From a7cbe697124f12b24924b3d7f5e73a993e33509b Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Wed, 9 Jul 2025 21:02:22 +0300
Subject: [PATCH] Add math::trs class & use it in gltf animations

---
 .../gfx/include/psemek/gfx/gltf_animation.hpp |  6 +-
 libs/gfx/source/gltf_animation.cpp            |  6 +-
 libs/math/include/psemek/math/trs.hpp         | 88 +++++++++++++++++++
 3 files changed, 92 insertions(+), 8 deletions(-)
 create mode 100644 libs/math/include/psemek/math/trs.hpp

diff --git a/libs/gfx/include/psemek/gfx/gltf_animation.hpp b/libs/gfx/include/psemek/gfx/gltf_animation.hpp
index ac5f95b7..df3e8491 100644
--- a/libs/gfx/include/psemek/gfx/gltf_animation.hpp
+++ b/libs/gfx/include/psemek/gfx/gltf_animation.hpp
@@ -1,9 +1,7 @@
 #pragma once
 
 #include <psemek/gfx/gltf_parser.hpp>
-#include <psemek/math/scale.hpp>
-#include <psemek/math/rotation.hpp>
-#include <psemek/math/translation.hpp>
+#include <psemek/math/trs.hpp>
 #include <psemek/util/exception.hpp>
 
 #include <algorithm>
@@ -147,7 +145,7 @@ namespace psemek::gfx
 
 		math::interval<float> range() const;
 
-		math::affine_transform<float, 3, 3> operator()(float time) const;
+		math::trs<float, 3> operator()(float time) const;
 
 		gltf_scale_animation const & scale() const { return scale_; }
 		gltf_rotation_animation const & rotation() const { return rotation_; }
diff --git a/libs/gfx/source/gltf_animation.cpp b/libs/gfx/source/gltf_animation.cpp
index bfd28800..efb2f351 100644
--- a/libs/gfx/source/gltf_animation.cpp
+++ b/libs/gfx/source/gltf_animation.cpp
@@ -90,11 +90,9 @@ namespace psemek::gfx
 		return scale_.range() | rotation_.range() | translation_.range();
 	}
 
-	math::affine_transform<float, 3, 3> gltf_animation::operator()(float time) const
+	math::trs<float, 3> gltf_animation::operator()(float time) const
 	{
-		return math::translation(translation_(time)).transform()
-			* math::quaternion_rotation(rotation_(time)).transform()
-			* math::scale(scale_(time)).transform();
+		return {translation_(time), rotation_(time), scale_(time)};
 	}
 
 }
diff --git a/libs/math/include/psemek/math/trs.hpp b/libs/math/include/psemek/math/trs.hpp
new file mode 100644
index 00000000..20593728
--- /dev/null
+++ b/libs/math/include/psemek/math/trs.hpp
@@ -0,0 +1,88 @@
+#pragma once
+
+#include <psemek/math/scale.hpp>
+#include <psemek/math/rotation.hpp>
+#include <psemek/math/translation.hpp>
+
+namespace psemek::math
+{
+
+	// NB: composition of TRS triplets is not defined as the result
+	//     might not be expressible in TRS form
+
+	template <typename T, std::size_t N>
+	struct trs;
+
+	template <typename T>
+	struct trs<T, 3>
+	{
+		vector<T, 3> translation;
+		quaternion<T> rotation;
+		vector<T, 3> scale;
+
+		static trs<T, 3> identity()
+		{
+			return {vector<T, 3>::zero(), quaternion<T>::identity(), vector{T{1}, T{1}, T{1}}};
+		}
+
+		static trs<T, 3> from(matrix<T, 3, 4> const & m)
+		{
+			trs<T, 3> result;
+
+			result.translation[0] = m[0][3];
+			result.translation[1] = m[1][3];
+			result.translation[2] = m[2][3];
+
+			result.scale[0] = length(vector{m[0][0], m[1][0], m[2][0]});
+			result.scale[1] = length(vector{m[0][1], m[1][1], m[2][1]});
+			result.scale[2] = length(vector{m[0][2], m[1][2], m[2][2]});
+
+			matrix<T, 3, 3> r;
+			for (int i = 0; i < 3; ++i)
+				for (int j = 0; j < 3; ++j)
+					r[i][j] = m[i][j] / result.scale[j];
+
+			result.rotation = quaternion<T>::rotation(r);
+
+			return result;
+		}
+
+		matrix<T, 3, 4> affine_matrix() const
+		{
+			return transform().affine_matrix();
+		}
+
+		matrix<T, 3, 3> linear_matrix() const
+		{
+			return transform().linear_matrix();
+		}
+
+		vector<T, 3> translation_vector() const
+		{
+			return translation;
+		}
+
+		matrix<T, 4, 4> homogeneous_matrix() const
+		{
+			return transform().homogeneous_matrix();
+		}
+
+		vector<T, 3> operator()(vector<T, 3> const & v) const
+		{
+			return rotate(rotation, pointwise_mult(v, scale));
+		}
+
+		point<T, 3> operator()(point<T, 3> const & p) const
+		{
+			return p.zero() + rotate(rotation, pointwise_mult(p - p.zero(), scale)) + translation;
+		}
+
+		affine_transform<T, 3, 3> transform() const
+		{
+			return math::translation(translation).transform()
+				* quaternion_rotation(rotation).transform()
+				* math::scale(scale).transform();
+		}
+	};
+
+}