OpenGL getting started

/**

* Entry, triangle

*/

// Custom Renderer

Class myrenderer implements Android. OpenGL. glsurfaceview. Renderer {

Private float ratio;

// When the surface layer is created

Public void onsurfacecreated (gl10 GL, eglconfig config ){

// Set the screen color

Gl. glclearcolor (0, 0, 0, 1 );

// Enable the vertex buffer.

Gl. glableclientstate (gl10.gl _ vertex_array );

}

// When the surface size is

Public void onsurfacechanged (gl10 GL, int width, int height ){

// Set the view and output area.

Gl. glviewport (0, 0, width, height );

Ratio = (float) width/(float) height;

// Matrix mode, projection matrix, OpenGL Based on State Machine

Gl. glmatrixmode (gl10.gl _ projection );

// Load the Unit Matrix

Gl. glloadidentity ();

// Intercept

Gl. glfrustumf (-1f, 1f,-ratio, ratio, 3, 7 );

}

// Drawing

Public void ondrawframe (gl10 GL ){

// Clear the color cache area

Gl. glclear (gl10.gl _ color_buffer_bit );

// Model View Matrix

Gl. glmatrixmode (gl10.gl _ modelview );

Gl. glloadidentity (); // load the Unit Matrix

// Eyex, eyey, and Eyez: coordinates of the eye

// Centerx, centery, and centerz: eye observation point.

// UPX, UPX, and UPX: Specify the eye Vector

Glu. glulookat (GL, 0, 0, 5, 0, 0, 0, 0, 1, 0 );

// Draw a triangle

// Draw an array

// Triangle coordinates

Float [] coords = {

0f, ratio, 2f,

-1f,-ratio, 2f,

1f,-ratio, 2f };

// Allocate byte cache space to store vertex coordinate data

Bytebuffer Ibb = bytebuffer. allocatedirect (coords. length * 4 );

// Set the order (Local Order)

Ibb. Order (byteorder. nativeorder ());

// Place the vertex coordinate Array

Floatbuffer fbb = Ibb. asfloatbuffer ();

Fbb. Put (coords );

// Locate the pointer and read the vertex data from this position

Ibb. Position (0 );

// Set the drawing color in red.

Gl. glcolor4f (1f, 0f, 0f, 1f );

// 3-dimensional point, which uses three coordinate values to represent a point

// Type: Data Type of each vertex

// Stride: 0, span.

// Ibb: Specify the vertex buffer.

Gl. glvertexpointer (3, gl10.gl _ float, 0, Ibb );

// Draw a triangle

// 0: start point:

// 3: number of points to be drawn

Gl. gldrawarrays (gl10.gl _ triangles, 0, 3 );

}

}