OpenGL模型加载篇--模型--17

参考：这里

这一节主要封装模型类：用来加载各种格式的模型。

#ifndef MODEL_H
#define MODEL_H

#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 <string>
#include <fstream>
#include <sstream>
#include <iostream>
#include <map>
#include <vector>
using namespace std;

unsigned int TextureFromFile(const char *path, const string &directory, bool gamma = false);

class Model 
{
public:
    // model data 
    vector<Texture> textures_loaded;	// stores all the textures loaded so far, optimization to make sure textures aren't loaded more than once.
    vector<Mesh>    meshes;
    string directory;
    bool gammaCorrection;

    // constructor, expects a filepath to a 3D model.
    Model(string const &path, bool gamma = false) : gammaCorrection(gamma)
    {
        loadModel(path);
    }

    // draws the model, and thus all its meshes
    void Draw(Shader &shader)
    {
        for(unsigned int i = 0; i < meshes.size(); i++)
            meshes[i].Draw(shader);
    }
    
private:
    // loads a model with supported ASSIMP extensions from file and stores the resulting meshes in the meshes vector.
    void loadModel(string const &path)
    {
        // read file via ASSIMP
        Assimp::Importer importer;
        const aiScene* scene = importer.ReadFile(path, aiProcess_Triangulate | aiProcess_GenSmoothNormals | aiProcess_FlipUVs | aiProcess_CalcTangentSpace);
        // check for errors
        if(!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode) // if is Not Zero
        {
            cout << "ERROR::ASSIMP:: " << importer.GetErrorString() << endl;
            return;
        }
        // retrieve the directory path of the filepath
        directory = path.substr(0, path.find_last_of('/'));

        // process ASSIMP's root node recursively
        processNode(scene->mRootNode, scene);
    }

    // processes a node in a recursive fashion. Processes each individual mesh located at the node and repeats this process on its children nodes (if any).
    void processNode(aiNode *node, const aiScene *scene)
    {
        // process each mesh located at the current node
        for(unsigned int i = 0; i < node->mNumMeshes; i++)
        {
            // the node object only contains indices to index the actual objects in the scene. 
            // the scene contains all the data, node is just to keep stuff organized (like relations between nodes).
            aiMesh* mesh = scene->mMeshes[node->mMeshes[i]];
            meshes.push_back(processMesh(mesh, scene));
        }
        // after we've processed all of the meshes (if any) we then recursively process each of the children nodes
        for(unsigned int i = 0; i < node->mNumChildren; i++)
        {
            processNode(node->mChildren[i], scene);
        }

    }

    Mesh processMesh(aiMesh *mesh, const aiScene *scene)
    {
        // data to fill
        vector<Vertex> vertices;
        vector<unsigned int> indices;
        vector<Texture> textures;

        // walk through each of the mesh's vertices
        for(unsigned int i = 0; i < mesh->mNumVertices; i++)
        {
            Vertex vertex;
            glm::vec3 vector; // we declare a placeholder vector since assimp uses its own vector class that doesn't directly convert to glm's vec3 class so we transfer the data to this placeholder glm::vec3 first.
            // positions
            vector.x = mesh->mVertices[i].x;
            vector.y = mesh->mVertices[i].y;
            vector.z = mesh->mVertices[i].z;
            vertex.Position = vector;
            // normals
            if (mesh->HasNormals())
            {
                vector.x = mesh->mNormals[i].x;
                vector.y = mesh->mNormals[i].y;
                vector.z = mesh->mNormals[i].z;
                vertex.Normal = vector;
            }
            // texture coordinates
            if(mesh->mTextureCoords[0]) // does the mesh contain texture coordinates?
            {
                glm::vec2 vec;
                // a vertex can contain up to 8 different texture coordinates. We thus make the assumption that we won't 
                // use models where a vertex can have multiple texture coordinates so we always take the first set (0).
                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);
        }
        // now wak through each of the mesh's faces (a face is a mesh its triangle) and retrieve the corresponding vertex indices.
        for(unsigned int i = 0; i < mesh->mNumFaces; i++)
        {
            aiFace face = mesh->mFaces[i];
            // retrieve all indices of the face and store them in the indices vector
            for(unsigned int j = 0; j < face.mNumIndices; j++)
                indices.push_back(face.mIndices[j]);        
        }
        // process materials
        aiMaterial* material = scene->mMaterials[mesh->mMaterialIndex];    
        // we assume a convention for sampler names in the shaders. Each diffuse texture should be named
        // as 'texture_diffuseN' where N is a sequential number ranging from 1 to MAX_SAMPLER_NUMBER. 
        // Same applies to other texture as the following list summarizes:
        // diffuse: texture_diffuseN
        // specular: texture_specularN
        // normal: texture_normalN

