How to use VAOs in OpenGL ES 2.0
I've read that using VAOs is recommended but I don't know how. I am using the tegra android development pack (which uses OpenGL ES 2.0) and I can't find the methodes glGenVertexArrays and glBindVertexArray. Are VAOs supported in ES 2.0 (without extensions)?
Also I don't understand what the benefit of a VAO is. Currently I compile the shaders and use glBindAttribLocation. After that I define the vertex positions and colors for a triangle and use glVertexAttribPointer. Then I just draw the triangle again and again.
This is the program (without error checks):
static void createProgram() {
// vertex shader
const char* vertexShaderCode = getVertexShaderCode();
GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderCode, NULL);
glCompileShader(vertexShader);
// fragment shader
const char* fragmentShaderCode = getFragmentShaderCode();
GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderCode, NULL);
glCompileShader(fragmentShader);
// create program
program = glCreateProgram();
glAttachShader(program, vertexShader);
glAttachShader(program, fragmentShader);
// Dem Programm sagen, unter welchem Index die Daten der Shader Attribute liegen
glBindAttribLocation(program, 1, "in_pos");
glBindAttribLocation(program, 2, "in_color");
glLinkProgram(program);
}
And this is the triangle:
static void loadGeometry() {
GLuint buffers[2];
glGenBuffers(2, buffers);
GLuint vboPosition = buffers[0];
GLuint vboColor = buffers[1];
const int VERTEX_POSITION_BUFFER_SIZE = 12;
const int VERTEX_POSITION_BUFFER_BYTESIZE = sizeof(GLfloat)* VERTEX_POSITION_BUFFER_SIZE;
GLfloat vertexPositionBuffer[VERTEX_POSITION_BUFFER_SIZE] = {
0.0f, 0.5f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.0f, 1.0f,
0.5f, -0.5f, 0.0f, 1.0f };
glBindBuffer(GL_ARRAY_BUFFER, vboPosition);
glBufferData(GL_ARRAY_BUFFER, VERTEX_POSITION_BUFFER_BYTESIZE, vertexPositionBuffer, GL_STATIC_DRAW);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, 0);
// Repeat for color...
}
And in the draw call I just do
glUseProgram(program);
glDrawArrays(GL_TRIANGLES, 0, 3);