+ * This sample renders a scene into an offscreen frame buffer, and then + * uses the resulting image as a texture to render an onscreen scene. + */ +public class FrameBufferObjectActivity extends Activity { + private GLSurfaceView mGLSurfaceView; + + private class Renderer implements GLSurfaceView.Renderer { + private boolean mContextSupportsFrameBufferObject; + private int mTargetTexture; + private int mFramebuffer; + private int mFramebufferWidth = 256; + private int mFramebufferHeight = 256; + private int mSurfaceWidth; + private int mSurfaceHeight; + + private Triangle mTriangle; + private Cube mCube; + private float mAngle; + private boolean mDebugOffscreenRenderer = false; + + public void onDrawFrame(GL10 gl) { + checkGLError(gl); + if (mContextSupportsFrameBufferObject) { + GL11ExtensionPack gl11ep = (GL11ExtensionPack) gl; + if (mDebugOffscreenRenderer) { + 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); + } + } + + public void onSurfaceChanged(GL10 gl, int width, int height) { + checkGLError(gl); + mSurfaceWidth = width; + mSurfaceHeight = height; + gl.glViewport(0, 0, width, height); + } + + public void onSurfaceCreated(GL10 gl, EGLConfig config) { + mContextSupportsFrameBufferObject = checkIfContextSupportsFrameBufferObject(gl); + if (mContextSupportsFrameBufferObject) { + mTargetTexture = createTargetTexture(gl, mFramebufferWidth, mFramebufferHeight); + mFramebuffer = createFrameBuffer(gl, mFramebufferWidth, mFramebufferHeight, mTargetTexture); + + mCube = new Cube(); + mTriangle = new Triangle(); + } + } + + private void drawOnscreen(GL10 gl, int width, int height) { + gl.glViewport(0, 0, width, height); + float ratio = (float) width / height; + gl.glMatrixMode(GL10.GL_PROJECTION); + gl.glLoadIdentity(); + gl.glFrustumf(-ratio, ratio, -1, 1, 3, 7); + + gl.glClearColor(0,0,1,0); + gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); + gl.glBindTexture(GL10.GL_TEXTURE_2D, mTargetTexture); + + gl.glTexEnvf(GL10.GL_TEXTURE_ENV, GL10.GL_TEXTURE_ENV_MODE, + GL10.GL_REPLACE); + + gl.glMatrixMode(GL10.GL_MODELVIEW); + gl.glLoadIdentity(); + + GLU.gluLookAt(gl, 0, 0, -5, 0f, 0f, 0f, 0f, 1.0f, 0.0f); + + gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); + gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); + + gl.glActiveTexture(GL10.GL_TEXTURE0); + + long time = SystemClock.uptimeMillis() % 4000L; + float angle = 0.090f * ((int) time); + + gl.glRotatef(angle, 0, 0, 1.0f); + + mTriangle.draw(gl); + + // Restore default state so the other renderer is not affected. + + gl.glBindTexture(GL10.GL_TEXTURE_2D, 0); + gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); + gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); + } + + private void drawOffscreenImage(GL10 gl, int width, int height) { + gl.glViewport(0, 0, width, height); + float ratio = (float) width / height; + gl.glMatrixMode(GL10.GL_PROJECTION); + gl.glLoadIdentity(); + gl.glFrustumf(-ratio, ratio, -1, 1, 1, 10); + + gl.glEnable(GL10.GL_CULL_FACE); + gl.glEnable(GL10.GL_DEPTH_TEST); + + gl.glClearColor(0,0.5f,1,0); + gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); + gl.glMatrixMode(GL10.GL_MODELVIEW); + gl.glLoadIdentity(); + gl.glTranslatef(0, 0, -3.0f); + gl.glRotatef(mAngle, 0, 1, 0); + gl.glRotatef(mAngle*0.25f, 1, 0, 0); + + gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); + gl.glEnableClientState(GL10.GL_COLOR_ARRAY); + + mCube.draw(gl); + + gl.glRotatef(mAngle*2.0f, 0, 1, 1); + gl.glTranslatef(0.5f, 0.5f, 0.5f); + + mCube.draw(gl); + + mAngle += 1.2f; + + // Restore default state so the other renderer is not affected. + + gl.glDisable(GL10.GL_CULL_FACE); + gl.glDisable(GL10.GL_DEPTH_TEST); + gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); + gl.glDisableClientState(GL10.GL_COLOR_ARRAY); + } + + private int createTargetTexture(GL10 gl, int width, int height) { + int texture; + int[] textures = new