为什么我的三角形在 Raspberry Pi 上的 OpenGL ES 3 中是白色的

Question

我有一个非常简单的 OpenGL ES 程序示例，我试图在 RaspiOS Desktop (a.k.a. Raspbian) 上运行在 Raspberry Pi 4.

我的目标很简单——在屏幕中央画一个红色三角形。但是，三角形显示为白色而不是红色。

我已经搜索并尝试了所有方法，但找不到任何帮助。在这一点上，我感到非常沮丧，因为这本应该是介绍 OpenGL ES 世界的第一个教程，但我已经卡住了，无法继续使用更复杂的示例。

无论如何，这是完整的例子

#include <GL/glew.h>
#include <GL/freeglut.h>
#include <stdio.h>
#include <stdbool.h>

static struct glData {
    GLuint program;
    GLuint vbo;
} glData;

const char vert_shader_source[] = "#version 300 es                         \n"
                                  "precision mediump float;                \n"
                                  "layout (location = 0) in vec3 Position; \n"
                                  "void main()                             \n"
                                  "{                                       \n"
                                  "   gl_Position = vec4(Position, 1.0);   \n"
                                  "}                                       \n";

const char frag_shader_source[] = "#version 300 es                             \n"
                                  "precision mediump float;                    \n"
                                  "out vec4 fragColor;                         \n"
                                  "void main()                                 \n"
                                  "{                                           \n"
                                  "  fragColor = vec4(1.0f, 0.0f, 0.0f, 1.0f); \n"
                                  "}                                           \n";

#define POSITION 0

bool initWindow(int* argc, char** argv)
{
    glutInit(argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_MULTISAMPLE);
    glutCreateWindow("Triangle");
    GLenum glew_status = glewInit();
    if (glew_status != GLEW_OK) {
        fprintf(stderr, "Error: %s\n", glewGetErrorString(glew_status));
        return false;
    }
    return true;
}

static GLuint buildShader(const char* shader_source, GLenum type)
{
    GLuint shader;
    GLint status;

    shader = glCreateShader(type);
    if (shader == 0) {
        return 0;
    }

    glShaderSource(shader, 1, &shader_source, NULL);
    glCompileShader(shader);
    glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
    if (status != GL_TRUE) {
        int length;
        char* log;

        fprintf(stderr, "failed to compile shader\n");
        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &length);
        if (length > 1) {
            log = calloc(length, sizeof(char));
            glGetShaderInfoLog(shader, length, &length, log);
            fprintf(stderr, "%s\n", log);
            free(log);
        }
        return false;
    }

    return true;
}

static GLuint createAndLinkProgram(GLuint v_shader, GLuint f_shader)
{
    GLuint program;
    GLint linked;

    program = glCreateProgram();
    if (program == 0) {
        fprintf(stderr, "failed to create program\n");
        return 0;
    }

    glAttachShader(program, v_shader);
    glAttachShader(program, f_shader);

    glLinkProgram(program);

    glGetProgramiv(program, GL_LINK_STATUS, &linked);

    if (linked != GL_TRUE) {
        int length;
        char* log;

        fprintf(stderr, "failed to link program\n");
        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &length);
        if (length > 1) {
            log = calloc(length, sizeof(char));
            glGetProgramInfoLog(program, length, &length, log);
            fprintf(stderr, "%s\n", log);
            free(log);
        }
        glDeleteProgram(program);
        return 0;
    }

    return program;
}

static bool initProgram()
{
    GLuint v_shader, f_shader;

    v_shader = buildShader(vert_shader_source, GL_VERTEX_SHADER);
    if (v_shader == 0) {
        fprintf(stderr, "failed to build vertex shader\n");
        return false;
    }

    f_shader = buildShader(frag_shader_source, GL_FRAGMENT_SHADER);
    if (f_shader == 0) {
        fprintf(stderr, "failed to build fragment shader\n");
        glDeleteShader(v_shader);
        return false;
    }

    glReleaseShaderCompiler(); // should release resources allocated for the compiler

    glData.program = createAndLinkProgram(v_shader, f_shader);
    if (glData.program == 0) {
        fprintf(stderr, "failed to create and link program\n");
        glDeleteShader(v_shader);
        glDeleteShader(f_shader);
        return false;
    }

    glUseProgram(glData.program);

