ubuntu - How to develop OpenGL ES (GLES) 2.0 applications on Linux?

Question

I would like to develop OpenGL ES 2.0 apps on my Ubuntu machine. I could not find any libraries/emulators that support GLES 2.0 yet. Any suggestions?

Answer 1

GLFW, Mesa, Ubuntu 16.04 AMD64

This was not easy to setup on Ubuntu 14.04, but now it just works.

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

Output:

glfw_triangle.c

#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
"
    "attribute vec3 position;
"
    "void main() {
"
    "   gl_Position = vec4(position, 1.0);
"
    "}
";
static const GLchar* fragment_shader_source =
    "#version 100
"
    "void main() {
"
    "   gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
"
    "}
";
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
%s
", 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
%s
", 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
%s
", 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
", glGetString(GL_VERSION) );
    printf("GL_RENDERER : %s
", 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;
}

The key line lines of code are:

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

GLFW_INCLUDE_ES2 is documented at: http://www.glfw.org/docs/latest/build_guide.html#build_macros and a quick look at the source shows that it forwards to GLES:

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

This source seems to be written in the common subset of GLES and OpenGL (like much of GLES), and also compiles with -lGL if we remove the #define GLFW_INCLUDE_ES2.

If we add things which are not in GLES like immediate rendering glBegin, link fails as expected.

See also: https://askubuntu.com/questions/244133/how-do-i-get-egl-and-opengles-libraries-for-ubuntu-running-on-virtualbox

Credits: genpfult made the code much more correct.

ARM Mali OpenGL ES SDK

• download from: http://malideveloper.arm.com/resources/sdks/opengl-es-sdk-for-linux/
• open the documentation HTML on a browser
• follow the "Quick Start Guide", it's simple

Contains several interesting open source examples + windowing system boilerplate (X11 + EGL).

The build system supports easy cross compilation for ARM / Mali SoCs, but I haven't tested that yet.

The key component included seems to be the "OpenGL ES Emulator" http://malideveloper.arm.com/resources/tools/opengl-es-emulator/ which "maps OpenGL ES 3.2 API calls to the OpenGL API". But that does not ship with source, only precompiled.

Uses a custom enterprisey EULA that appears to be permissive, but yeah, ask your lawyer.

Tested on SDK v2.4.4.