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/* SPDX-License-Identifier: Apache-2.0
* Copyright 2011-2022 Blender Foundation */
#pragma once
CCL_NAMESPACE_BEGIN
/* Custom cross and dot implementations that match Embree bit for bit.
* Normally we don't use SSE41/AVX outside the kernel, but for this it's
* important to match exactly for ray tracing precision. */
ccl_device_forceinline float3 transform_inverse_cross(const float3 a_, const float3 b_)
{
#if defined(__AVX2__) && defined(__KERNEL_SSE2__)
const __m128 a = (const __m128 &)a_;
const __m128 b = (const __m128 &)b_;
const __m128 a_shuffle = _mm_castsi128_ps(
_mm_shuffle_epi32(_mm_castps_si128(a), _MM_SHUFFLE(3, 0, 2, 1)));
const __m128 b_shuffle = _mm_castsi128_ps(
_mm_shuffle_epi32(_mm_castps_si128(b), _MM_SHUFFLE(3, 0, 2, 1)));
const __m128 r = _mm_castsi128_ps(
_mm_shuffle_epi32(_mm_castps_si128(_mm_fmsub_ps(a, b_shuffle, _mm_mul_ps(a_shuffle, b))),
_MM_SHUFFLE(3, 0, 2, 1)));
return (const float3 &)r;
#endif
return cross(a_, b_);
}
ccl_device_forceinline float transform_inverse_dot(const float3 a_, const float3 b_)
{
#if defined(__KERNEL_SSE__) && defined(__KERNEL_SSE41__)
const __m128 a = (const __m128 &)a_;
const __m128 b = (const __m128 &)b_;
return _mm_cvtss_f32(_mm_dp_ps(a, b, 0x7F));
#endif
return dot(a_, b_);
}
ccl_device_forceinline Transform transform_inverse_impl(const Transform tfm)
{
/* This implementation matches the one in Embree exactly, to ensure consistent
* results with the ray intersection of instances. */
float3 x = make_float3(tfm.x.x, tfm.y.x, tfm.z.x);
float3 y = make_float3(tfm.x.y, tfm.y.y, tfm.z.y);
float3 z = make_float3(tfm.x.z, tfm.y.z, tfm.z.z);
float3 w = make_float3(tfm.x.w, tfm.y.w, tfm.z.w);
/* Compute determinant. */
float det = transform_inverse_dot(x, transform_inverse_cross(y, z));
if (det == 0.0f) {
/* Matrix is degenerate (e.g. 0 scale on some axis), ideally we should
* never be in this situation, but try to invert it anyway with tweak.
*
* This logic does not match Embree which would just give an invalid
* matrix. A better solution would be to remove this and ensure any object
* matrix is valid. */
x.x += 1e-8f;
y.y += 1e-8f;
z.z += 1e-8f;
det = transform_inverse_dot(x, cross(y, z));
if (det == 0.0f) {
det = FLT_MAX;
}
}
/* Divide adjoint matrix by the determinant to compute inverse of 3x3 matrix. */
const float3 inverse_x = transform_inverse_cross(y, z) / det;
const float3 inverse_y = transform_inverse_cross(z, x) / det;
const float3 inverse_z = transform_inverse_cross(x, y) / det;
/* Compute translation and fill transform. */
Transform itfm;
itfm.x = float3_to_float4(inverse_x, -transform_inverse_dot(inverse_x, w));
itfm.y = float3_to_float4(inverse_y, -transform_inverse_dot(inverse_y, w));
itfm.z = float3_to_float4(inverse_z, -transform_inverse_dot(inverse_z, w));
return itfm;
}
CCL_NAMESPACE_END
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