    // this won't actually delete the shaders until the program is closed but it's a good practice
    glDeleteShader(v_shader);
    glDeleteShader(f_shader);

    return true;
}

bool setupOpenGL()
{
    if (!initProgram()) {
        fprintf(stderr, "failed to initialize program\n");
        return false;
    }

    GLfloat vVertices[] = {
        -0.5f, -0.5f, 0.0f,
        0.0f, 0.5f, 0.0f,
        0.5f, -0.5f, 0.0f,
    };

    glClearColor(0, 0, 0, 1);
    glGenBuffers(1, &glData.vbo);
    glBindBuffer(GL_ARRAY_BUFFER, glData.vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vVertices), vVertices, GL_STATIC_DRAW);

    return true;
}

void reshape(int width, int height)
{
    glViewport(0, 0, width, height);
}

void drawTriangle()
{
    glClear(GL_COLOR_BUFFER_BIT);
    glEnableVertexAttribArray(POSITION);
    glBindBuffer(GL_ARRAY_BUFFER, glData.vbo);
    glVertexAttribPointer(POSITION, 3, GL_FLOAT, GL_FALSE, 0, 0);
    glDrawArrays(GL_TRIANGLES, 0, 3);
    glDisableVertexAttribArray(POSITION);
    glutSwapBuffers();
}

int main(int argc, char** argv)
{
    printf("initialize window\n");
    if (!initWindow(&argc, argv)) {
        fprintf(stderr, "failed to initialize window\n");
        return EXIT_FAILURE;
    }

    printf("setup opengl\n");
    if (!setupOpenGL()) {
        fprintf(stderr, "failed to setup opengl\n");
        return EXIT_FAILURE;
    }

    glutDisplayFunc(drawTriangle);
    glutReshapeFunc(reshape);
    glutMainLoop();

    glDeleteProgram(glData.program);
    return EXIT_SUCCESS;
}

在你运行它之前，你需要：

运行 sudo raspi-config
转到高级选项 > GL 驱动程序
启用 GL（假 KMS）
重启

然后你可以像这样运行编译:

gcc triangle.c -Wall -lm -lglut -lGLEW -lGL -o triangle
./triangle

起初我以为可能是驱动程序中的一些错误或其他问题。但后来我发现 this example 并尝试运行它并且它绘制了一些具有多种颜色的图形并且它很好。

如果有任何帮助，我将不胜感激。几天来我一直在尝试调试它。

Answer 1

Nvm，原来我是个白痴

这整个时间都是 buildShader() 函数中的一个简单拼写错误。这是该函数的固定版本：

static GLuint buildShader(const char* shader_source, GLenum type)
{
    GLuint shader;
    GLint status;

    shader = glCreateShader(type);
    if (shader == 0) {
        return 0;
    }

    glShaderSource(shader, 1, &shader_source, NULL);
    glCompileShader(shader);
    glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
    if (status != GL_TRUE) {
        int length;
        char* log;

        fprintf(stderr, "failed to compile shader\n");
        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &length);
        if (length > 1) {
            log = calloc(length, sizeof(char));
            glGetShaderInfoLog(shader, length, &length, log);
            fprintf(stderr, "%s\n", log);
            free(log);
        }
        return 0;
    }

    return shader;
}

问题是我不小心返回了 true/false 而不是着色器。我完全不知道程序是如何做到运行没有错误并显示一个白色三角形的，但事实就是如此。

为什么我的三角形在 Raspberry Pi 上的 OpenGL ES 3 中是白色的

Why is my triangle white in OpenGL ES 3 on Raspberry Pi

c

opengl-es

raspberry-pi

opengl-es-3.0

opengl-es-3.1