Android的OpenGL学习笔记（5）

                                                                  Android的OpenGL学习笔记（5）

接着前面的知识学习，现在可以做一个3D的图形了，和以往一样，必要的解释都在注释中：

VortexRenderer.java代码：

package com.droidnova.android.games.vortex;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;

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

import android.opengl.GLSurfaceView;

public class VortexRenderer implements GLSurfaceView.Renderer {
    private static final String LOG_TAG = VortexRenderer.class.getSimpleName();

    // a raw buffer to hold indices allowing a reuse of points.
    private ShortBuffer _indexBuffer;

    // a raw buffer to hold the vertices
    private FloatBuffer _vertexBuffer;

    // a raw buffer to hold the colors
    private FloatBuffer _colorBuffer;

    private int _nrOfVertices = 0;

    private float _xAngle;
    private float _yAngle;

    @Override
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        // preparation
        // enable the differentiation of which side may be visible
        gl.glEnable(GL10.GL_CULL_FACE);// enable了culling面，以保证只有一面。
        // which is the front? the one which is drawn counter clockwise
        gl.glFrontFace(GL10.GL_CCW);// GL_CCW表示逆时针,定义了哪种顺序为前面。GL_CW表示逆时针
        // which one should NOT be drawn
        gl.glCullFace(GL10.GL_BACK);// 设置其为GL_BACK以保证只显示正面.这或许有点迷糊偶，
        // 你可以看看如果用GL_FRONT_AND_BACK会发生什么……你将什么也看不到。

        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);//允许设置顶点
        gl.glEnableClientState(GL10.GL_COLOR_ARRAY);//允许设置顶点颜色

        initTriangle();
    }

    @Override
    public void onSurfaceChanged(GL10 gl, int w, int h) {
        gl.glViewport(0, 0, w, h);
    }

    public void setXAngle(float angle) {
        _xAngle = angle;
    }

    public float getXAngle() {
        return _xAngle;
    }

    public void setYAngle(float angle) {
        _yAngle = angle;
    }

    public float getYAngle() {
        return _yAngle;
    }

    @Override
    public void onDrawFrame(GL10 gl) {
        // define the color we want to be displayed as the "clipping wall"
        gl.glClearColor(0f, 0f, 0f, 1.0f);

        // reset the matrix - good to fix the rotation to a static angle
        gl.glLoadIdentity();

        // clear the color buffer and the depth buffer to show the ClearColor
        // we called above...
        gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

        // set rotation
        gl.glRotatef(_xAngle, 1f, 0f, 0f);
        gl.glRotatef(_yAngle, 0f, 1f, 0f);

        // gl.glColor4f(0.5f, 0f, 0f, 0.5f);
        gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBuffer);
        gl.glColorPointer(4, GL10.GL_FLOAT, 0, _colorBuffer);
        gl.glDrawElements(GL10.GL_TRIANGLES, _nrOfVertices,
                GL10.GL_UNSIGNED_SHORT, _indexBuffer);
    }

    private void initTriangle() {
        float[] coords = {
                -0.5f, -0.5f, 0.5f, // 0
                0.5f, -0.5f, 0.5f, // 1
                0f, -0.5f, -0.5f, // 2
                0f, 0.5f, 0f, // 3
        };
        _nrOfVertices = coords.length;

        float[] colors = {
                1f, 0f, 0f, 1f, // point 0 red
                0f, 1f, 0f, 1f, // point 1 green
                0f, 0f, 1f, 1f, // point 2 blue
                1f, 1f, 1f, 1f, // point 3 white
        };

        short[] indices = new short[] {
                0, 1, 3, // rwg
                0, 2, 1, // rbg
                0, 3, 2, // rbw
                1, 2, 3, // bwg
        };

        // float has 4 bytes, coordinate * 4 bytes
        ByteBuffer vbb = ByteBuffer.allocateDirect(coords.length * 4);
        vbb.order(ByteOrder.nativeOrder());
        _vertexBuffer = vbb.asFloatBuffer();

        // short has 2 bytes, indices * 2 bytes
        ByteBuffer ibb = ByteBuffer.allocateDirect(indices.length * 2);
        ibb.order(ByteOrder.nativeOrder());
        _indexBuffer = ibb.asShortBuffer();

        // float has 4 bytes, colors (RGBA) * 4 bytes
        ByteBuffer cbb = ByteBuffer.allocateDirect(colors.length * 4);
        cbb.order(ByteOrder.nativeOrder());
        _colorBuffer = cbb.asFloatBuffer();

        _vertexBuffer.put(coords);
        _indexBuffer.put(indices);
        _colorBuffer.put(colors);

        _vertexBuffer.position(0);
        _indexBuffer.position(0);
        _colorBuffer.position(0);
    }
}

VortexView.java代码：

package com.droidnova.android.games.vortex;

import android.content.Context;
import android.opengl.GLSurfaceView;
import android.view.MotionEvent;

public class VortexView extends GLSurfaceView {
    private static final String LOG_TAG = VortexView.class.getSimpleName();
    private VortexRenderer _renderer;
    private float _x = 0;
    private float _y = 0;
    private float _z = 0;

    public VortexView(Context context) {
        super(context);
        _renderer = new VortexRenderer();
        setRenderer(_renderer);
    }

    public boolean onTouchEvent(final MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
            _x = event.getX();
            _y = event.getY();
        }
        if (event.getAction() == MotionEvent.ACTION_MOVE) {
            final float xdiff = (_x - event.getX());
            final float ydiff = (_y - event.getY());
            queueEvent(new Runnable() {
                public void run() {
                    _renderer.setXAngle(_renderer.getXAngle() + ydiff);
                    _renderer.setYAngle(_renderer.getYAngle() + xdiff);
                }
            });
            _x = event.getX();
            _y = event.getY();
        }
        return true;
    }
}

最终效果图：