在x86 Linux上用C++编写的任何GLES示例？

Question

我在X86的x86 Linux上寻找C++(或C)的GLES2样本的良好来源.我可以找到的样本都是针对iOS的Objective C,或针对Android的Java,或针对WebGL的JavaScript.Kronos网站有一个"教程"部分,其中包含两行"我们的教程索引将在此处".鉴于GLES2已有5年历史,我对那里的内容突然激增并不抱太大希望.

我已经非常了解OpenGL了.我真的想要一些方便的复制粘贴上下文设置代码源.我在哪里可以找到类似的东西？

Answer 1

梅萨演示!

• http://cgit.freedesktop.org/mesa/demos
• http://cgit.freedesktop.org/mesa/demos/tree/src/egl/opengles2
• http://cgit.freedesktop.org/mesa/demos/tree/src/egl/opengles2/es2tri.c

Answer 2

GLFW,Mesa,Ubuntu 16.04 AMD64

我不确定GLUT是否支持GLES,但GLFW确实支持GLES ,大大简化了窗口管理.

sudo apt-get install libglfw3-dev libgles2-mesa-dev
gcc glfw_triangle.c -lGLESv2 -lglfw

输出:

资源:

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

#define GLFW_INCLUDE_ES2
#include <GLFW/glfw3.h>

static const GLuint WIDTH = 800;
static const GLuint HEIGHT = 600;
static const GLchar* vertex_shader_source =
    "#version 100\n"
    "attribute vec3 position;\n"
    "void main() {\n"
    "   gl_Position = vec4(position, 1.0);\n"
    "}\n";
static const GLchar* fragment_shader_source =
    "#version 100\n"
    "void main() {\n"
    "   gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n"
    "}\n";
static const GLfloat vertices[] = {
        0.0f,  0.5f, 0.0f,
        0.5f, -0.5f, 0.0f,
    -0.5f, -0.5f, 0.0f,
};

GLint common_get_shader_program(const char *vertex_shader_source, const char *fragment_shader_source) {
    enum Consts {INFOLOG_LEN = 512};
    GLchar infoLog[INFOLOG_LEN];
    GLint fragment_shader;
    GLint shader_program;
    GLint success;
    GLint vertex_shader;

    /* Vertex shader */
    vertex_shader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex_shader, 1, &vertex_shader_source, NULL);
    glCompileShader(vertex_shader);
    glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(vertex_shader, INFOLOG_LEN, NULL, infoLog);
        printf("ERROR::SHADER::VERTEX::COMPILATION_FAILED\n%s\n", infoLog);
    }

    /* Fragment shader */
    fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment_shader, 1, &fragment_shader_source, NULL);
    glCompileShader(fragment_shader);
    glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(fragment_shader, INFOLOG_LEN, NULL, infoLog);
        printf("ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n%s\n", infoLog);
    }

    /* Link shaders */
    shader_program = glCreateProgram();
    glAttachShader(shader_program, vertex_shader);
    glAttachShader(shader_program, fragment_shader);
    glLinkProgram(shader_program);
    glGetProgramiv(shader_program, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shader_program, INFOLOG_LEN, NULL, infoLog);
        printf("ERROR::SHADER::PROGRAM::LINKING_FAILED\n%s\n", infoLog);
    }

    glDeleteShader(vertex_shader);
    glDeleteShader(fragment_shader);
    return shader_program;
}

int main(void) {
    GLuint shader_program, vbo;
    GLint pos;
    GLFWwindow* window;

    glfwInit();
    glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_ES_API);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    window = glfwCreateWindow(WIDTH, HEIGHT, __FILE__, NULL, NULL);
    glfwMakeContextCurrent(window);

    printf("GL_VERSION  : %s\n", glGetString(GL_VERSION) );
    printf("GL_RENDERER : %s\n", glGetString(GL_RENDERER) );

    shader_program = common_get_shader_program(vertex_shader_source, fragment_shader_source);
    pos = glGetAttribLocation(shader_program, "position");

    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    glViewport(0, 0, WIDTH, HEIGHT);

    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glVertexAttribPointer(pos, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
    glEnableVertexAttribArray(pos);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    while (!glfwWindowShouldClose(window)) {
        glfwPollEvents();
        glClear(GL_COLOR_BUFFER_BIT);
        glUseProgram(shader_program);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glfwSwapBuffers(window);
    }
    glDeleteBuffers(1, &vbo);
    glfwTerminate();
    return EXIT_SUCCESS;
}

关键的代码行是:

#define GLFW_INCLUDE_ES2
#include <GLFW/glfw3.h>

GLFW_INCLUDE_ES2记录在以下网址:http://www.glfw.org/docs/latest/build_guide.html#build_macros,快速查看来源显示它转发给GLES:

 #elif defined(GLFW_INCLUDE_ES2)
  #include <GLES2/gl2.h>
  #if defined(GLFW_INCLUDE_GLEXT)
   #include <GLES2/gl2ext.h>
  #endif

这个源似乎是GLES和OpenGL的常见子集(就像很多GLES一样),并且-lGL如果我们删除了它,也可以编译#define GLFW_INCLUDE_ES2.

如果我们添加不像GLES那样立即呈现的内容glBegin,则链接会按预期失败.

另请参见:如何在Linux上开发OpenGL ES(GLES)2.0应用程序？

致谢:genpfult使代码更加正确.

ARM Mali OpenGL ES SDK

• 下载地址:http://malideveloper.arm.com/resources/sdks/opengl-es-sdk-for-linux/
• 在浏览器上打开文档HTML
• 按照"快速入门指南",它很简单

包含几个有趣的开源示例+窗口系统样板(X11 + EGL).

构建系统支持ARM/Mali SoC的简单交叉编译,但我还没有测试过.

包含的关键组件似乎是"OpenGL ES Emulator" http://malideveloper.arm.com/resources/tools/opengl-es-emulator/,它"将OpenGL ES 3.2 API调用映射到OpenGL API".但是这不包含源代码,只是预编译.

使用看似宽容的定制企业EULA,但是,请问你的律师.

在SDK v2.4.4上测试.