适用于Android的OpenGL ES 2.0中的着色器

Question

I want to make some AR stuff. I walked through several steps of some tutorials like

• Displaying Graphics with OpenGL ES
• Learn OpenGL ES

I am Using OpenGL ES 2.0. Especially in the first tutorial they implement some GLSL shader code for the fragment and the vertex shader. And then they compile it.

Do I need to implement such code for every primitive object I want to draw with OpenGL? Or can I reuse shader code for drawing different types of shapes and different instances of the same type of shape?

Furthermore: Can I only reuse shader code or can I also reuse a compiled shader program?

Answer 1

Reusing the same shader for several geometries is a common way of improving performance as they will be treated as a single draw-call. If you set the shader (glUseProgram) it will be available to any number of subsequent calls.

The tutorials are very basic and you should abstract the shader code into a more object oriented approach. For example:

public class Material{
   String mVertexShaderCode;
   String mFragmentShaderCode;
   int mProgram;

   void initialize(){
      // do loadShader and attachShader here
   }

   void draw(){
     GLES20.glUseProgram(mProgram);
     // do more draw stuff
   }
}

Maybe this makes it easier to wrap you head around how you can use and reuse the shader code.

To answer the follow-up question; Yes you can reuse both. The limitation is that you can't use different shader specific attributes if you also reuse the compiled shader. The limitations will become obvious as you start using them.