本人刚学OpenGL不久且自学，文中定有代码、术语等错误，欢迎指正
我写的项目地址：https://github.com/liujianjie/LearnOpenGLProject
模型加载重要代码
这点需结合代码全部才好理解，可以跳过此点直接看程序代码
读取3D模型
Assimp::Importer importer;
const aiScene *scene = importer.ReadFile(path, aiProcess_Triangulate | aiProcess_FlipUVs);
ReadFile的第二个参数是一些后期处理(Post-processing)的选项
- aiProcess_Triangulate:如果模型不是（全部）由三角形组成，它需要将模型所有的图元形状变换为三角形
- aiProcess_FlipUVs:在处理的时候翻转y轴的纹理坐标
- aiProcess_GenNormals：如果模型不包含法向量的话，就为每个顶点创建法线。
- aiProcess_SplitLargeMeshes：将比较大的网格分割成更小的子网格，如果你的渲染有最大顶点数限制，只能渲染较小的网格，那么它会非常有用。
- aiProcess_OptimizeMeshes：和上个选项相反，它会将多个小网格拼接为一个大的网格，减少绘制调用从而进行优化。
递归处理结点的网格
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代码
void processNode(aiNode *node, const aiScene *scene) { // 处理节点所有的网格（如果有的话） for(unsigned int i = 0; i < node->mNumMeshes; i++) { aiMesh *mesh = scene->mMeshes[node->mMeshes[i]]; meshes.push_back(processMesh(mesh, scene)); } // 递归接下来对它的子节点重复这一过程 for(unsigned int i = 0; i < node->mNumChildren; i++) { processNode(node->mChildren[i], scene); } } -
说明
本可以不用递归处理任何节点，渲染时只需要遍历场景对象的所有网格即可
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为什么要递归处理网格
使用节点的最初想法是将网格之间定义一个父子关系。通过这样递归地遍历这层关系，我们就能将某个网格定义为另一个网格的父网格了。
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例子
位移一个汽车的网格时，你可以保证它的所有子网格（比如引擎网格、方向盘网格、轮胎网格）都会随着一起位移。这样的系统能够用父子关系很容易地实现。
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加载纹理优化
大多数场景都会在多个网格中重用部分纹理，所以不需要每次加载网格用的纹理，应该存储到vector中判断是否加载过，是加载过就只需将加载过的纹理放到vector的后面就行
vector<Texture> loadMaterialTextures(aiMaterial *mat, aiTextureType type, string typeName)
{
vector<Texture> textures;
for(unsigned int i = 0; i < mat->GetTextureCount(type); i++)
{
aiString str;
mat->GetTexture(type, i, &str);
bool skip = false;
for(unsigned int j = 0; j < textures_loaded.size(); j++)
{
if(std::strcmp(textures_loaded[j].path.data(), str.C_Str()) == 0)
{
textures.push_back(textures_loaded[j]);
skip = true;
break;
}
}
if(!skip)
{
// 如果纹理还没有被加载，则加载它
Texture texture;
texture.id = TextureFromFile(str.C_Str(), directory);
texture.type = typeName;
texture.path = str.C_Str();
textures.push_back(texture);
textures_loaded.push_back(texture); // 添加到已加载的纹理中
}
}
return textures;
}
程序代码
Model类加载模型流程
例子1：渲染模型
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代码
model.h
#pragma once #include <glad/glad.h> #include <glm/glm.hpp> #include <glm/gtc/matrix_transform.hpp> #include <stb_image.h> #include <assimp/Importer.hpp> #include <assimp/scene.h> #include <assimp/postprocess.h> //#include <learnopengl/mesh.h> //#include <learnopengl/shader.h> #include "Mesh.h" #include "Core/Shader/Shader.h" #include <string> #include <fstream> #include <sstream> #include <iostream> #include <map> #include <vector> using namespace std; // 辅助方法：从路径中加载材质 //unsigned int TextureFromFile(const char* path, const string& directory, bool gamma = false); unsigned int TextureFromFile(const char* path, const string& directory, bool gamma = false) { string filename = string(path); filename = directory + '/' + filename; unsigned int textureID; glGenTextures(1, &textureID); int width, height, nrComponents; unsigned char* data = stbi_load(filename.c_str(), &width, &height, &nrComponents, 0); if (data) { GLenum format; if (nrComponents == 1) format = GL_RED; else if (nrComponents == 3) format = GL_RGB; else if (nrComponents == 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 << "Texture failed to load at path: " << path << std::endl; stbi_image_free(data); } return textureID; } class Model { public: vector<Texture> textures_loaded; vector<Mesh> meshes; string directory; bool gammaCorrection; // 构造函数 Model(string const& path, bool gamma = false) : gammaCorrection(gamma) { loadModel(path); } // 绘画 void Draw(Shader& shader) { for (unsigned int i = 0; i < meshes.size(); i++) { meshes[i].Draw(shader); } } private: // 加载模型 void loadModel(string const &path) { 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) { cout << "ERROR::ASSIMP:: " << importer.GetErrorString() << endl; return; } directory = path.substr(0, path.find_last_of("/"));// 保存目录 // 处理结点 processNode(scene->mRootNode, scene); } /// <summary> /// 递归处理结点下的网格，处理完网格就新建一个自定义的mesh类并添加到vector中存储所有网格 /// </summary> /// <param name="node">根结点，递归过程中变成子结点</param> /// <param name="scene">场景</param> void processNode(aiNode* node, const aiScene* scene) { // 处理当前结点下的每一个网格 for (unsigned int i = 0; i < node->mNumMeshes; i++) { aiMesh* mesh = scene->mMeshes[node->mMeshes[i]];// 在scene哪个网格 meshes.push_back(processMesh(mesh, scene));// 处理网格后，保存为我们自己的类 } // 递归处理子节点 for (unsigned int i = 0; i < node->mNumChildren; i++) { processNode(node->mChildren[i], scene); } } /// <summary> /// 处理结点下的网格，读取绘制网格所需的顶点、法线、贴图 /// </summary> /// <param name="mesh">具体的网格数据</param> /// <param name="scene">哪个场景下</param> /// <returns>返回自定义mesh类</returns> Mesh processMesh(aiMesh* mesh, const aiScene* scene) { vector<Vertex> vertices; vector<unsigned int> indices; 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; if (mesh->HasNormals()) { 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 vec; vec.x = mesh->mTextureCoords[0][i].x; vec.y = mesh->mTextureCoords[0][i].y; vertex.TexCoords = vec; // 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.TexCoords = glm::vec2(0.0f, 0.0f); } vertices.push_back(vertex); } // 网格下有众多面，面的绘制索引存储起来 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]); } } aiMaterial* material = scene->mMaterials[mesh->mMaterialIndex]; // 1.漫反射贴图 vector<Texture> diffuseMaps = loadMaterialTextures(material, aiTextureType_DIFFUSE, "texture_diffuse"); textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end()); // 2.镜面光贴图 vector<Texture> specularMaps = loadMaterialTextures(material, aiTextureType_SPECULAR, "texture_specular"); textures.insert(textures.end(), specularMaps.begin(), specularMaps.end()); // 3.法线贴图 vector<Texture> normalMaps = loadMaterialTextures(material, aiTextureType_HEIGHT, "texture_normal"); textures.insert(textures.end(), normalMaps.begin(), normalMaps.end()); // 4.高度图 vector<Texture> heightMaps = loadMaterialTextures(material, aiTextureType_AMBIENT, "texture_height"); textures.insert(textures.end(), heightMaps.begin(), heightMaps.end()); return Mesh(vertices, indices, textures); } /// <summary> /// 处理网格的辅助方法：加载一个网格下对应的类型贴图 /// </summary> /// <param name="mat">场景下网格对应的材质</param> /// <param name="type">材质类型</param> /// <param name="typeName">自定义格式名</param> /// <returns>返回这个网格下，对应材质类型的材质</returns> vector<Texture> loadMaterialTextures(aiMaterial* mat, aiTextureType type, string typeName) { vector<Texture> textures; for (unsigned int i = 0; i < mat->GetTextureCount(type); i++) { aiString str; mat->GetTexture(type, i, &str); bool skip = false; for (unsigned int j = 0; j < textures_loaded.size(); j++) { // 加载过 if (std::strcmp(textures_loaded[j].path.data(), str.C_Str()) == 0) { textures.push_back(textures_loaded[i]);// 放在后面 skip = true; break; } } if (!skip) { Texture texture; texture.id = TextureFromFile(str.C_Str(), this->directory); texture.type = typeName; texture.path = str.C_Str(); textures.push_back(texture); // 未知也要增加 textures_loaded.push_back(texture);// 添加到已知 } } return textures; } };cpp
#include <glad/glad.h> #include <GLFW/glfw3.h> #include <stb_image.h> #include <glm/glm.hpp> #include <glm/gtc/matrix_transform.hpp> #include <glm/gtc/type_ptr.hpp> #include "Core/Shader/Shader.h" #include "Core/Camera/Camera.h" #include "Core/LoadModel/Model.h" #include <iostream> #include "MyFileSystem.h" void framebuffer_size_callback(GLFWwindow* window, int width, int height); void mouse_callback(GLFWwindow* window, double xpos, double ypos); void scroll_callback(GLFWwindow* window, double xoffset, double yoffset); void processInput(GLFWwindow* window); unsigned int loadTexture(const char* path); // settings const unsigned int SCR_WIDTH = 1920; const unsigned int SCR_HEIGHT = 1080; // camera