From b25bc3cc32c5a9057c66ad282fa1cdfe0ed6094a Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Mon, 10 Apr 2023 18:45:13 +0100
Subject: First cut loading assets using assimp

This is far from perfect, specifically the created texture atlas is not compatibile with wrapping texture UVs
---
 assetFactory/assimp.cpp | 119 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 assetFactory/assimp.cpp

(limited to 'assetFactory/assimp.cpp')

diff --git a/assetFactory/assimp.cpp b/assetFactory/assimp.cpp
new file mode 100644
index 0000000..55090f4
--- /dev/null
+++ b/assetFactory/assimp.cpp
@@ -0,0 +1,119 @@
+#include "assimp.h"
+#include "assetFactory.h"
+#include "collections.hpp"
+#include "ptr.hpp"
+#include "resource.h"
+#include <assimp/cimport.h>
+#include <assimp/postprocess.h>
+#include <assimp/scene.h>
+#include <stb/stb_image.h>
+
+template<typename T>
+glm::vec<3, T>
+operator*(const aiVector3t<T> & v)
+{
+	return {v.x, v.y, v.z};
+}
+
+template<typename T>
+glm::vec<2, T>
+operator!(const aiVector3t<T> & v)
+{
+	return {v.x, v.y};
+}
+
+#define AIRANGE(parent, member) \
+	std::span \
+	{ \
+		(parent)->m##member, (parent)->mNum##member \
+	}
+
+using ScemeCPtr = std::shared_ptr<const aiScene>;
+class AssImpNode : public Shape {
+public:
+	AssImpNode(ScemeCPtr scene, const aiNode * node) : scene(std::move(scene)), node(node) { }
+
+	ScemeCPtr scene;
+	const aiNode * node;
+
+	CreatedFaces
+	createMesh(ModelFactoryMesh & mesh, float) const
+	{
+		CreatedFaces faces;
+		addMesh(faces, mesh, node);
+		return faces;
+	}
+
+	void
+	addMesh(CreatedFaces & faces, ModelFactoryMesh & mesh, const aiNode * node) const
+	{
+		for (const auto & m : AIRANGE(node, Meshes)) {
+			addMesh(faces, mesh, scene->mMeshes[m]);
+		}
+		for (const auto & n : AIRANGE(node, Children)) {
+			addMesh(faces, mesh, n);
+		}
+	}
+
+	void
+	addMesh(CreatedFaces & faces, ModelFactoryMesh & mesh, const aiMesh * amesh) const
+	{
+		const auto vhs = AIRANGE(amesh, Vertices) * [&mesh](auto && v) {
+			return mesh.add_vertex(*v);
+		};
+		const auto & m = *scene->mMaterials[amesh->mMaterialIndex];
+
+		AssetFactory::TextureFragmentCoords tfc;
+		if (auto mf = Persistence::ParseBase::getShared<AssetFactory>("assetFactory")) {
+			aiString path;
+			m.Get(AI_MATKEY_TEXTURE_DIFFUSE(0), path);
+			tfc = mf->getTextureCoords(path.C_Str());
+		}
+
+		for (const auto & f : AIRANGE(amesh, Faces)) {
+			const auto fvhs = AIRANGE(&f, Indices) * [&vhs](auto && i) {
+				return vhs[i];
+			};
+			const auto fh = faces.emplace(mesh.add_namedFace(amesh->mName.C_Str(), fvhs))->second;
+			if (amesh->HasTextureCoords(0)) {
+				for (auto idx = f.mIndices; const auto fheh : mesh.fh_range(fh)) {
+					const auto ouv = !amesh->mTextureCoords[0][*idx++];
+					const auto uv = glm::mix(tfc[0], tfc[2], ouv);
+					mesh.set_texcoord2D(fheh, uv);
+				}
+			}
+		}
+	}
+};
+
+void
+AssImp::postLoad()
+{
+	ScemeCPtr scene {
+			aiImportFile(Resource::mapPath(path).c_str(), aiProcess_RemoveRedundantMaterials), &aiReleaseImport};
+	if (!scene) {
+		throw std::runtime_error("Failed to load asset library: " + path);
+	}
+	if (auto mf = Persistence::ParseBase::getShared<AssetFactory>("assetFactory")) {
+		const auto root = AIRANGE(scene->mRootNode, Children);
+		std::transform(
+				root.begin(), root.end(), std::inserter(mf->shapes, mf->shapes.end()), [&scene](const aiNode * m) {
+					return AssetFactory::Shapes::value_type {m->mName.C_Str(), std::make_shared<AssImpNode>(scene, m)};
+				});
+		const auto textures = AIRANGE(scene, Textures);
+		std::transform(textures.begin(), textures.end(),
+				std::inserter(mf->textureFragments, mf->textureFragments.end()), [](const aiTexture * t) {
+					auto texture = std::make_shared<TextureFragment>();
+					texture->id = texture->path = t->mFilename.C_Str();
+					texture->image = std::make_unique<Image>(
+							std::span {reinterpret_cast<unsigned char *>(t->pcData), t->mWidth}, STBI_rgb_alpha);
+					return AssetFactory::TextureFragments::value_type {texture->id, texture};
+				});
+	}
+}
+
+bool
+AssImp::persist(Persistence::PersistenceStore & store)
+{
+	return STORE_TYPE && STORE_MEMBER(path);
+}
-- 
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