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Merged
christophe-lunarg merged 3 commits into from
Dec 8, 2025
Merged

Implement #1370 (reflection matrix calculation) #1371

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8f504b7
Implement #1370 (reflection matrix calculation)
mariob92 May 21, 2025
0b600b2
Merge branch 'g-truc:master' into gtx_transform2/reflect
mariob92 Dec 7, 2025
b266749
Implement g-truc#1370 (reflection matrix calculation)
mariob92 Dec 7, 2025
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1 change: 1 addition & 0 deletions .gitignore
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,7 @@ test/gtc/*.dds
Makefile
*.cbp
*.user
.idea/

# Misc.
*.log
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12 changes: 9 additions & 3 deletions glm/gtx/transform2.hpp
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Expand Up @@ -57,9 +57,15 @@ namespace glm
// Identity + tan(angle) * cross(Normal, OnPlaneVector) 0
// - dot(PointOnPlane, normal) * OnPlaneVector 1

// Reflect functions seem to don't work
//template<typename T> mat<3, 3, T, Q> reflect2D(const mat<3, 3, T, Q> & m, const vec<3, T, Q>& normal){return reflect2DGTX(m, normal);} //!< \brief Build a reflection matrix (from GLM_GTX_transform2 extension)
//template<typename T> mat<4, 4, T, Q> reflect3D(const mat<4, 4, T, Q> & m, const vec<3, T, Q>& normal){return reflect3DGTX(m, normal);} //!< \brief Build a reflection matrix (from GLM_GTX_transform2 extension)
//! Reflects a matrix on an arbitrary plane.
//! From GLM_GTX_transform2 extension.
template<typename T, qualifier Q>
GLM_FUNC_DECL mat<3, 3, T, Q> reflect2D(mat<3, 3, T, Q> const& m, vec<2, T, Q> const& normal, T distance);

//! Reflects a matrix on an arbitrary plane.
//! From GLM_GTX_transform2 extension.
template<typename T, qualifier Q>
GLM_FUNC_DECL mat<4, 4, T, Q> reflect3D(mat<4, 4, T, Q> const& m, vec<3, T, Q> const& normal, T distance);

//! Build planar projection matrix along normal axis.
//! From GLM_GTX_transform2 extension.
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19 changes: 11 additions & 8 deletions glm/gtx/transform2.inl
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Expand Up @@ -46,31 +46,34 @@ namespace glm
}

template<typename T, qualifier Q>
GLM_FUNC_QUALIFIER mat<3, 3, T, Q> reflect2D(mat<3, 3, T, Q> const& m, vec<3, T, Q> const& normal)
GLM_FUNC_QUALIFIER mat<3, 3, T, Q> reflect2D(mat<3, 3, T, Q> const& m, vec<2, T, Q> const& normal, T distance)
{
mat<3, 3, T, Q> r(static_cast<T>(1));
r[0][0] = static_cast<T>(1) - static_cast<T>(2) * normal.x * normal.x;
r[0][1] = -static_cast<T>(2) * normal.x * normal.y;
r[0][1] = -static_cast<T>(2) * normal.y * normal.x;
r[1][0] = -static_cast<T>(2) * normal.x * normal.y;
r[1][1] = static_cast<T>(1) - static_cast<T>(2) * normal.y * normal.y;
r[2][0] = -static_cast<T>(2) * normal.x * distance;
r[2][1] = -static_cast<T>(2) * normal.y * distance;
return m * r;
}

template<typename T, qualifier Q>
GLM_FUNC_QUALIFIER mat<4, 4, T, Q> reflect3D(mat<4, 4, T, Q> const& m, vec<3, T, Q> const& normal)
GLM_FUNC_QUALIFIER mat<4, 4, T, Q> reflect3D(mat<4, 4, T, Q> const& m, vec<3, T, Q> const& normal, T distance)
{
mat<4, 4, T, Q> r(static_cast<T>(1));
r[0][0] = static_cast<T>(1) - static_cast<T>(2) * normal.x * normal.x;
r[0][1] = -static_cast<T>(2) * normal.x * normal.y;
r[0][2] = -static_cast<T>(2) * normal.x * normal.z;

r[0][1] = -static_cast<T>(2) * normal.y * normal.x;
r[0][2] = -static_cast<T>(2) * normal.z * normal.x;
r[1][0] = -static_cast<T>(2) * normal.x * normal.y;
r[1][1] = static_cast<T>(1) - static_cast<T>(2) * normal.y * normal.y;
r[1][2] = -static_cast<T>(2) * normal.y * normal.z;

