Android OpenGL教程-第五课【转】

第五课 3D空间:

我们使用多边形和四边形创建3D物体，在这一课里，我们把三角形变为立体的金子塔形状，把四边形变为立方体。

先看看三角形的顶点变成啥了

private float[] mTriangleArray = {

           0.0f,1.0f,0.0f,

           -1.0f,-1.0f,1.0f,

           1.0f,-1.0f,1.0f,

           0.0f,1.0f,0.0f,

           1.0f,-1.0f,1.0f,

           1.0f,-1.0f,-1.0f,

           0.0f,1.0f,0.0f,

           1.0f,-1.0f,-1.0f,

           -1.0f,-1.0f,-1.0f,

           0.0f,1.0f,0.0f,

           -1.0f,-1.0f,-1.0f,

           -1.0f,-1.0f,1.0f

};

private FloatBuffer mTriangleBuffer;

一个四个面，每个面三个点，地面没画。

你们仔细看看每个面，都是按逆时针方向画的。当然，如果你没有增加Cull剔除代码（上节课最后提到），至于顺时针，逆时针都无所谓，都画。但是我们还是推荐使用按照方向来写的array。

三角形的颜色数组来了

private float[] mColorArray={

           1.0f,0.0f,0.0f,1.0f,

           0.0f,1.0f,0.0f,1.0f,

           0.0f,0.0f,1.0f,1.0f,

           1.0f,0.0f,0.0f,1.0f,

           0.0f,0.0f,1.0f,1.0f,

           0.0f,1.0f,0.0f,1.0f,

           1.0f,0.0f,0.0f,1.0f,

           0.0f,1.0f,0.0f,1.0f,

           0.0f,0.0f,1.0f,1.0f,

           1.0f,0.0f,0.0f,1.0f,

           0.0f,0.0f,1.0f,1.0f,

           0.0f,1.0f,0.0f,1.0f,    

};

private FloatBuffer mColorBuffer;

注意，同一个点是同一个颜色。

立方体的顶点数组：（原文中没有）

// 四边形的顶点数组
private float[] mQuadsArray = {
            // 前
            1f, 1f, 1f, // 右上
            -1f, 1f, 1f, // 左上
            -1f, -1f, 1f, // 左下
            1f, -1f, 1f,// 右下
            // 右
            1f, 1f, -1f, // 右上
            1f, 1f, 1f, // 左上
            1f, -1f, 1f, // 左下
            1f, -1f, -1f,// 右下
            // 后
            -1f, 1f, -1f, // 右上
            1f, 1f, -1f, // 左上
            1f, -1f, -1f, // 左下
            -1f, -1f, -1f,// 右下
            // 左
            -1f, 1f, 1f, // 右上
            -1f, 1f, -1f, // 左上
            -1f, -1f, -1f, // 左下
            -1f, -1f, 1f, // 右下
            // 顶
            1f, 1f, -1f, // 右上
            -1f, 1f, -1f, // 左上
            -1f, 1f, 1f, // 左下
            1f, 1f, 1f, // 右下
            // 底
            1f, -1f, 1f, // 右上
            -1f, -1f, 1f, // 左上
            -1f, -1f, -1f, // 左下
            1f, -1f, -1f // 右下
}; // 从这里可以看出，我们按照逆时针的方向画图
private FloatBuffer mQuadsBuffer;

立方体的颜色数组来了

private float[] mQuadColorArray={

       0.0f,1.0f,0.0f,1.0f,

       0.0f,1.0f,0.0f,1.0f,

       0.0f,1.0f,0.0f,1.0f,

       0.0f,1.0f,0.0f,1.0f,

       1.0f,0.5f,0.0f,1.0f,

       1.0f,0.5f,0.0f,1.0f,

       1.0f,0.5f,0.0f,1.0f,

       1.0f,0.5f,0.0f,1.0f,

       1.0f,0.0f,0.0f,1.0f,

       1.0f,0.0f,0.0f,1.0f,

       1.0f,0.0f,0.0f,1.0f,

       1.0f,0.0f,0.0f,1.0f,

       1.0f,1.0f,0.0f,1.0f,

       1.0f,1.0f,0.0f,1.0f,

       1.0f,1.0f,0.0f,1.0f,

       1.0f,1.0f,0.0f,1.0f,

       0.0f,0.0f,1.0f,1.0f,

       0.0f,0.0f,1.0f,1.0f,

       0.0f,0.0f,1.0f,1.0f,

       0.0f,0.0f,1.0f,1.0f,

       1.0f,0.0f,1.0f,1.0f,

       1.0f,0.0f,1.0f,1.0f,

       1.0f,0.0f,1.0f,1.0f,

       1.0f,0.0f,1.0f,1.0f,

};

private FloatBuffer mQuadColorBuffer;

不要晕，后面有了纹理就好了，不过这是基础，一定要掌握。

画图的代码来了

       gl.glTranslatef(-1.5f, 0.0f, -6.0f);
       gl.glRotatef(rtri, 0.0f, 1.0f, 0.0f);   //绕Y轴旋转
//     gl.glColor4f(1f, 1f, 1f, 1f);
       gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
       gl.glEnableClientState(GL10.GL_COLOR_ARRAY);  

       gl.glColorPointer(4, GL10.GL_FLOAT, 0, mColorBuffer);  

       gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mTriangleBuffer);
       gl.glDrawArrays(GL10.GL_TRIANGLES, 0, 12);     //四棱锥有4个面，每个面3个点  

       gl.glLoadIdentity();
       gl.glTranslatef(1.5f, 0.0f, -6.0f);
       gl.glRotatef(rquad, 1.0f, 0.0f, 0.0f);  // gl.glRotatef(rquad, 1.0f, -0.8f, 0.0f); // 斜着旋转

       gl.glColorPointer(4, GL10.GL_FLOAT, 0, mQuadColorBuffer);
       gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mQuadsBuffer);  

       //依次画6个面
       for (int i=0; i<6; i++){
           gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, i*4, 4);
       }  

       rtri+=0.2f;
       rquad-=0.15f;  

运行结果：

(注：本教程转自其他网页，并加以修改，查看原网页请点击这里)