samples/ApiDemos/src/com/example/android/apis/graphics/FrameBufferObjectActivity.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.graphics;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL;
import javax.microedition.khronos.opengles.GL10;
import javax.microedition.khronos.opengles.GL11ExtensionPack;

import android.app.Activity;
import android.opengl.GLSurfaceView;
import android.opengl.GLU;
import android.os.Bundle;
import android.os.SystemClock;

/**
 * Demonstrate the Frame Buffer Object OpenGL ES extension.
 * <p>
 * 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;
        /**
         * Setting this to true will change the behavior  of this sample. It
         * will suppress the normally onscreen rendering, and it will cause the
         * rendering that would normally be done to the offscreen FBO
         * be rendered onscreen instead. This can be helpful in debugging the
         * rendering algorithm.
         */
        private static final boolean DEBUG_RENDER_OFFSCREEN_ONSCREEN = false;

        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);
            }
        }

        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 and the extension string.
            // This means we can avoid special-case checks for the first or last
            // extension, as well as avoid special-case checks when an extension name
            // is the same as the first part of another extension name.
            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();
    }
}