        // 1. diffuse maps
        vector<Texture> diffuseMaps = loadMaterialTextures(material, aiTextureType_DIFFUSE, "texture_diffuse");
        textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end());
        // 2. specular maps
        vector<Texture> specularMaps = loadMaterialTextures(material, aiTextureType_SPECULAR, "texture_specular");
        textures.insert(textures.end(), specularMaps.begin(), specularMaps.end());
        // 3. normal maps
        std::vector<Texture> normalMaps = loadMaterialTextures(material, aiTextureType_HEIGHT, "texture_normal");
        textures.insert(textures.end(), normalMaps.begin(), normalMaps.end());
        // 4. height maps
        std::vector<Texture> heightMaps = loadMaterialTextures(material, aiTextureType_AMBIENT, "texture_height");
        textures.insert(textures.end(), heightMaps.begin(), heightMaps.end());
        
        // return a mesh object created from the extracted mesh data
        return Mesh(vertices, indices, textures);
    }

    // checks all material textures of a given type and loads the textures if they're not loaded yet.
    // the required info is returned as a Texture struct.
    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);
            // check if texture was loaded before and if so, continue to next iteration: skip loading a new texture
            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; // a texture with the same filepath has already been loaded, continue to next one. (optimization)
                    break;
                }
            }
            if(!skip)
            {   // if texture hasn't been loaded already, load it
                Texture texture;
                texture.id = TextureFromFile(str.C_Str(), this->directory);
                texture.type = typeName;
                texture.path = str.C_Str();
                textures.push_back(texture);
                textures_loaded.push_back(texture);  // store it as texture loaded for entire model, to ensure we won't unnecesery load duplicate textures.
            }
        }
        return textures;
    }
};


unsigned int TextureFromFile(const char *path, const string &directory, bool gamma)
{
    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;
}
#endif

程序代码：就比较简单了，直接利用Model类加载和绘制。
Model类只设置漫反射和高光贴图，而且shader里的名字要和Model里设置的对应。
一些其他的uniform变量还需我们自己设置。

//顺序不能错
#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 <learnopengl/Shader.h>
#include <learnopengl/Camera.h>
#include <learnopengl/Model.h>

#include <iostream>

using namespace std;

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow* window);
void mouse_callback(GLFWwindow* window, double x, double y);
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
unsigned int loadTexture(const char* path);

const int SCR_WIDTH = 800;
const int SCR_HEIGHT = 600;

Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = SCR_WIDTH / 2, lastY = SCR_WIDTH / 2;
bool firstMouse = true;

float deltaTime = 0.0f;
float lastFrame = 0.0f;

glm::vec3 lightPos(1.2f, 1.0f, 2.0f);

int main()
{
	//Init
	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

	GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "hahaha", NULL, NULL);
	if (window == NULL)
	{
		cout << "Failed to create GLFW window !" << endl;
		glfwTerminate();
		return -1;
	}

	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
	glfwSetCursorPosCallback(window, mouse_callback);
	glfwSetScrollCallback(window, scroll_callback);

	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		cout << "Failed to init GLAD !" << endl;
	}

	//configure
	glEnable(GL_DEPTH_TEST);	
	
	//反转贴图Y轴：如果模型贴图Y轴显示颠倒，需要反转
	//stbi_set_flip_vertically_on_load(true);
	
	//隐藏光标
	glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

	//build and compile shader
	Shader shader("Shaders/Learn17.vs", "Shaders/Learn17.fs");

	Model ourModel("Models/1/nanosuit.obj");

	//render loop
	while (!glfwWindowShouldClose(window))
	{
		float currentFrame = glfwGetTime();
		deltaTime = currentFrame - lastFrame;
		lastFrame = currentFrame;

		//input
		processInput(window);

