From 063e8e43ba8253fede32b8745d1406957b3eb501 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Sun, 26 Mar 2023 23:51:51 +0300
Subject: [PATCH] glTF animations

---
 .../gfx/include/psemek/gfx/gltf_animation.hpp | 169 ++++++++++++++++++
 libs/gfx/include/psemek/gfx/gltf_parser.hpp   |  14 +-
 libs/gfx/source/gltf_parser.cpp               |  12 ++
 3 files changed, 193 insertions(+), 2 deletions(-)
 create mode 100644 libs/gfx/include/psemek/gfx/gltf_animation.hpp

diff --git a/libs/gfx/include/psemek/gfx/gltf_animation.hpp b/libs/gfx/include/psemek/gfx/gltf_animation.hpp
new file mode 100644
index 00000000..22514385
--- /dev/null
+++ b/libs/gfx/include/psemek/gfx/gltf_animation.hpp
@@ -0,0 +1,169 @@
+#pragma once
+
+#include <psemek/gfx/gltf_parser.hpp>
+#include <psemek/geom/scale.hpp>
+#include <psemek/geom/rotation.hpp>
+#include <psemek/geom/translation.hpp>
+
+#include <algorithm>
+
+namespace psemek::gfx
+{
+
+	namespace detail
+	{
+
+		template <gltf_asset::animation::channel::path_t path>
+		struct gltf_animation_traits;
+
+		template <>
+		struct gltf_animation_traits<gltf_asset::animation::channel::scale>
+		{
+			using output_type = geom::vector<float, 3>;
+
+			static output_type default_value()
+			{
+				return {1.f, 1.f, 1.f};
+			}
+
+			static output_type lerp(output_type const & v1, output_type const & v2, float t)
+			{
+				return geom::lerp(v1, v2, t);
+			}
+		};
+
+		template <>
+		struct gltf_animation_traits<gltf_asset::animation::channel::rotation>
+		{
+			using output_type = geom::quaternion<float>;
+
+			static output_type default_value()
+			{
+				return output_type::identity();
+			}
+
+			static output_type lerp(output_type const & v1, output_type const & v2, float t)
+			{
+				return geom::slerp(v1, v2, t);
+			}
+		};
+
+		template <>
+		struct gltf_animation_traits<gltf_asset::animation::channel::translation>
+		{
+			using output_type = geom::vector<float, 3>;
+
+			static output_type default_value()
+			{
+				return {0.f, 0.f, 0.f};
+			}
+
+			static output_type lerp(output_type const & v1, output_type const & v2, float t)
+			{
+				return geom::lerp(v1, v2, t);
+			}
+		};
+
+	}
+
+	template <gltf_asset::animation::channel::path_t path>
+	struct gltf_animation_channel
+	{
+		using traits = detail::gltf_animation_traits<path>;
+		using output_type = typename traits::output_type;
+
+		gltf_animation_channel()
+			: input_{0.f}
+			, output_{traits::default_value()}
+			, interpolation_{geom::easing_type::constant_left}
+		{}
+
+		gltf_animation_channel(std::vector<float> input, std::vector<output_type> output, geom::easing_type interpolation)
+			: input_(std::move(input))
+			, output_(std::move(output))
+			, interpolation_(interpolation)
+		{}
+
+		gltf_animation_channel(gltf_animation_channel &&) = default;
+
+		gltf_animation_channel & operator = (gltf_animation_channel &&) = default;
+
+		geom::interval<float> range() const
+		{
+			return {input_.front(), input_.back()};
+		}
+
+		output_type operator()(float time) const
+		{
+			auto it = std::lower_bound(input_.begin(), input_.end(), time);
+			if (it == input_.begin())
+				return output_.back();
+			if (it == input_.end())
+				return output_.back();
+
+			auto i = it - input_.begin();
+
+			float t = (time - input_[i - 1]) / (input_[i] - input_[i - 1]);
+
+			switch (interpolation_)
+			{
+			case geom::easing_type::constant_left:
+				return output_[i - 1];
+			case geom::easing_type::linear:
+				return traits::lerp(output_[i - 1], output_[i], t);
+			case geom::easing_type::cubic:
+				{
+					// see https://github.khronos.org/glTF-Tutorials/gltfTutorial/gltfTutorial_007_Animations.html#cubic-spline-interpolation
+					float t2 = t * t;
+					float t3 = t * t2;
+					return traits::default_value()
+						+ output_[3 * (i - 1) + 1] * (  2.f * t3 - 3.f * t2 + 1.f)
+						+ output_[3 * (i - 1) + 2] * (        t3 - 2.f * t2 + t  )
+						+ output_[3 * (i + 0) + 1] * (- 2.f * t3 + 3.f * t2      )
+						+ output_[3 * (i + 0) + 0] * (        t3 -       t2      )
+						;
+				}
+			default:
+				throw std::runtime_error("unsupported glTF animation interpolation type");
+			}
+		}
+
+	private:
+		std::vector<float> input_;
+		std::vector<output_type> output_;
+		geom::easing_type interpolation_;
+	};
+
+	using gltf_scale_animation = gltf_animation_channel<gltf_asset::animation::channel::scale>;
+	using gltf_rotation_animation = gltf_animation_channel<gltf_asset::animation::channel::rotation>;
+	using gltf_translation_animation = gltf_animation_channel<gltf_asset::animation::channel::translation>;
+
+	struct gltf_animation
+	{
+		gltf_animation() = default;
+
+		gltf_animation(gltf_scale_animation scale, gltf_rotation_animation rotation, gltf_translation_animation translation)
+			: scale_(std::move(scale))
+			, rotation_(std::move(rotation))
+			, translation_(std::move(translation))
+		{}
+
+		geom::interval<float> range() const
+		{
+			return scale_.range() | rotation_.range() | translation_.range();
+		}
+
+		geom::affine_transform<float, 3, 3> operator()(float time) const
+		{
+			return geom::translation(translation_(time)).transform()
+				* geom::quaternion_rotation(rotation_(time)).transform()
+				* geom::scale(scale_(time)).transform();
+		}
+
+	private:
+		gltf_scale_animation scale_;
+		gltf_rotation_animation rotation_;
+		gltf_translation_animation translation_;
+	};
+
+}
diff --git a/libs/gfx/include/psemek/gfx/gltf_parser.hpp b/libs/gfx/include/psemek/gfx/gltf_parser.hpp
index 216a42fd..64d13c22 100644
--- a/libs/gfx/include/psemek/gfx/gltf_parser.hpp
+++ b/libs/gfx/include/psemek/gfx/gltf_parser.hpp
@@ -4,6 +4,7 @@
 #include <psemek/gfx/color.hpp>
 #include <psemek/geom/vector.hpp>
 #include <psemek/geom/quaternion.hpp>
+#include <psemek/geom/affine_transform.hpp>
 #include <psemek/geom/easing.hpp>
 
