c++ - 使用不同纹理对多个对象进行纹理化

Question

有人可以为我解释一下如何在 OpenGL 中渲染具有不同纹理的多个对象吗？

我认为我接近最终结果，但此刻我被困在这里，我不知道下一步需要做什么。真的需要一些帮助!

目前这就是我所拥有的:

1. drawSphere():根据 longs 和 lats 的数量绘制 UV 球体

   int numberOfVerices = 0;

   for(int i = 0; i <= lats; i++) {
       double lat0 = M_PI * (-0.5 + (double) (i - 1) / lats);
       double z0  = sin(lat0);
       double zr0 =  cos(lat0);
   
       double lat1 = M_PI * (-0.5 + (double) i / lats);
       double z1 = sin(lat1);
       double zr1 = cos(lat1);
   
       for(int j = 0; j <= longs; j++) {
           double lng = 2 * M_PI * (double) (j - 1) / longs;
           double x = cos(lng);
           double y = sin(lng);
   
           glNormal3f(x * zr0, y * zr0, z0);
   
           vertices.push_back(x * zr0);
           vertices.push_back(y * zr0);
           vertices.push_back(z0);
           indices.push_back(numberOfVerices);
           numberOfVerices++;
   
           vertices.push_back(x * zr1);
           vertices.push_back(y * zr1);
           vertices.push_back(z1);
           indices.push_back(numberOfVerices);
           numberOfVerices++;
      }
      indices.push_back(GL_PRIMITIVE_RESTART_FIXED_INDEX);
   }
   

2. SetupGeometry():该方法用于绑定(bind)顶点和纹理坐标。

绘制球体(300, 300);

glGenBuffers(1, &vboVertex);
glBindBuffer(GL_ARRAY_BUFFER, vboVertex);
glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(GLfloat), &vertices[0], GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glEnableVertexAttribArray(0);

glGenBuffers(1, &vboTexture);
glBindBuffer(GL_ARRAY_BUFFER, vboTexture);
glBufferData(GL_ARRAY_BUFFER, texture.size() * sizeof(GLfloat), &texture[0], GL_STATIC_DRAW);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(1);

glGenBuffers(1, &vboIndex);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboIndex);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size() * sizeof(GLuint), &indices[0], GL_STATIC_DRAW);

numsToDraw = indices.size();
nums = indices.size();

1. SetupShader():创建着色器并编译着色器

字 rune 本[1000]; 整数长度；

vertexSource = filetobuf("space/sphere.vert");
fragmentSource = filetobuf("space/sphere.frag");

vertexShader = glCreateShader(GL_VERTEX_SHADER);
fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);

glShaderSource(vertexShader, 1, (const GLchar**) &vertexSource, 0);
glShaderSource(fragmentShader, 1, (const GLchar**) &fragmentSource, 0);

fprintf(stderr, "Compiling vertex shader....\n");
glCompileShader(vertexShader);
fprintf(stderr, "Compiling fragment shader....\n");
glCompileShader(fragmentShader);
fprintf(stderr, "Done....\n");

shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);

glBindAttribLocation(shaderProgram, 0, "in_Position");
glBindAttribLocation(shaderProgram, 1, "Texture_Coord");

printf("Linking program ... \n");
glLinkProgram(shaderProgram);

glGetProgramInfoLog(shaderProgram, 1000, &length, text);
if(length > 0){
    fprintf(stderr, "Validate Shader Program\n%s\n", text );
}

glUseProgram(shaderProgram);

1. SetupTexture(char * filename):加载图像，生成2个纹理数组，一个到GL_TEXTURE0，另一个到GL_TEXTURE1

GLuint 纹理[2]； glGenTextures(2, 纹理);

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture[0]);
data = stbi_load(fileName, &w, &h, &n, 0);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
glUniform1i(glGetUniformLocation(shaderProgram, "texture_Sun"), 0);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
stbi_image_free(data);

glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, texture[1]);
data = stbi_load(fileName1, &w, &h, &n, 0);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
glUniform1i(glGetUniformLocation(shaderProgram, "texture_Earth"), 1);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
stbi_image_free(data);

