Go语言视频零基础入门到精通

aopre8

       第三部分会展示如何停止三角形的旋转以及真正做到三角形的旋转。

    我们打算能更丰富地控制旋转。为了实现它，在每一次调用onDrawFrame()时我们重设矩阵。这会重置我们的三角形的角度以使得它总是保持以初始化时设置的角度进行旋转。

java代码：
@Override

public void onDrawFrame(GL10 gl) {

// define the color we want to be displayed as the "clipping wall"

gl.glClearColor(_red, _green, _blue, 1.0f);



// 重置矩阵，使旋转速度合适

gl.glLoadIdentity();



// clear the color buffer and the depth buffer to show the ClearColor

// we called above...

gl.glClear(GL10.GL_COLOR_BUFFER_BIT);



// code snipped

}
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　　在VortexView类里移去除以10的部分以使得它旋转角度大一些.
　　_renderer.setAngle（event.getX（））；如果你尝试了，你会看到三角形根据我们触碰动作的方向进行旋转，如果你不移动手指，它就不会旋转.
　　另一个事情：我们是旋转了三角形还是旋转了整个视图？
　　为了检验，最简单的方式是创建第二个不会旋转的三角形.
　　最快也是最直接的方式就是复制并且粘贴initTriangle（）方法代码到initStaticTriangle（）方法，复制并且粘贴两个缓冲区，最后复制粘贴onDrawFrame（）函数中的最后4行代码.
　　不要忘记改变第二个三角形的颜色而且减小它的坐标以便我们能同时看到两个.我把0.5f坐标改为0.4f.下面是全部类：

java代码：
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();



private float _red = 0f;

private float _green = 0f;

private float _blue = 0f;



// a raw buffer to hold indices allowing a reuse of points.

private ShortBuffer _indexBuffer;

private ShortBuffer _indexBufferStatic;



// a raw buffer to hold the vertices

private FloatBuffer _vertexBuffer;

private FloatBuffer _vertexBufferStatic;



private short[] _indicesArray = {0, 1, 2};

private int _nrOfVertices = 3;



private float _angle;



@Override

public void onSurfaceCreated(GL10 gl, EGLConfig config) {

// preparation

gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

initTriangle();

initStaticTriangle();

}



@Override

public void onSurfaceChanged(GL10 gl, int w, int h) {

gl.glViewport(0, 0, w, h);

}



public void setAngle(float angle) {

_angle = angle;

}



@Override

public void onDrawFrame(GL10 gl) {

// define the color we want to be displayed as the "clipping wall"

gl.glClearColor(_red, _green, _blue, 1.0f);



// reset the matrix - good to fix the rotation to a static angle

gl.glLoadIdentity();



// clear the color buffer to show the ClearColor we called above...

gl.glClear(GL10.GL_COLOR_BUFFER_BIT);



// 绘制静态三角形

gl.glColor4f(0f, 0.5f, 0f, 0.5f);

gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBufferStatic);

gl.glDrawElements(GL10.GL_TRIANGLES, _nrOfVertices, GL10.GL_UNSIGNED_SHORT, _indexBufferStatic);



// 设置非静态三角形的旋转

gl.glRotatef(_angle, 0f, 1f, 0f);



gl.glColor4f(0.5f, 0f, 0f, 0.5f);

gl.glVertexPointer(3, GL10.GL_FLOAT, 0, _vertexBuffer);

gl.glDrawElements(GL10.GL_TRIANGLES, _nrOfVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer);



}



private void initTriangle() {

// float has 4 bytes

ByteBuffer vbb = ByteBuffer.allocateDirect(_nrOfVertices * 3 * 4);

vbb.order(ByteOrder.nativeOrder());

_vertexBuffer = vbb.asFloatBuffer();



// short has 4 bytes

ByteBuffer ibb = ByteBuffer.allocateDirect(_nrOfVertices * 2);

ibb.order(ByteOrder.nativeOrder());

_indexBuffer = ibb.aSSHortBuffer();



float[] coords = {

-0.5f, -0.5f, 0f, // (x1, y1, z1)

0.5f, -0.5f, 0f, // (x2, y2, z2)

0f, 0.5f, 0f // (x3, y3, z3)

};



_vertexBuffer.put(coords);



_indexBuffer.put(_indicesArray);



_vertexBuffer.position(0);

_indexBuffer.position(0);

}



private void initStaticTriangle() {

// float has 4 bytes

ByteBuffer vbb = ByteBuffer.allocateDirect(_nrOfVertices * 3 * 4);

vbb.order(ByteOrder.nativeOrder());

_vertexBufferStatic = vbb.asFloatBuffer();



// short has 4 bytes

ByteBuffer ibb = ByteBuffer.allocateDirect(_nrOfVertices * 2);

ibb.order(ByteOrder.nativeOrder());

_indexBufferStatic = ibb.asShortBuffer();



float[] coords = {

-0.4f, -0.4f, 0f, // (x1, y1, z1)

0.4f, -0.4f, 0f, // (x2, y2, z2)

0f, 0.4f, 0f // (x3, y3, z3)

};



_vertexBufferStatic.put(coords);



_indexBufferStatic.put(_indicesArray);



_vertexBufferStatic.position(0);

_indexBufferStatic.position(0);

}



public void setColor(float r, float g, float b) {

_red = r;

_green = g;

_blue = b;

}

}
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系列之Android 游戏教程（一）的帖子链接http://www.eoeandroid.com/thread-102096-1-1.html
系列之Android 游戏教程（二）的帖子链接http://www.eoeandroid.com/thread-102097-1-1.html
系列之Android 游戏教程（四）的帖子链接http://www.eoeandroid.com/thread-103115-1-1.html
系列之Android 游戏教程（五）的帖子链接http://www.eoeandroid.com/thread-103118-1-1.html
系列之Android 游戏教程（六）的帖子链接http://www.eoeandroid.com/thread-103121-1-1.html
系列之Android 游戏教程（七）的帖子链接http://www.eoeandroid.com/thread-103125-1-1.html