model.cpp

#include "model.hpp"

#include <assimp/Importer.hpp>
#include <assimp/scene.h>
#include <assimp/postprocess.h>

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

Model::Model(const char* path) {
	LoadModel(path);
}

void Model::Draw(Shader& shader) {
	for (unsigned int i = 0; i < meshes.size(); i++) {
		meshes[i].Draw(shader);
	}
}

void Model::LoadModel(string path) {
	stbi_set_flip_vertically_on_load(true);

	Assimp::Importer importer;
	const aiScene* scene = importer.ReadFile(path, aiProcess_Triangulate | aiProcess_GenSmoothNormals | aiProcess_FlipUVs | aiProcess_CalcTangentSpace);

	if (!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode) {
		std::cout << "ERROR::ASSIMP::" << importer.GetErrorString() << std::endl;
		return;
	}

	directory = path.substr(0, path.find_last_of('/'));
	ProcessNode(scene->mRootNode, scene);
}

void Model::ProcessNode(aiNode* node, const aiScene* scene) {
	for (unsigned int i = 0; i < node->mNumMeshes; i++) {
		aiMesh* mesh = scene->mMeshes[node->mMeshes[i]];
		meshes.push_back(ProcessMesh(mesh, scene));
	}

	for (unsigned int i = 0; i < node->mNumChildren; i++) {
		ProcessNode(node->mChildren[i], scene);
	}
}

Mesh Model::ProcessMesh(aiMesh* mesh, const aiScene* scene) {
	std::vector<Vertex> vertices;
	std::vector<unsigned int> indices;
	std::vector<Texture> textures;

	for (unsigned int i = 0; i < mesh->mNumVertices; i++) {
		Vertex vertex;
		
		glm::vec3 vector;
		vector.x = mesh->mVertices[i].x;
		vector.y = mesh->mVertices[i].y;
		vector.z = mesh->mVertices[i].z;
		vertex.position = vector;

		vector.x = mesh->mNormals[i].x;
		vector.y = mesh->mNormals[i].y;
		vector.z = mesh->mNormals[i].z;
		vertex.normal = vector;

		if (mesh->mTextureCoords[0]) {
			glm::vec2 texCoords;
			texCoords.x = mesh->mTextureCoords[0][i].x;
			texCoords.y = mesh->mTextureCoords[0][i].y;
			vertex.textureCoordinates = texCoords;

			// tangent
			vector.x = mesh->mTangents[i].x;
			vector.y = mesh->mTangents[i].y;
			vector.z = mesh->mTangents[i].z;
			vertex.Tangent = vector;

			// bitangent
			vector.x = mesh->mBitangents[i].x;
			vector.y = mesh->mBitangents[i].y;
			vector.z = mesh->mBitangents[i].z;
			vertex.Bitangent = vector;

		} else {
			vertex.textureCoordinates = glm::vec2(0.0f);
		}

		vertices.push_back(vertex);
	}

	for (unsigned int i = 0; i < mesh->mNumFaces; i++) {
		aiFace face = mesh->mFaces[i];
		for (unsigned int j = 0; j < face.mNumIndices; j++) {
			indices.push_back(face.mIndices[j]);
		}
	}

	if (mesh->mMaterialIndex >= 0) {
		aiMaterial* material = scene->mMaterials[mesh->mMaterialIndex];
		std::vector<Texture> diffuseMaps = LoadMaterialTextures(material, aiTextureType_DIFFUSE, "texture_diffuse");
		std::vector<Texture> specularMaps = LoadMaterialTextures(material, aiTextureType_SPECULAR, "texture_specular");
		std::vector<Texture> normalMaps = LoadMaterialTextures(material, aiTextureType_HEIGHT, "texture_normal");
		std::vector<Texture> heightMaps = LoadMaterialTextures(material, aiTextureType_AMBIENT, "texture_height");

		textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end());
		textures.insert(textures.end(), specularMaps.begin(), specularMaps.end());
		textures.insert(textures.end(), normalMaps.begin(), normalMaps.end());
		textures.insert(textures.end(), heightMaps.begin(), heightMaps.end());
	}

	return Mesh(vertices, indices, textures);
}

vector<Texture> Model::LoadMaterialTextures(aiMaterial* mat, aiTextureType type, string typeName) {
	std::vector<Texture> textures;

	for (unsigned int i = 0; i < mat->GetTextureCount(type); i++) {
		aiString filepath;
		mat->GetTexture(type, i, &filepath);

		bool alreadyLoaded = false;
		for (unsigned int j = 0; j < texturesLoaded.size(); j++) {
			if (std::strcmp(texturesLoaded[j].path.data(), filepath.C_Str()) == 0) {
				textures.push_back(texturesLoaded[j]);
				alreadyLoaded = true;
				break;
			}
		}

		if (!alreadyLoaded) {
			Texture texture;
			texture.id = TextureFromFile(filepath.C_Str(), this->directory);
			texture.type = typeName;
			texture.path = filepath.C_Str();
			textures.push_back(texture);
			texturesLoaded.push_back(texture);
		}
	}

	return textures;
}


unsigned int Model::TextureFromFile(const char* path, const string& directory, bool gamma) {
	string filename = string(path);
	filename = directory + "/" + filename;

	GLuint textureID;
	glGenTextures(1, &textureID);
	
	int width, height, nrChannels;
	unsigned char* data = stbi_load(filename.c_str(), &width, &height, &nrChannels, 0);

	if (data) {
		GLenum format = GL_RED;

		if (nrChannels == 3)
			format = GL_RGB;
		else if (nrChannels == 4)
			format = GL_RGBA;

		glBindTexture(GL_TEXTURE_2D, textureID);
		glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
		glGenerateMipmap(GL_TEXTURE_2D);

		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

		stbi_image_free(data);

	} else {
		std::cout << "Failed to load texture " << filename << std::endl;
		exit(1);
	}

	return textureID;
}