android使用OpenGL ES定义图片形状

为了能够开发高端的图形作品，定义形状往往是第一步。使用OpenGL ES绘制图片你不需要知道OpenGL ES怎样希望你去定义图片对象。下面介绍协调系统相关的和屏幕，定义了形状，如三角形和圆形。

定义一个三角形：

OpenGL ES允许你在三维空间定义对象。

class Triangle
{

private FloatBuffer vertexBuffer;

// number of coordinates per vertex in this array

static final
int COORDS_PER_VERTEX =
3;

static float triangleCoords[]
= {
// in counterclockwise order:

0.0f,
0.622008459f,
0.0f,
// top

-0.5f,
-0.311004243f,
0.0f,
// bottom left

0.5f,
-0.311004243f,
0.0f // bottom right

};

// Set color with red, green, blue and alpha (opacity) values

float color[]
= {
0.63671875f,
0.76953125f,
0.22265625f,
1.0f };

public Triangle()
{

// initialize vertex byte buffer for shape coordinates

ByteBuffer bb =
ByteBuffer.allocateDirect(

// (number of coordinate values * 4 bytes per float)

triangleCoords.length
* 4);

// use the device hardware's native byte order

bb.order(ByteOrder.nativeOrder());

// create a floating point buffer from the ByteBuffer

vertexBuffer = bb.asFloatBuffer();

// add the coordinates to the FloatBuffer

vertexBuffer.put(triangleCoords);

// set the buffer to read the first coordinate

vertexBuffer.position(0);

}

定义一个矩形：

class Square
{

private FloatBuffer vertexBuffer;

private ShortBuffer drawListBuffer;

// number of coordinates per vertex in this array

static final
int COORDS_PER_VERTEX =
3;

static float squareCoords[]
= {
-0.5f,
0.5f,
0.0f,
// top left

-0.5f,
-0.5f,
0.0f,
// bottom left

0.5f,
-0.5f,
0.0f,
// bottom right

0.5f,
0.5f,
0.0f };
// top right

private short drawOrder[]
= {
0,
1, 2,
0,
2, 3
}; // order to draw vertices

public Square()
{

// initialize vertex byte buffer for shape coordinates

ByteBuffer bb =
ByteBuffer.allocateDirect(

// (# of coordinate values * 4 bytes per float)

squareCoords.length
* 4);

bb.order(ByteOrder.nativeOrder());

vertexBuffer = bb.asFloatBuffer();

vertexBuffer.put(squareCoords);

vertexBuffer.position(0);

// initialize byte buffer for the draw list

ByteBuffer dlb =
ByteBuffer.allocateDirect(

// (# of coordinate values * 2 bytes per short)

drawOrder.length
* 2);

dlb.order(ByteOrder.nativeOrder());

drawListBuffer = dlb.asShortBuffer();

drawListBuffer.put(drawOrder);

drawListBuffer.position(0);

}

}