OpenGL学习--08--基本渲染(灯光)

Posted 2020-09-27 ParamousGIS

 

1.tutorial08.cpp

// Include standard headers
#include <stdio.h>
#include <stdlib.h>
#include <vector>

// Include GLEW
#include <GL/glew.h>

// Include GLFW
#include <glfw3.h>
GLFWwindow* window;

// Include GLM
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
using namespace glm;

#include <common/shader.hpp>
#include <common/texture.hpp>
#include <common/controls.hpp>
#include <common/objloader.hpp>
#include <common/vboindexer.hpp>

int main( void )
{
    // Initialise GLFW
    if( !glfwInit() )
    {
        fprintf( stderr, "Failed to initialize GLFW\\n" );
        getchar();
        return -1;
    }

    glfwWindowHint(GLFW_SAMPLES, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make MacOS happy; should not be needed
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    // Open a window and create its OpenGL context
    window = glfwCreateWindow( 1024, 768, "Tutorial 08 - Basic Shading", NULL, NULL);
    if( window == NULL ){
        fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\\n" );
        getchar();
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);

    // Initialize GLEW
    glewExperimental = true; // Needed for core profile
    if (glewInit() != GLEW_OK) {
        fprintf(stderr, "Failed to initialize GLEW\\n");
        getchar();
        glfwTerminate();
        return -1;
    }

    // Ensure we can capture the escape key being pressed below
    glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
    // Hide the mouse and enable unlimited mouvement
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    
    // Set the mouse at the center of the screen
    glfwPollEvents();
    glfwSetCursorPos(window, 1024/2, 768/2);

    // Dark blue background
    glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

    // Enable depth test
    glEnable(GL_DEPTH_TEST);
    // Accept fragment if it closer to the camera than the former one
    glDepthFunc(GL_LESS); 

    // Cull triangles which normal is not towards the camera
    glEnable(GL_CULL_FACE);

    GLuint VertexArrayID;
    glGenVertexArrays(1, &VertexArrayID);
    glBindVertexArray(VertexArrayID);

    // Create and compile our GLSL program from the shaders
    GLuint programID = LoadShaders( "StandardShading.vertexshader", "StandardShading.fragmentshader" );

    // Get a handle for our "MVP" uniform
    GLuint MatrixID = glGetUniformLocation(programID, "MVP");
    GLuint ViewMatrixID = glGetUniformLocation(programID, "V");
    GLuint ModelMatrixID = glGetUniformLocation(programID, "M");

    // Load the texture
    GLuint Texture = loadDDS("uvmap.DDS");
    
    // Get a handle for our "myTextureSampler" uniform
    GLuint TextureID  = glGetUniformLocation(programID, "myTextureSampler");

    // Read our .obj file
    std::vector<glm::vec3> vertices;
    std::vector<glm::vec2> uvs;
    std::vector<glm::vec3> normals;
    bool res = loadOBJ("suzanne.obj", vertices, uvs, normals);

    // Load it into a VBO

    GLuint vertexbuffer;
    glGenBuffers(1, &vertexbuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
    glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(glm::vec3), &vertices[0], GL_STATIC_DRAW);

    GLuint uvbuffer;
    glGenBuffers(1, &uvbuffer);
    glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
    glBufferData(GL_ARRAY_BUFFER, uvs.size() * sizeof(glm::vec2), &uvs[0], GL_STATIC_DRAW);

    GLuint normalbuffer;
    glGenBuffers(1, &normalbuffer);
    glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
    glBufferData(GL_ARRAY_BUFFER, normals.size() * sizeof(glm::vec3), &normals[0], GL_STATIC_DRAW);

    // Get a handle for our "LightPosition" uniform
    glUseProgram(programID);
    GLuint LightID = glGetUniformLocation(programID, "LightPosition_worldspace");

    do{

        // Clear the screen
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        // Use our shader
        glUseProgram(programID);

        // Compute the MVP matrix from keyboard and mouse input
        computeMatricesFromInputs();
        glm::mat4 ProjectionMatrix = getProjectionMatrix();
        glm::mat4 ViewMatrix = getViewMatrix();
        glm::mat4 ModelMatrix = glm::mat4(1.0);
        glm::mat4 MVP = ProjectionMatrix * ViewMatrix * ModelMatrix;