Camera camera(glm::vec3(0.0f, 0.0f, 3.0f)); float lastX = SCR_WIDTH / 2.0f; float lastY = SCR_HEIGHT / 2.0f; bool firstMouse = true; // timing float deltaTime = 0.0f; float lastFrame = 0.0f; // lighting glm::vec3 lightPos(1.2f, 1.0f, 2.0f); int main() { // glfw: initialize and configure // ------------------------------ glfwInit(); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); #ifdef __APPLE__ glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); #endif // glfw window creation // -------------------- GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL); if (window == NULL) { std::cout << "Failed to create GLFW window" << std::endl; glfwTerminate(); return -1; } glfwMakeContextCurrent(window); glfwSetFramebufferSizeCallback(window, framebuffer_size_callback); glfwSetCursorPosCallback(window, mouse_callback); glfwSetScrollCallback(window, scroll_callback); // tell GLFW to capture our mouse glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED); // glad: load all OpenGL function pointers // --------------------------------------- if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) { std::cout << "Failed to initialize GLAD" << std::endl; return -1; } // configure global opengl state // ----------------------------- glEnable(GL_DEPTH_TEST); // build and compile our shader zprogram // ------------------------------------ //Shader lightingShader("1.colors.vs", "1.colors.fs"); // 物体的光照shader Shader ourShader("assest/shader/3模型/3.1.模型加载.vs", "assest/shader/3模型/3.1.模型加载.fs"); // 加载模型 Model ourModel(FileSystem::getPath("assest/model/nanosuit/nanosuit.obj")); // render loop // ----------- while (!glfwWindowShouldClose(window)) { // per-frame time logic // -------------------- float currentFrame = static_cast<float>(glfwGetTime()); deltaTime = currentFrame - lastFrame; lastFrame = currentFrame; // input // ----- processInput(window); // render // ------ glClearColor(0.1f, 0.1f, 0.1f, 1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // be sure to activate shader when setting uniforms/drawing objects ourShader.use(); // view/projection transformations glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); glm::mat4 view = camera.GetViewMatrix(); ourShader.setMat4("projection", projection); ourShader.setMat4("view", view); // 渲染这个模型 glm::mat4 model = glm::mat4(1.0f); model = glm::translate(model, glm::vec3(0.0f, 0.0f, 0.0f)); model = glm::scale(model, glm::vec3(1.0f, 1.0f, 1.0f)); ourShader.setMat4("model", model); ourModel.Draw(ourShader); // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.) // ------------------------------------------------------------------------------- glfwSwapBuffers(window); glfwPollEvents(); } // glfw: terminate, clearing all previously allocated GLFW resources. // ------------------------------------------------------------------ glfwTerminate(); return 0; } ....glsl
#version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec3 aNormal; layout (location = 2) in vec2 aTexCoords; out vec2 TexCoords; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { TexCoords = aTexCoords; gl_Position = projection * view * model * vec4(aPos, 1.0); }#version 330 core out vec4 FragColor; in vec2 TexCoords; uniform sampler2D texture_diffuse1; void main(){ FragColor = texture(texture_diffuse1, TexCoords); } -
效果
例子2：添加点光源
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代码
