Custom cross and dot implementations that match Embree bit for bit.
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* Normally we don't use SSE41/AVX outside the kernel, but for this it's
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* important to match exactly for ray tracing precision. */
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ccl_device_forceinline float3 transform_inverse_cross(const float3 a, const float3 b)
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{
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#ifdef __AVX2__
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const ssef sse_a = (const __m128 &)a;
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const ssef sse_b = (const __m128 &)b;
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const ssef r = shuffle<1, 2, 0, 3>(
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ssef(_mm_fmsub_ps(sse_a, shuffle<1, 2, 0, 3>(sse_b), shuffle<1, 2, 0, 3>(sse_a) * sse_b)));
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return (const float3 &)r;
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#endif
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return cross(a, b);
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}
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ccl_device_forceinline float transform_inverse_dot(const float3 a, const float3 b)
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{
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#ifdef __SSE4_1__
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return _mm_cvtss_f32(_mm_dp_ps((const __m128 &)a, (const __m128 &)b, 0x7F));
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#endif
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return dot(a, b);
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}
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ccl_device_forceinline Transform transform_inverse_impl(const Transform tfm)
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{
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/* This implementation matches the one in Embree exactly, to ensure consistent
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* results with the ray intersection of instances. */
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float3 x = make_float3(tfm.x.x, tfm.y.x, tfm.z.x);
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float3 y = make_float3(tfm.x.y, tfm.y.y, tfm.z.y);
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float3 z = make_float3(tfm.x.z, tfm.y.z, tfm.z.z);
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float3 w = make_float3(tfm.x.w, tfm.y.w, tfm.z.w);
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/* Compute determinant. */
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float det = transform_inverse_dot(x, transform_inverse_cross(y, z));
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if (det == 0.0f) {
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/* Matrix is degenerate (e.g. 0 scale on some axis), ideally we should
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* never be in this situation, but try to invert it anyway with tweak.
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*
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* This logic does not match Embree which would just give an invalid
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* matrix. A better solution would be to remove this and ensure any object
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* matrix is valid. */
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x.x += 1e-8f;
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y.y += 1e-8f;
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z.z += 1e-8f;
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det = transform_inverse_dot(x, cross(y, z));
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if (det == 0.0f) {
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det = FLT_MAX;
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}
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}
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/* Divide adjoint matrix by the determinant to compute inverse of 3x3 matrix. */
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const float3 inverse_x = transform_inverse_cross(y, z) / det;
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const float3 inverse_y = transform_inverse_cross(z, x) / det;
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const float3 inverse_z = transform_inverse_cross(x, y) / det;
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/* Compute translation and fill transform. */
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Transform itfm;
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itfm.x = float3_to_float4(inverse_x, -transform_inverse_dot(inverse_x, w));
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itfm.y = float3_to_float4(inverse_y, -transform_inverse_dot(inverse_y, w));
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itfm.z = float3_to_float4(inverse_z, -transform_inverse_dot(inverse_z, w));
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return itfm;
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}
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CCL_NAMESPACE_END
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