int[1]; + gl.glGenTextures(1, textures, 0); + texture = textures[0]; + gl.glBindTexture(GL10.GL_TEXTURE_2D, texture); + gl.glTexImage2D(GL10.GL_TEXTURE_2D, 0, GL10.GL_RGBA, width, height, 0, + GL10.GL_RGBA, GL10.GL_UNSIGNED_BYTE, null); + gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, + GL10.GL_NEAREST); + gl.glTexParameterf(GL10.GL_TEXTURE_2D, + GL10.GL_TEXTURE_MAG_FILTER, + GL10.GL_LINEAR); + gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, + GL10.GL_REPEAT); + gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, + GL10.GL_REPEAT); +; return texture; + } + + private int createFrameBuffer(GL10 gl, int width, int height, int targetTextureId) { + GL11ExtensionPack gl11ep = (GL11ExtensionPack) gl; + int framebuffer; + int[] framebuffers = new int[1]; + gl11ep.glGenFramebuffersOES(1, framebuffers, 0); + framebuffer = framebuffers[0]; + gl11ep.glBindFramebufferOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, framebuffer); + + int depthbuffer; + int[] renderbuffers = new int[1]; + gl11ep.glGenRenderbuffersOES(1, renderbuffers, 0); + depthbuffer = renderbuffers[0]; + + gl11ep.glBindRenderbufferOES(GL11ExtensionPack.GL_RENDERBUFFER_OES, depthbuffer); + gl11ep.glRenderbufferStorageOES(GL11ExtensionPack.GL_RENDERBUFFER_OES, + GL11ExtensionPack.GL_DEPTH_COMPONENT16, width, height); + gl11ep.glFramebufferRenderbufferOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, + GL11ExtensionPack.GL_DEPTH_ATTACHMENT_OES, + GL11ExtensionPack.GL_RENDERBUFFER_OES, depthbuffer); + + gl11ep.glFramebufferTexture2DOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, + GL11ExtensionPack.GL_COLOR_ATTACHMENT0_OES, GL10.GL_TEXTURE_2D, + targetTextureId, 0); + int status = gl11ep.glCheckFramebufferStatusOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES); + if (status != GL11ExtensionPack.GL_FRAMEBUFFER_COMPLETE_OES) { + throw new RuntimeException("Framebuffer is not complete: " + + Integer.toHexString(status)); + } + gl11ep.glBindFramebufferOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, 0); + return framebuffer; + } + + private boolean checkIfContextSupportsFrameBufferObject(GL10 gl) { + return checkIfContextSupportsExtension(gl, "GL_OES_framebuffer_object"); + } + + /** + * This is not the fastest way to check for an extension, but fine if + * we are only checking for a few extensions each time a context is created. + * @param gl + * @param extension + * @return true if the extension is present in the current context. + */ + private boolean checkIfContextSupportsExtension(GL10 gl, String extension) { + String extensions = " " + gl.glGetString(GL10.GL_EXTENSIONS) + " "; + // The extensions string is padded with spaces between extensions, but not + // necessarily at the beginning or end. For simplicity, add spaces at the + // beginning and end of the extensions string to make it easy to find an + // extension. + return extensions.indexOf(" " + extension + " ") >= 0; + } + } + + static void checkGLError(GL gl) { + int error = ((GL10) gl).glGetError(); + if (error != GL10.GL_NO_ERROR) { + throw new RuntimeException("GLError 0x" + Integer.toHexString(error)); + } + } + + @Override + protected void onCreate(Bundle savedInstanceState) { + super.onCreate(savedInstanceState); + + // Create our surface view and set it as the content of our + // Activity + mGLSurfaceView = new GLSurfaceView(this); + mGLSurfaceView.setRenderer(new Renderer()); + setContentView(mGLSurfaceView); + } + + @Override + protected void onResume() { + // Ideally a game should implement onResume() and onPause() + // to take appropriate action when the activity looses focus + super.onResume(); + mGLSurfaceView.onResume(); + } + + @Override + protected void onPause() { + // Ideally a game should implement onResume() and onPause() + // to take appropriate action when the activity looses focus + super.onPause(); + mGLSurfaceView.onPause(); + } +}