		//render
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		shader.use();
		shader.setVec3("viewPos", camera.Position);
		//绕Y轴旋转
		shader.setVec3("dirLight.direction", glm::vec3(sin(glfwGetTime()*5),0.0f, cos(glfwGetTime() * 5)));
		shader.setVec3("dirLight.ambient", 1.0f, 1.0f, 1.0f);
		shader.setVec3("dirLight.diffuse", 1.0f, 1.0f, 1.0f);
		shader.setVec3("dirLight.specular", 1.0f, 1.0f, 0.0f);
		shader.setFloat("material.shininess", 32);

		glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
		glm::mat4 view = camera.GetViewMatrix();
		shader.setMat4("projection", projection);
		shader.setMat4("view", view);

		glm::mat4 model = glm::mat4(1.0f);
		model = glm::translate(model, glm::vec3(0.0f, -5.0f, -10.0f));
		model = glm::scale(model, glm::vec3(1.0f, 1.0f, 1.0f));
		shader.setMat4("model", model);

		ourModel.Draw(shader);

		//swap buffer
		glfwSwapBuffers(window);
		//call event
		glfwPollEvents();
	}

	//terminate clearing all previously allocated GLFW resources
	glfwTerminate();
	return 0;
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
	glViewport(0, 0, SCR_WIDTH, SCR_HEIGHT);
}

void processInput(GLFWwindow* window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
	{
		glfwSetWindowShouldClose(window, true);
	}

	if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
		camera.ProcessKeyboard(FORWARD, deltaTime);
	if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
		camera.ProcessKeyboard(BACKWARD, deltaTime);
	if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
		camera.ProcessKeyboard(LEFT, deltaTime);
	if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
		camera.ProcessKeyboard(RIGHT, deltaTime);
}


void mouse_callback(GLFWwindow* window, double x, double y)
{
	if (firstMouse)
	{
		lastX = x;
		lastY = y;
		firstMouse = false;
	}

	float xoffset = x - lastX;
	float yoffset = lastY - y;

	lastX = x;
	lastY = y;

	camera.ProcessMouseMovement(xoffset, yoffset);
}



void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
	camera.ProcessMouseScroll(yoffset);
}

unsigned int loadTexture(const char* path)
{
	unsigned int textureID;
	glGenTextures(1, &textureID);
	glBindTexture(GL_TEXTURE_2D, textureID);
	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);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	//load
	int width, height, channels;
	auto data = stbi_load(path, &width, &height, &channels, 0);
	if (data)
	{
		//根据通道数判断图片格式
		GLenum format;
		if (channels == 1)
			format = GL_RED;
		if (channels == 3)
			format = GL_RGB;
		if (channels == 4)
			format = GL_RGBA;

		glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
		glGenerateMipmap(GL_TEXTURE_2D);
	}
	else
	{
		cout << "failed to load texture!" << path << endl;
	}
	stbi_image_free(data);

	return textureID;
}

顶点着色器：

#version 330 core
layout(location=0)in vec3 aPos;
layout(location=1)in vec3 aNormal;
layout(location=2)in vec2 aTexcoord;

out vec3 normal;
out vec3 fragPos;
out vec2 uv;

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;
	uv=aTexcoord;
}

片元着色器：

#version 330 core
out vec4 fragColor;

struct Material
{	 
	sampler2D texture_diffuse1;
	sampler2D texture_specular1;	
	float shininess;
};

//定向光
struct DirLight
{	
	vec3 direction;	
	
	vec3 ambient;
	vec3 diffuse;
	vec3 specular;
};

uniform Material material;
uniform DirLight dirLight;

in vec2 uv;
in vec3 normal;
in vec3 fragPos;

uniform vec3 viewPos;

vec3 CalcDirLight(DirLight light,vec3 normal,vec3 viewDir)
{
	vec3 lightDir=normalize(-light.direction);
	
	//环境光
	vec3 ambient=light.ambient* vec3(texture(material.texture_diffuse1,uv));
	
	//漫反射
	float dif=max(dot(normal,lightDir),0.0);
	vec3 diffuse=light.diffuse*dif*vec3(texture(material.texture_diffuse1,uv));
	
	//高光
	vec3 reflectDir=reflect(-lightDir,normal);
	float spe=pow(max(dot(reflectDir,viewDir),0.0),material.shininess);
	vec3 specular=light.specular*spe*vec3(texture(material.texture_specular1,uv));
	
	return ambient+diffuse+specular;
}


void main()
{	
	vec3 worldNormal=normalize(normal);	
	vec3 viewDir=normalize(viewPos-fragPos);	
	
	//定向光
	vec3 result=CalcDirLight(dirLight,worldNormal,viewDir);

	fragColor=vec4(result,1.0);
}

最后

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