不同的片段着色器颜色

Question

我想用着色器绘制不同颜色的不同图形。

我尝试使用统一变量并使用网格的顶点属性来分隔顶点缓冲区对象，但是当我运行程序仅使用第二种颜色并且根本不显示第一个图形时。我不确定这是我绑定着色器的方式还是我使用统一变量的方式的问题。提前致谢。

代码如下：

#include <GL/glew.h>
#include <GL/glut.h>
#include <stdio.h>

const char* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
"   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}[=10=]";

const char* fragmentShaderSource = "#version 330 core\n"
"in vec4 color;\n"
"out vec4 FragColor;\n"
"uniform vec3 figColor;\n"
"void main()\n"
"{\n"
"   FragColor = vec4(figColor, 0.0f);\n"
"}\n[=10=]";

// Set of vertices that draw the different figures:
float vertices1[] = { 
    -0.8f, 0.6f, 0.0f, 
    -0.8f, 0.4f, 0.0f,
    -0.83f, 0.44f, 0.0f,
    -0.87f, 0.51f, 0.0f,
    -0.9f, 0.57f, 0.0f,
    -0.93f, 0.63f, 0.0f,
    -0.95f, 0.69f, 0.0f,
    -0.97f, 0.75f, 0.0f,
    -0.98f, 0.8f, 0.0f,
    -0.91f, 0.8f, 0.0f,
    -0.85f, 0.79f, 0.0f,
    -0.8f, 0.77f, 0.0f,
};

float vertices2[] = {
    -0.8f, -0.15f, 0.0f, 
    -1.0f, 0.0f, 0.0f,
    -0.95f, 0.0f, 0.0f,
    -0.86f, -0.01f, 0.0f,
    -0.81f, -0.02f, 0.0f,
    -0.75f, -0.03f, 0.0f,
};

GLuint vertexShader;
GLuint fragmentShader;
GLuint shaderProgram;

void display(void) {
    // Background color.
    glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    glUseProgram(shaderProgram);
    GLint uniform = glGetUniformLocation(shaderProgram, "figColor");
    glUniform3f(uniform, 1.0f, 0.0f, 0.0f);
    glDrawArrays(GL_TRIANGLE_FAN, 0, 12);
    glUniform3f(uniform, 0.0f, 0.749f, 1.0f);
    glDrawArrays(GL_TRIANGLE_FAN, 0, 6);
    glUseProgram(0);

    glFlush();
}

// Main.
int main(int argc, char** argv) {
    glutInit(&argc, argv);
    // Color mode.
    glutInitDisplayMode(GLUT_RGBA);
    // Window size.
    glutInitWindowSize(500, 500);
    // Title.
    glutCreateWindow("Tarea 3: Figura con curvas");
    GLenum err = glewInit();
    if (err != GLEW_OK) {
        printf("glewInit failed: %s", glewGetErrorString(err));
        exit(1);
    }

    // Compile vertex shader.
    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    // Check for vertex shader compilation errors.   
    int success;
    char infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        printf("ERROR::SHADER::VERTEX::COMPILATION_FAILED\n");
    }

    // Compile fragment shader.
    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);

    // Check for fragment shader compile errors.  
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        printf("ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n");
    }

    // Link and delete shaders.
    shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

    //Separating the Vertex Buffer Objects.
    GLuint VBOs[2];
    glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices1), vertices1, GL_STATIC_DRAW);

    glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);

    // Specify a VertexArrayObject for each mesh.
    GLuint VAOs[2];
    glGenVertexArrays(2, VAOs);

    glBindVertexArray(VAOs[0]);
    glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glBindVertexArray(VAOs[1]);
    glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    // Bind the VAO before the draw call.
    glBindVertexArray(VAOs[0]);
    glDrawArrays(GL_TRIANGLE_FAN, 0, 12);

    glBindVertexArray(VAOs[1]);
    glDrawArrays(GL_TRIANGLE_FAN, 0, 24);

    // Displaying the figures.
    glutDisplayFunc(display);
    glutMainLoop();
}

Answer 1

您未能生成顶点缓冲区对象名称：

//Separating the Vertex Buffer Objects.
GLuint VBOs[2];
glGenBuffers(2, VBOs); <----

在主循环中绘制网格之前必须绑定顶点数组：

GLuint VAOs[2];

void display(void) {
    // Background color.
    glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    glUseProgram(shaderProgram);
    GLint uniform = glGetUniformLocation(shaderProgram, "figColor");
    
    glUniform3f(uniform, 1.0f, 0.0f, 0.0f);
    glBindVertexArray(VAOs[0]);                     // <---
    glDrawArrays(GL_TRIANGLE_FAN, 0, 12);
    
    glUniform3f(uniform, 0.0f, 0.749f, 1.0f);
    glBindVertexArray(VAOs[1]);                     // <----
    glDrawArrays(GL_TRIANGLE_FAN, 0, 6);
    glUseProgram(0);

    glFlush();
}

int main(int argc, char** argv) {
    // [...]

    // Specify a VertexArrayObject for each mesh.
    // GLuint VAOs[2]; <---- DELETE
    glGenVertexArrays(2, VAOs);

    // [...]

    // DELETE
    /*
    // Bind the VAO before the draw call.
    glBindVertexArray(VAOs[0]);
    glDrawArrays(GL_TRIANGLE_FAN, 0, 12);

    glBindVertexArray(VAOs[1]);
    glDrawArrays(GL_TRIANGLE_FAN, 0, 24);
    */

    // [...]

不同的片段着色器颜色

Different fragment shader colors

c++

opengl

glut

glew