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82 lines
2.1 KiB
C++
82 lines
2.1 KiB
C++
#include "math.h"
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namespace engine
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{
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bool engine::decomposeTransform(const math::mat4& transform, math::vec3& translation, math::vec3& rotation, math::vec3& scale)
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{
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using namespace math;
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using T = float;
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mat4 LocalMatrix(transform);
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// Normalize the matrix.
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if (epsilonEqual(LocalMatrix[3][3], static_cast<float>(0), epsilon<T>()))
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{
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return false;
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}
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// First, isolate perspective. This is the messiest.
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if (
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epsilonNotEqual(LocalMatrix[0][3], static_cast<T>(0), epsilon<T>()) ||
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epsilonNotEqual(LocalMatrix[1][3], static_cast<T>(0), epsilon<T>()) ||
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epsilonNotEqual(LocalMatrix[2][3], static_cast<T>(0), epsilon<T>()))
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{
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// Clear the perspective partition
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LocalMatrix[0][3] = LocalMatrix[1][3] = LocalMatrix[2][3] = static_cast<T>(0);
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LocalMatrix[3][3] = static_cast<T>(1);
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}
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// Next take care of translation (easy).
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translation = vec3(LocalMatrix[3]);
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LocalMatrix[3] = vec4(0, 0, 0, LocalMatrix[3].w);
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vec3 Row[3]{};//, Pdum3;
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// Now get scale and shear.
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for (length_t i = 0; i < 3; ++i)
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{
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for (length_t j = 0; j < 3; ++j)
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{
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Row[i][j] = LocalMatrix[i][j];
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}
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}
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// Compute X scale factor and normalize first row.
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scale.x = length(Row[0]);
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Row[0] = detail::scale(Row[0], static_cast<T>(1));
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scale.y = length(Row[1]);
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Row[1] = detail::scale(Row[1], static_cast<T>(1));
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scale.z = length(Row[2]);
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Row[2] = detail::scale(Row[2], static_cast<T>(1));
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// At this point, the matrix (in rows[]) is orthonormal.
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// Check for a coordinate system flip. If the determinant
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// is -1, then negate the matrix and the scaling factors.
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#if 0
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Pdum3 = cross(Row[1], Row[2]); // v3Cross(row[1], row[2], Pdum3);
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if (dot(Row[0], Pdum3) < 0)
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{
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for (length_t i = 0; i < 3; i++)
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{
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scale[i] *= static_cast<T>(-1);
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Row[i] *= static_cast<T>(-1);
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}
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}
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#endif
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rotation.y = asin(-Row[0][2]);
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if (cos(rotation.y) != 0.f)
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{
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rotation.x = atan2(Row[1][2], Row[2][2]);
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rotation.z = atan2(Row[0][1], Row[0][0]);
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}
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else
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{
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rotation.x = atan2(-Row[2][0], Row[1][1]);
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rotation.z = 0;
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}
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return true;
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}
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} |