 #include <vector>
@@ -29,6 +30,7 @@ namespace psemek::gfx
 			geom::vector<float, 3> translation;
 			geom::quaternion<float> rotation;
 			geom::vector<float, 3> scale;
+			geom::affine_transform<float, 3, 3> transform;
 		};
 
 		struct mesh
@@ -156,8 +158,16 @@ namespace psemek::gfx
 		std::vector<buffer> buffers;
 		std::vector<light> lights; // KHR_lights_punctual
 
-		std::unordered_map<std::string, std::size_t> node_index;
-		std::unordered_map<std::string, std::size_t> material_index;
+		std::unordered_map<std::string, std::size_t> node_index; // node by name
+		std::unordered_map<std::string, std::size_t> material_index; // material by name
+
+		struct animation_and_channel
+		{
+			std::size_t animation;
+			std::size_t channel;
+		};
+
+		std::vector<std::vector<animation_and_channel>> node_animations; // node to list of animation channels that affect it
 	};
 
 	gltf_asset parse_gltf(io::istream && stream);
diff --git a/libs/gfx/source/gltf_parser.cpp b/libs/gfx/source/gltf_parser.cpp
index 09c845a3..553155d1 100644
--- a/libs/gfx/source/gltf_parser.cpp
+++ b/libs/gfx/source/gltf_parser.cpp
@@ -1,4 +1,7 @@
 #include <psemek/gfx/gltf_parser.hpp>
+#include <psemek/geom/scale.hpp>
+#include <psemek/geom/rotation.hpp>
+#include <psemek/geom/translation.hpp>
 #include <psemek/util/to_string.hpp>
 
 #include <boost/preprocessor/stringize.hpp>
@@ -122,6 +125,10 @@ namespace psemek::gfx
 					target.scale[i] = scale[i].GetFloat();
 			}
 
+			target.transform = geom::translation(target.translation).transform()
+				* geom::quaternion_rotation(target.rotation).transform()
+				* geom::scale(target.scale).transform();
+
 			if (node.HasMember("children"))
 			{
 				for (auto const & child : node["children"].GetArray())
@@ -357,6 +364,11 @@ namespace psemek::gfx
 		for (std::size_t i = 0; i < result.materials.size(); ++i)
 			result.material_index[result.materials[i].name] = i;
 
+		result.node_animations.resize(result.nodes.size());
+		for (std::size_t i = 0; i < result.animations.size(); ++i)
+			for (std::size_t j = 0; j < result.animations[i].channels.size(); ++j)
+				result.node_animations[result.animations[i].channels[j].target].push_back({i, j});
+
 		return result;
 	}