Android OpenGL教程-第五课

Android OpenGL 教程
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.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;