r[1][2] = -static_cast<T>(2) * normal.z * normal.y;
r[2][0] = -static_cast<T>(2) * normal.x * normal.z;
r[2][1] = -static_cast<T>(2) * normal.y * normal.z;
r[2][2] = static_cast<T>(1) - static_cast<T>(2) * normal.z * normal.z;
r[3][0] = -static_cast<T>(2) * normal.x * distance;
r[3][1] = -static_cast<T>(2) * normal.y * distance;
r[3][2] = -static_cast<T>(2) * normal.z * distance;
return m * r;
}

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1 change: 1 addition & 0 deletions test/gtx/CMakeLists.txt
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Expand Up @@ -53,6 +53,7 @@ glmCreateTestGTC(gtx_spline)
glmCreateTestGTC(gtx_string_cast)
glmCreateTestGTC(gtx_structured_bindings)
glmCreateTestGTC(gtx_texture)
glmCreateTestGTC(gtx_transform2)
glmCreateTestGTC(gtx_type_aligned)
glmCreateTestGTC(gtx_type_trait)
glmCreateTestGTC(gtx_vec_swizzle)
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135 changes: 135 additions & 0 deletions test/gtx/gtx_transform2.cpp
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@@ -0,0 +1,135 @@
#include <glm/glm.hpp>
#include <glm/gtc/epsilon.hpp>

#define GLM_ENABLE_EXPERIMENTAL
#include <glm/gtx/transform2.hpp>

static int test_reflect2D()
{
int Error = 0;

{
const glm::mat3 m3(
1, 0, 0,
0, 1, 0,
1, 2, 1
);

const glm::mat3 eam3(
1, 0, 0,
0, -1, 0,
1, 2, 1
);

const glm::mat3 am3 = glm::reflect2D(
m3,
glm::vec2(0, 1),
static_cast<glm::mat3::row_type::value_type>(0)
);

Error += glm::all(glm::bvec3(
glm::all(glm::epsilonEqual(eam3[0], am3[0], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam3[1], am3[1], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam3[2], am3[2], glm::epsilon<float>())))) ? 0 : 1;
}

{
const glm::mat3 m3(
1, 0, 0,
0, 1, 0,
1, 2, 1
);

const glm::mat3 eam3(
0, 1, 0,
1, 0, 0,
1, 2, 1
);

const glm::mat3 am3 = glm::reflect2D(
m3,
glm::vec2(-0.70710678, 0.70710678),
static_cast<glm::mat3::row_type::value_type>(0)
);

Error += glm::all(glm::bvec3(
glm::all(glm::epsilonEqual(eam3[0], am3[0], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam3[1], am3[1], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam3[2], am3[2], glm::epsilon<float>())))) ? 0 : 1;
}

return Error;
}

static int test_reflect3D()
{
int Error = 0;

{
const glm::mat4 m4(
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
);

const glm::mat4 eam4(
1, 0, 0, 0,
0, -1, 0, 0,
0, 0, 1, 0,
0, -2, 0, 1
);

const glm::mat4 am4 = glm::reflect3D(
m4,
glm::vec3(0, 1, 0),
static_cast<glm::mat4::row_type::value_type>(1)
);

Error += glm::all(glm::bvec4(
glm::all(glm::epsilonEqual(eam4[0], am4[0], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam4[1], am4[1], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam4[2], am4[2], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam4[3], am4[3], glm::epsilon<float>())))) ? 0 : 1;
}

{
const glm::mat4 m4(
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
);

const glm::mat4 eam4(
0, 1, 0, 0,
1, 0, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
);

const glm::mat4 am4 = glm::reflect3D(
m4,
glm::vec3(-0.70710678, 0.70710678, 0.0),
static_cast<glm::mat4::row_type::value_type>(0)
);

Error += glm::all(glm::bvec4(
glm::all(glm::epsilonEqual(eam4[0], am4[0], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam4[1], am4[1], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam4[2], am4[2], glm::epsilon<float>())),
glm::all(glm::epsilonEqual(eam4[3], am4[3], glm::epsilon<float>())))) ? 0 : 1;
}

return Error;
}

int main()
{
int Error = 0;

Error += test_reflect2D();
Error += test_reflect3D();

return Error;
}