1. Render(int i):渲染2个物体，即球体。

glClearColor(0.0, 0.0, 0.0, 1.0);/* 将我们的背景设为黑色 */ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glEnable(GL_PRIMITIVE_RESTART);
glPrimitiveRestartIndex(GL_PRIMITIVE_RESTART_FIXED_INDEX);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboIndex);

glPushMatrix();
glLoadIdentity();
glm::mat4 Projection = glm::perspective(50.0f, 5.0f / 3.0f, 1.0f, 100.0f);
    glm::mat4 View = glm::lookAt(
        glm::vec3(0, 5, 2),
        glm::vec3(0, 0, 0),
        glm::vec3(0, 1, 0)
    );

    /* Animations */
    GLfloat angle = (GLfloat) (i);
    View = glm::translate(View, glm::vec3(2.0f, 0.0f, 0.0f));
    View = glm::rotate(View, angle * 0.5f, glm::vec3(0.0f, 0.0f, 1.0f));
    /* ******* */

    glm::mat4 Model = glm::mat4(1.0f);
    glm::mat4 MVP = Projection * View * Model;

    glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "mvpMatrix"), 1, GL_FALSE, glm::value_ptr(MVP));
glDrawElements(GL_QUAD_STRIP, numsToDraw, GL_UNSIGNED_INT, NULL);
glPopMatrix();

glPushMatrix();
glLoadIdentity();
glm::mat4 Projection1 = glm::perspective(50.0f, 5.0f / 3.0f, 1.0f, 100.0f);
    glm::mat4 View1 = glm::lookAt(
        glm::vec3(0, 5, 2),
        glm::vec3(0, 0, 0),
        glm::vec3(0, 1, 0)
    );

    /* Animations */
    GLfloat angle1 = (GLfloat) (i);
    View1 = glm::translate(View1, glm::vec3(-2.0f, 0.0f, 0.0f));
    View1 = glm::rotate(View1, angle1 * -0.5f, glm::vec3(0.0f, 0.0f, 1.0f));
    /* ******* */

    glm::mat4 Model1 = glm::mat4(1.0f);
    MVP = Projection1 * View1 * Model1;

    glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "mvpMatrix"), 1, GL_FALSE, glm::value_ptr(MVP));
glDrawElements(GL_QUAD_STRIP, nums, GL_UNSIGNED_INT, NULL);
glPopMatrix();

顶点着色器:

#version 330 core
precision highp float;
attribute vec3 in_Position;
attribute vec3 in_Position1;
varying vec4 Texture_Coord;

uniform mat4 mvpMatrix;

void main(void){
    gl_Position = mvpMatrix * vec4(in_Position, 1.0);
    Texture_Coord = vec4(in_Position, 1.0);
}

片段着色器:

#version 330 core
precision highp float;
varying vec4 Texture_Coord;

uniform sampler2D texture_Sun;
uniform sampler2D texture_Earth;

out vec4 FragColor;

void main(void){
    vec2 longLat = vec2((atan(Texture_Coord.y, Texture_Coord.x)/3.1415926 + 1) * 0.5, (asin(Texture_Coord.z) / 3.1415926 + 0.5));

    FragColor = texture2D(texture_Sun, longLat);
    FragColor = texture2D(texture_Earth, longLat);
}

main中的主要代码:

SetupGeomtry();
    SetupShader();
    SetupTexture("images/Earth.jpg", "images/sun.jpg");
    /*
     *  Main loop
     */
    int i = 0;
    while(!glfwWindowShouldClose(window)){
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        Render(i+=1);
        glfwSwapBuffers(window);
        glfwPollEvents();
        Sleep(10);
    }

Answer 1

通常你会加载你的纹理(即将它们缓冲到 GPU):

GLuint texture[2];
glGenTextures(2, texture);

glBindTexture(GL_TEXTURE_2D, texture[0]);
data = stbi_load(fileName, &w, &h, &n, 0);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
stbi_image_free(data);

glBindTexture(GL_TEXTURE_2D, texture[1]);
data = stbi_load(fileName1, &w, &h, &n, 0);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
stbi_image_free(data);

然后在绘制每个对象之前绑定(bind)所述对象的相关纹理:

// already selected the shader programme for both Sun and Earth
GLint textureLocation = glGetUniformLocation(shaderProgram, "texture_CelestialBody");
// optionally remember more locations for multi texture

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture[0]);
glUniform1i(textureLocation, 0);
// optionally bind more textures for multi texture shader...
// draw Sun now

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture[1]);
glUniform1i(textureLocation, 0);
// optionally bind more textures for multi texture shader...
// draw Earth now

然后 texture_CelestialBody 识别太阳和地球的纹理 - 即片段着色器不会区分两者。