CubeRenderer.java

/*
 * Copyright (C) 2014 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.google.android.glass.sample.apidemo.opengl;

import com.google.android.glass.timeline.GlRenderer;

import android.opengl.GLES20;
import android.opengl.Matrix;
import android.os.SystemClock;

import java.util.concurrent.TimeUnit;
import javax.microedition.khronos.egl.EGLConfig;

/**
 * Renders a 3D OpenGL Cube on a {@link LiveCard}.
 */
public class CubeRenderer implements GlRenderer {

    /** Rotation increment per frame. */
    private static final float CUBE_ROTATION_INCREMENT = 0.6f;

    /** The refresh rate, in frames per second. */
    private static final int REFRESH_RATE_FPS = 60;

    /** The duration, in milliseconds, of one frame. */
    private static final float FRAME_TIME_MILLIS = TimeUnit.SECONDS.toMillis(1) / REFRESH_RATE_FPS;

    private final float[] mMVPMatrix;
    private final float[] mProjectionMatrix;
    private final float[] mViewMatrix;
    private final float[] mRotationMatrix;
    private final float[] mFinalMVPMatrix;

    private Cube mCube;
    private float mCubeRotation;
    private long mLastUpdateMillis;

    public CubeRenderer() {
        mMVPMatrix = new float[16];
        mProjectionMatrix = new float[16];
        mViewMatrix = new float[16];
        mRotationMatrix = new float[16];
        mFinalMVPMatrix = new float[16];

        // Set the fixed camera position (View matrix).
        Matrix.setLookAtM(mViewMatrix, 0, 0.0f, 0.0f, -4.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f);
    }

    @Override
    public void onSurfaceCreated(EGLConfig config) {
        // Set the background frame color
        GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        GLES20.glClearDepthf(1.0f);
        GLES20.glEnable(GLES20.GL_DEPTH_TEST);
        GLES20.glDepthFunc(GLES20.GL_LEQUAL);
        mCube = new Cube();
    }

    @Override
    public void onSurfaceChanged(int width, int height) {
        float ratio = (float) width / height;

        GLES20.glViewport(0, 0, width, height);
        // This projection matrix is applied to object coordinates in the onDrawFrame() method.
        Matrix.frustumM(mProjectionMatrix, 0, -ratio, ratio, -1.0f, 1.0f, 3.0f, 7.0f);
        // modelView = projection x view
        Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mViewMatrix, 0);
    }

    @Override
    public void onDrawFrame() {
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);

        // Apply the rotation.
        Matrix.setRotateM(mRotationMatrix, 0, mCubeRotation, 1.0f, 1.0f, 1.0f);
        // Combine the rotation matrix with the projection and camera view
        Matrix.multiplyMM(mFinalMVPMatrix, 0, mMVPMatrix, 0, mRotationMatrix, 0);

        // Draw cube.
        mCube.draw(mFinalMVPMatrix);
        updateCubeRotation();
    }

    /** Updates the cube rotation. */
    private void updateCubeRotation() {
        if (mLastUpdateMillis != 0) {
            float factor = (SystemClock.elapsedRealtime() - mLastUpdateMillis) / FRAME_TIME_MILLIS;
            mCubeRotation += CUBE_ROTATION_INCREMENT * factor;
        }
        mLastUpdateMillis = SystemClock.elapsedRealtime();
    }
}