# 定义形状

## 定义三角形

### Kotlin

```// number of coordinates per vertex in this array
const val COORDS_PER_VERTEX = 3
var triangleCoords = floatArrayOf(     // 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
)

class Triangle {

// Set color with red, green, blue and alpha (opacity) values
val color = floatArrayOf(0.63671875f, 0.76953125f, 0.22265625f, 1.0f)

private var vertexBuffer: FloatBuffer =
// (number of coordinate values * 4 bytes per float)
ByteBuffer.allocateDirect(triangleCoords.size * 4).run {
// use the device hardware's native byte order
order(ByteOrder.nativeOrder())

// create a floating point buffer from the ByteBuffer
asFloatBuffer().apply {
// add the coordinates to the FloatBuffer
put(triangleCoords)
// set the buffer to read the first coordinate
position(0)
}
}
}
```

### Java

```public 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);
}
}
```

## 定义方形

### Kotlin

```// number of coordinates per vertex in this array
const val COORDS_PER_VERTEX = 3
var squareCoords = floatArrayOf(
-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
)

class Square2 {

private val drawOrder = shortArrayOf(0, 1, 2, 0, 2, 3) // order to draw vertices

// initialize vertex byte buffer for shape coordinates
private val vertexBuffer: FloatBuffer =
// (# of coordinate values * 4 bytes per float)
ByteBuffer.allocateDirect(squareCoords.size * 4).run {
order(ByteOrder.nativeOrder())
asFloatBuffer().apply {
put(squareCoords)
position(0)
}
}

// initialize byte buffer for the draw list
private val drawListBuffer: ShortBuffer =
// (# of coordinate values * 2 bytes per short)
ByteBuffer.allocateDirect(drawOrder.size * 2).run {
order(ByteOrder.nativeOrder())
asShortBuffer().apply {
put(drawOrder)
position(0)
}
}
}
```

### Java

```public 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);
}
}
```

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