        // Send our transformation to the currently bound shader, 
        // in the "MVP" uniform
        glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
        glUniformMatrix4fv(ModelMatrixID, 1, GL_FALSE, &ModelMatrix[0][0]);
        glUniformMatrix4fv(ViewMatrixID, 1, GL_FALSE, &ViewMatrix[0][0]);

        glm::vec3 lightPos = glm::vec3(4,4,4);
        glUniform3f(LightID, lightPos.x, lightPos.y, lightPos.z);

        // Bind our texture in Texture Unit 0
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, Texture);
        // Set our "myTextureSampler" sampler to user Texture Unit 0
        glUniform1i(TextureID, 0);

        // 1rst attribute buffer : vertices
        glEnableVertexAttribArray(0);
        glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
        glVertexAttribPointer(
            0,                  // attribute
            3,                  // size
            GL_FLOAT,           // type
            GL_FALSE,           // normalized?
            0,                  // stride
            (void*)0            // array buffer offset
        );

        // 2nd attribute buffer : UVs
        glEnableVertexAttribArray(1);
        glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
        glVertexAttribPointer(
            1,                                // attribute
            2,                                // size
            GL_FLOAT,                         // type
            GL_FALSE,                         // normalized?
            0,                                // stride
            (void*)0                          // array buffer offset
        );

        // 3rd attribute buffer : normals
        glEnableVertexAttribArray(2);
        glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
        glVertexAttribPointer(
            2,                                // attribute
            3,                                // size
            GL_FLOAT,                         // type
            GL_FALSE,                         // normalized?
            0,                                // stride
            (void*)0                          // array buffer offset
        );

        // Draw the triangles !
        glDrawArrays(GL_TRIANGLES, 0, vertices.size() );

        glDisableVertexAttribArray(0);
        glDisableVertexAttribArray(1);
        glDisableVertexAttribArray(2);

        // Swap buffers
        glfwSwapBuffers(window);
        glfwPollEvents();

    } // Check if the ESC key was pressed or the window was closed
    while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
           glfwWindowShouldClose(window) == 0 );

    // Cleanup VBO and shader
    glDeleteBuffers(1, &vertexbuffer);
    glDeleteBuffers(1, &uvbuffer);
    glDeleteBuffers(1, &normalbuffer);
    glDeleteProgram(programID);
    glDeleteTextures(1, &Texture);
    glDeleteVertexArrays(1, &VertexArrayID);

    // Close OpenGL window and terminate GLFW
    glfwTerminate();

    return 0;
}

 

2. common/objloader.cpp

#include <vector>
#include <stdio.h>
#include <string>
#include <cstring>

#include <glm/glm.hpp>

#include "objloader.hpp"

// Very, VERY simple OBJ loader.
// Here is a short list of features a real function would provide : 
// - Binary files. Reading a model should be just a few memcpy\'s away, not parsing a file at runtime. In short : OBJ is not very great.
// - Animations & bones (includes bones weights)
// - Multiple UVs
// - All attributes should be optional, not "forced"
// - More stable. Change a line in the OBJ file and it crashes.
// - More secure. Change another line and you can inject code.
// - Loading from memory, stream, etc

bool loadOBJ(
    const char * path, 
    std::vector<glm::vec3> & out_vertices, 
    std::vector<glm::vec2> & out_uvs,
    std::vector<glm::vec3> & out_normals
){
    printf("Loading OBJ file %s...\\n", path);

    std::vector<unsigned int> vertexIndices, uvIndices, normalIndices;
    std::vector<glm::vec3> temp_vertices; 
    std::vector<glm::vec2> temp_uvs;
    std::vector<glm::vec3> temp_normals;


    FILE * file = fopen(path, "r");
    if( file == NULL ){
        printf("Impossible to open the file ! Are you in the right path ? See Tutorial 1 for details\\n");
        getchar();
        return false;
    }

    while( 1 ){

        char lineHeader[128];
        // read the first word of the line
        int res = fscanf(file, "%s", lineHeader);
        if (res == EOF)
            break; // EOF = End Of File. Quit the loop.

