How to use multiple textures in OpenGL ES 2.0?

Question

I am working in OpenGL ES 2.0.

I load two png images as my textures with the libSOIL. I need to use one of them as the texture for the background and another one as the texture of a rotating cube.

In OpenGL ES 2.0, the adding texture operation is in the shader. I don't know how to add the different textures to the different places in a shader. How do I do that?

Answer 1

Simplest way is multiple draw calls.

In OpenGL ES 2.0, the adding texture operation is in the shader

Not really. How does shaders know where to take texture pixels? You must bind texture outside shader too.

Basic algorithm for drawing multiple objects is:

for(each object obj)
{
    SetPipelineState(obj);
    Draw(obj);
}

In your case:

void RenderFrame()
{
    ClearBackBuffer();
    ClearDepthBuffer();

    // Draw cube
    glUseProgram(programForCube);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, textureOfCube);  // Texture for cube
    glBindBuffer(...) // Vertex buffer for cube
    // other states go here
    Draw(...);

    // Draw background
    glUseProgram(programForBackground);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, textureOfBackground); // Texture for background
    glBindBuffer(...) // Vertex buffer for background
    // other states go here
    Draw(...);
}

Don't forget to set up depth state and depth buffer.

There are advanced techniques to reduce draw calls number.

Even better and more general solution will be to google up complete OpenGL tutorial course. There are plenty on the web.