On Stackoverflow.com
This link is to an Android programming forum, but contains the first framebuffer ES/GLES example code I have seen (to draw triangles on the screen...
The article contains the statement:
Everything is rendered on screen correctly, but the performance are ruined just when I draw the FBO texture. Thank you very much for your help. I worked very hard on this and didn't find a solution.
... so perhaps the code isn't perfect, but it's a place to start. This does confirm what I suspected about library being the home of the GPU e.g. triangle-drawing routines.
Here is what the code looks like – this is C:
// Create a framebuffer and renderbuffer
GLES20.glGenFramebuffers(1, fb, offset);
GLES20.glGenRenderbuffers(1, depthRb, offset);
// Create a texture to hold the frame buffer
GLES20.glGenTextures(1, renderTex, offset);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, renderTex[offset]);
GLES20.glTexImage2D(GLES20.GL_TEXTURE_2D, 0, GLES20.GL_RGBA,
screenWidth, screenHeight, 0,
GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE,
null);
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S,
GLES20.GL_CLAMP_TO_EDGE);
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T,
GLES20.GL_CLAMP_TO_EDGE);
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER,
GLES20.GL_LINEAR);
GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER,
GLES20.GL_LINEAR);
//bind renderbuffer
GLES20.glBindRenderbuffer(GLES20.GL_RENDERBUFFER, depthRb[offset]);
GLES20.glRenderbufferStorage(GLES20.GL_RENDERBUFFER, GLES20.GL_DEPTH_COMPONENT16,
screenWidth, screenHeight);
// bind the framebuffer
GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, fb[offset]);
// specify texture as color attachment
GLES20.glFramebufferTexture2D(GLES20.GL_FRAMEBUFFER, GLES20.GL_COLOR_ATTACHMENT0,
GLES20.GL_TEXTURE_2D, renderTex[offset], 0);
// specify depth_renderbufer as depth attachment
GLES20.glFramebufferRenderbuffer(GLES20.GL_FRAMEBUFFER, GLES20.GL_DEPTH_ATTACHMENT,
GLES20.GL_RENDERBUFFER, depthRb[0]);
// Check FBO status.
int status = GLES20.glCheckFramebufferStatus(GLES20.GL_FRAMEBUFFER);
if ( status == GLES20.GL_FRAMEBUFFER_COMPLETE )
{
Log.d("GLGame framebuffer creation", "Framebuffer complete");
}
// set default framebuffer
GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
On ZipForums.com
Android OpenGL.ES Texture/Image Drawing has more examples of ES/GLES code for Android.
public void onDrawFrame(GL10 gl) {
checkGLError(gl);
if (mContextSupportsFrameBufferObject) {
GL11ExtensionPack gl11ep = (GL11ExtensionPack) gl;
if (DEBUG_RENDER_OFFSCREEN_ONSCREEN) {
drawOffscreenImage(gl, mSurfaceWidth, mSurfaceHeight);
} else {
gl11ep.glBindFramebufferOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, mFramebuffer);
drawOffscreenImage(gl, mFramebufferWidth, mFramebufferHeight);
gl11ep.glBindFramebufferOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, 0);
drawOnscreen(gl, mSurfaceWidth, mSurfaceHeight);
}
} else {
// Current context doesn't support frame buffer objects.
// Indicate this by drawing a red background.
gl.glClearColor(1,0,0,0);
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
}
}
From Google Code
This project is in Java: An OpenGL ES 2.0 example for Android
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