        // else : parse lineHeader
        
        if ( strcmp( lineHeader, "v" ) == 0 ){
            glm::vec3 vertex;
            fscanf(file, "%f %f %f\\n", &vertex.x, &vertex.y, &vertex.z );
            temp_vertices.push_back(vertex);
        }else if ( strcmp( lineHeader, "vt" ) == 0 ){
            glm::vec2 uv;
            fscanf(file, "%f %f\\n", &uv.x, &uv.y );
            uv.y = -uv.y; // Invert V coordinate since we will only use DDS texture, which are inverted. Remove if you want to use TGA or BMP loaders.
            temp_uvs.push_back(uv);
        }else if ( strcmp( lineHeader, "vn" ) == 0 ){
            glm::vec3 normal;
            fscanf(file, "%f %f %f\\n", &normal.x, &normal.y, &normal.z );
            temp_normals.push_back(normal);
        }else if ( strcmp( lineHeader, "f" ) == 0 ){
            std::string vertex1, vertex2, vertex3;
            unsigned int vertexIndex[3], uvIndex[3], normalIndex[3];
            int matches = fscanf(file, "%d/%d/%d %d/%d/%d %d/%d/%d\\n", &vertexIndex[0], &uvIndex[0], &normalIndex[0], &vertexIndex[1], &uvIndex[1], &normalIndex[1], &vertexIndex[2], &uvIndex[2], &normalIndex[2] );
            if (matches != 9){
                printf("File can\'t be read by our simple parser :-( Try exporting with other options\\n");
                return false;
            }
            vertexIndices.push_back(vertexIndex[0]);
            vertexIndices.push_back(vertexIndex[1]);
            vertexIndices.push_back(vertexIndex[2]);
            uvIndices    .push_back(uvIndex[0]);
            uvIndices    .push_back(uvIndex[1]);
            uvIndices    .push_back(uvIndex[2]);
            normalIndices.push_back(normalIndex[0]);
            normalIndices.push_back(normalIndex[1]);
            normalIndices.push_back(normalIndex[2]);
        }else{
            // Probably a comment, eat up the rest of the line
            char stupidBuffer[1000];
            fgets(stupidBuffer, 1000, file);
        }

    }

    // For each vertex of each triangle
    for( unsigned int i=0; i<vertexIndices.size(); i++ ){

        // Get the indices of its attributes
        unsigned int vertexIndex = vertexIndices[i];
        unsigned int uvIndex = uvIndices[i];
        unsigned int normalIndex = normalIndices[i];
        
        // Get the attributes thanks to the index
        glm::vec3 vertex = temp_vertices[ vertexIndex-1 ];
        glm::vec2 uv = temp_uvs[ uvIndex-1 ];
        glm::vec3 normal = temp_normals[ normalIndex-1 ];
        
        // Put the attributes in buffers
        out_vertices.push_back(vertex);
        out_uvs     .push_back(uv);
        out_normals .push_back(normal);
    
    }

    return true;
}


#ifdef USE_ASSIMP // don\'t use this #define, it\'s only for me (it AssImp fails to compile on your machine, at least all the other tutorials still work)

// Include AssImp
#include <assimp/Importer.hpp>      // C++ importer interface
#include <assimp/scene.h>           // Output data structure
#include <assimp/postprocess.h>     // Post processing flags

bool loadAssImp(
    const char * path, 
    std::vector<unsigned short> & indices,
    std::vector<glm::vec3> & vertices,
    std::vector<glm::vec2> & uvs,
    std::vector<glm::vec3> & normals
){

    Assimp::Importer importer;

    const aiScene* scene = importer.ReadFile(path, 0/*aiProcess_JoinIdenticalVertices | aiProcess_SortByPType*/);
    if( !scene) {
        fprintf( stderr, importer.GetErrorString());
        getchar();
        return false;
    }
    const aiMesh* mesh = scene->mMeshes[0]; // In this simple example code we always use the 1rst mesh (in OBJ files there is often only one anyway)