#version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec3 aNormal; layout (location = 2) in vec2 aTexCoords; out vec3 FragPos; out vec3 Normal; out vec2 TexCoords; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { gl_Position = projection * view * model * vec4(aPos, 1.0); FragPos = vec3(model * vec4(aPos, 1.0)); Normal = mat3(transpose(inverse(model))) * aNormal; TexCoords = aTexCoords; }#version 330 core out vec4 FragColor; in vec3 FragPos; in vec3 Normal; in vec2 TexCoords;// 纹理坐标 uniform vec3 viewPos; uniform sampler2D texture_diffuse1;// 纹理单元 uniform sampler2D texture_specular1;// 纹理单元 // 点光源 struct PointLight { vec3 position; vec3 ambient; vec3 diffuse; vec3 specular; float constant; // 常数 float linear; // 一次项 float quadratic;// 二次项 }; #define NR_POINT_LIGHTS 2 uniform PointLight pointLights[NR_POINT_LIGHTS]; // 计算点光源影响当前片段的颜色 vec3 CalcPointLight(PointLight light, vec3 normal, vec3 fragPos, vec3 viewDir){ vec3 lightDir = normalize(light.position - fragPos); // 漫反射光照分量 float diff = max(dot(normal, lightDir), 0.0); // 镜面光光照分量 vec3 reflectDir = reflect(-lightDir, normal); float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32); // 衰减 float distance = length(light.position - fragPos); float attenuation = 1.0 / (light.constant + light.linear * distance + light.quadratic * distance * distance); // 合并结果 vec3 ambient = light.ambient * vec3(texture(texture_diffuse1, TexCoords)); vec3 diffuse = light.diffuse * diff * vec3(texture(texture_diffuse1, TexCoords)); vec3 specular = light.specular * spec * vec3(texture(texture_specular1, TexCoords)); ambient *= attenuation; diffuse *= attenuation; specular *= attenuation; return (ambient + diffuse + specular); } void main(){ // 属性 vec3 norm = normalize(Normal); vec3 viewDir = normalize(viewPos - FragPos); vec3 result; // 点光源 for(int i = 0; i < NR_POINT_LIGHTS; i++){ result += CalcPointLight(pointLights[i], norm, FragPos, viewDir); } //vec4 diffuse = texture(texture_diffuse1, TexCoords); //vec4 specular = texture(texture_specular1, TexCoords); FragColor = vec4(result, 1.0); }// 点光源 ourShader.use(); ourShader.setVec3("pointLights[0].position", pointLightPositions[0]); ourShader.setVec3("pointLights[0].ambient", 0.4f, 0.4f, 0.4f); ourShader.setVec3("pointLights[0].diffuse", 0.8f, 0.8f, 0.8f); ourShader.setVec3("pointLights[0].specular", 1.0f, 1.0f, 1.0f); ourShader.setFloat("pointLights[0].constant", 1.0f); ourShader.setFloat("pointLights[0].linear", 0.09f); ourShader.setFloat("pointLights[0].quadratic", 0.032f); ourShader.setVec3("pointLights[1].position", pointLightPositions[1]); ourShader.setVec3("pointLights[1].ambient", 0.4f, 0.4f, 0.4f); ourShader.setVec3("pointLights[1].diffuse", 0.8f, 0.8f, 0.8f); ourShader.setVec3("pointLights[1].specular", 1.0f, 1.0f, 1.0f); ourShader.setFloat("pointLights[1].constant", 1.0f); ourShader.setFloat("pointLights[1].linear", 0.09f); ourShader.setFloat("pointLights[1].quadratic", 0.032f); while (!glfwWindowShouldClose(window)) { ourShader.use(); ourShader.setVec3("viewPos", camera.Position); // view/projection transformations glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); glm::mat4 view = camera.GetViewMatrix(); ourShader.setMat4("projection", projection); ourShader.setMat4("view", view); // 渲染这个模型 glm::mat4 model = glm::mat4(1.0f); model = glm::translate(model, glm::vec3(0.0f, 0.0f, 0.0f)); model = glm::scale(model, glm::vec3(0.1f, 0.1f, 0.1f)); ourShader.setMat4("model", model); ourModel.Draw(ourShader); ...... // 上一节自定义mesh写的函数 void Draw(Shader& shader) { // 绑定适合的纹理 unsigned int diffuseNr = 1; unsigned int specularNr = 1; unsigned int normalNr = 1; unsigned int heightNr = 1; for (unsigned int i = 0; i < textures.size(); i++) { glActiveTexture(GL_TEXTURE0 + i); string number; string name = textures[i].type; if (name == "texture_diffuse") { number = std::to_string(diffuseNr++); }else if (name == "texture_specular") { number = std::to_string(specularNr++); }else if (name == "texture_normal") { number = std::to_string(normalNr++); }else if (name == "texture_height") { number = std::to_string(heightNr++); } // 给shader的采样器设置纹理单元 glUniform1i(glGetUniformLocation(shader.ID, (name + number).c_str()), i); glBindTexture(GL_TEXTURE_2D, textures[i].id); } // 绘画 glBindVertexArray(VAO); glDrawElements(GL_TRIANGLES, static_cast<unsigned int>(indices.size()), GL_UNSIGNED_INT, 0); // 绘画完设为默认值 glActiveTexture(GL_TEXTURE0); } -
效果