    // Fill vertices positions
    vertices.reserve(mesh->mNumVertices);
    for(unsigned int i=0; i<mesh->mNumVertices; i++){
        aiVector3D pos = mesh->mVertices[i];
        vertices.push_back(glm::vec3(pos.x, pos.y, pos.z));
    }

    // Fill vertices texture coordinates
    uvs.reserve(mesh->mNumVertices);
    for(unsigned int i=0; i<mesh->mNumVertices; i++){
        aiVector3D UVW = mesh->mTextureCoords[0][i]; // Assume only 1 set of UV coords; AssImp supports 8 UV sets.
        uvs.push_back(glm::vec2(UVW.x, UVW.y));
    }

    // Fill vertices normals
    normals.reserve(mesh->mNumVertices);
    for(unsigned int i=0; i<mesh->mNumVertices; i++){
        aiVector3D n = mesh->mNormals[i];
        normals.push_back(glm::vec3(n.x, n.y, n.z));
    }


    // Fill face indices
    indices.reserve(3*mesh->mNumFaces);
    for (unsigned int i=0; i<mesh->mNumFaces; i++){
        // Assume the model has only triangles.
        indices.push_back(mesh->mFaces[i].mIndices[0]);
        indices.push_back(mesh->mFaces[i].mIndices[1]);
        indices.push_back(mesh->mFaces[i].mIndices[2]);
    }
    
    // The "scene" pointer will be deleted automatically by "importer"

}

#endif

 

3.common/objloader.hpp

#ifndef OBJLOADER_H
#define OBJLOADER_H

bool loadOBJ(
    const char * path, 
    std::vector<glm::vec3> & out_vertices, 
    std::vector<glm::vec2> & out_uvs, 
    std::vector<glm::vec3> & out_normals
);



bool loadAssImp(
    const char * path, 
    std::vector<unsigned short> & indices,
    std::vector<glm::vec3> & vertices,
    std::vector<glm::vec2> & uvs,
    std::vector<glm::vec3> & normals
);

#endif

 

4. common/controls.cpp

// Include GLFW
#include <glfw3.h>
extern GLFWwindow* window; // The "extern" keyword here is to access the variable "window" declared in tutorialXXX.cpp. This is a hack to keep the tutorials simple. Please avoid this.

// Include GLM
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
using namespace glm;

#include "controls.hpp"

glm::mat4 ViewMatrix;
glm::mat4 ProjectionMatrix;

glm::mat4 getViewMatrix(){
    return ViewMatrix;
}
glm::mat4 getProjectionMatrix(){
    return ProjectionMatrix;
}


// Initial position : on +Z
glm::vec3 position = glm::vec3( 0, 0, 5 ); 
// Initial horizontal angle : toward -Z
float horizontalAngle = 3.14f;
// Initial vertical angle : none
float verticalAngle = 0.0f;
// Initial Field of View
float initialFoV = 45.0f;

float speed = 3.0f; // 3 units / second
float mouseSpeed = 0.005f;



void computeMatricesFromInputs(){

    // glfwGetTime is called only once, the first time this function is called
    static double lastTime = glfwGetTime();

    // Compute time difference between current and last frame
    double currentTime = glfwGetTime();
    float deltaTime = float(currentTime - lastTime);

    // Get mouse position
    double xpos, ypos;
    glfwGetCursorPos(window, &xpos, &ypos);

    // Reset mouse position for next frame
    glfwSetCursorPos(window, 1024/2, 768/2);

    // Compute new orientation
    horizontalAngle += mouseSpeed * float(1024/2 - xpos );
    verticalAngle   += mouseSpeed * float( 768/2 - ypos );

    // Direction : Spherical coordinates to Cartesian coordinates conversion
    glm::vec3 direction(
        cos(verticalAngle) * sin(horizontalAngle), 
        sin(verticalAngle),
        cos(verticalAngle) * cos(horizontalAngle)
    );
    
    // Right vector
    glm::vec3 right = glm::vec3(
        sin(horizontalAngle - 3.14f/2.0f), 
        0,
        cos(horizontalAngle - 3.14f/2.0f)
    );
    
    // Up vector
    glm::vec3 up = glm::cross( right, direction );

    // Move forward
    if (glfwGetKey( window, GLFW_KEY_UP ) == GLFW_PRESS){
        position += direction * deltaTime * speed;
    }
    // Move backward
    if (glfwGetKey( window, GLFW_KEY_DOWN ) == GLFW_PRESS){
        position -= direction * deltaTime * speed;
    }
    // Strafe right
    if (glfwGetKey( window, GLFW_KEY_RIGHT ) == GLFW_PRESS){
        position += right * deltaTime * speed;
    }
    // Strafe left
    if (glfwGetKey( window, GLFW_KEY_LEFT ) == GLFW_PRESS){
        position -= right * deltaTime * speed;
    }

    float FoV = initialFoV;// - 5 * glfwGetMouseWheel(); // Now GLFW 3 requires setting up a callback for this. It\'s a bit too complicated for this beginner\'s tutorial, so it\'s disabled instead.

    // Projection matrix : 45?Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units
    ProjectionMatrix = glm::perspective(FoV, 4.0f / 3.0f, 0.1f, 100.0f);
    // Camera matrix
    ViewMatrix       = glm::lookAt(
                                position,           // Camera is here
                                position+direction, // and looks here : at the same position, plus "direction"
                                up                  // Head is up (set to 0,-1,0 to look upside-down)
                           );

    // For the next frame, the "last time" will be "now"
    lastTime = currentTime;
}

 
5.common/controls.hpp

#ifndef CONTROLS_HPP
#define CONTROLS_HPP

void computeMatricesFromInputs();
glm::mat4 getViewMatrix();
glm::mat4 getProjectionMatrix();

#endif

 

6. common/texture.cpp

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <GL/glew.h>

#include <glfw3.h>


GLuint loadBMP_custom(const char * imagepath){

    printf("Reading image %s\\n", imagepath);

    // Data read from the header of the BMP file
    unsigned char header[54];
    unsigned int dataPos;
    unsigned int imageSize;
    unsigned int width, height;
    // Actual RGB data
    unsigned char * data;

    // Open the file
    FILE * file = fopen(imagepath,"rb");
    if (!file)                                {printf("%s could not be opened. Are you in the right directory ? Don\'t forget to read the FAQ !\\n", imagepath); getchar(); return 0;}

    // Read the header, i.e. the 54 first bytes

    // If less than 54 bytes are read, problem
    if ( fread(header, 1, 54, file)!=54 ){ 
        printf("Not a correct BMP file\\n");
        return 0;
    }
    // A BMP files always begins with "BM"
    if ( header[0]!=\'B\' || header[1]!=\'M\' ){
        printf("Not a correct BMP file\\n");
        return 0;
    }
    // Make sure this is a 24bpp file
    if ( *(int*)&(header[0x1E])!=0  )         {printf("Not a correct BMP file\\n");    return 0;}
    if ( *(int*)&(header[0x1C])!=24 )         {printf("Not a correct BMP file\\n");    return 0;}

    // Read the information about the image
    dataPos    = *(int*)&(header[0x0A]);
    imageSize  = *(int*)&(header[0x22]);
    width      = *(int*)&(header[0x12]);
    height     = *(int*)&(header[0x16]);

    // Some BMP files are misformatted, guess missing information
    if (imageSize==0)    imageSize=width*height*3; // 3 : one byte for each Red, Green and Blue component
    if (dataPos==0)      dataPos=54; // The BMP header is done that way

    // Create a buffer
    data = new unsigned char [imageSize];

    // Read the actual data from the file into the buffer
    fread(data,1,imageSize,file);

    // Everything is in memory now, the file wan be closed
    fclose (file);

    // Create one OpenGL texture
    GLuint textureID;
    glGenTextures(1, &textureID);
    
    // "Bind" the newly created texture : all future texture functions will modify this texture
    glBindTexture(GL_TEXTURE_2D, textureID);

    // Give the image to OpenGL
    glTexImage2D(GL_TEXTURE_2D, 0,GL_RGB, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);

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