OpenGL draws the pyramid and removes it.

/**
* Buffer tool class
*/
Public class bufferutil {
/**
* Convert a floating point group to a byte Buffer
*/
Public static bytebuffer arr2bytebuffer (float [] ARR ){
Bytebuffer Ibb = bytebuffer. allocatedirect (ARR. length * 4 );
Ibb. Order (byteorder. nativeorder ());
Floatbuffer fbb = Ibb. asfloatbuffer ();
Fbb. Put (ARR );
Ibb. Position (0 );
Return Ibb;
}
 
/**
* Convert list to byte Buffer
*/
Public static bytebuffer list2bytebuffer (list <float> List ){
Bytebuffer Ibb = bytebuffer. allocatedirect (list. Size () * 4 );
Ibb. Order (byteorder. nativeorder ());
Floatbuffer fbb = Ibb. asfloatbuffer ();
For (float F: List ){
Fbb. Put (f );
}
Ibb. Position (0 );
Return Ibb;
}
}

/**

* Renderer

*/

Public abstract class abstractmyrenderer implements Android. OpenGL. glsurfaceview. Renderer

{

Private float ratio;

Public float xrotate = 0f; // rotation angle around the X axis

Public float yrotate = 0f; // rotate the angle around the X axis

/**

* 1.

*/

Public void onsurfacecreated (gl10 GL, eglconfig config)

{

// Clear color

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

// Enable the vertex buffer Array

Gl. glableclientstate (gl10.gl _ vertex_array );

}

/**

* 2.

*/

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

// Set the viewport

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

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

// Projection Matrix

Gl. glmatrixmode (gl10.gl _ projection );

// Load the Unit Matrix

Gl. glloadidentity ();

// Set the intercept

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

/**

* 3.

*/

Public abstract void ondrawframe (gl10 GL );

}

 

**

* Pyramid, square

*/

Public class mytriangleconerenderer extends actmyrenderer {

Public void onsurfacecreated (gl10 GL, eglconfig config ){

Gl. glclearcolor (0f, 0f, 0f, 1f );
// Vertex buffer
Gl. glableclientstate (gl10.gl _ vertex_array );
// Enable color Buffer
Gl. glableclientstate (gl10.gl _ color_array );
}
 
Public void ondrawframe (gl10 GL ){
// Clear the color buffer and depth buffer
Gl. glclear (gl10.gl _ color_buffer_bit | gl10.gl _ depth_buffer_bit );
// Set the drawing color
Gl. glcolor4f (1f, 0f, 0f, 1f );

// Enable deep Test
Gl. glable (gl10.gl _ depth_test );

// Enable Surface Removal
Gl. glable (gl10.gl _ cull_face );
// Specify the preceding ()
// CCW: counter clock wise --> counter-clockwise
// Cw: clock wise --> clockwise
Gl. glfrontface (gl10.gl _ CCW );
// Remove the back
Gl. glcullface (gl10.gl _ Back );

// Gl10.gl _ smooth: Smooth coloring (default)
// Gl10.gl _ flat: monotonous mode
Gl. glshademodel (gl10.gl _ flat );

// Operation Model View Matrix
Gl. glmatrixmode (gl10.gl _ modelview );
Gl. glloadidentity ();
// Set eye Parameters
Glu. glulookat (GL, 0f, 0f, 5f, 0f, 0f, 0f, 0f, 1f, 0f );

// Rotation Angle
Gl. glrotatef (xrotate, 1, 0, 0 );
Gl. glrotatef (yrotate, 0, 1, 0 );

// Calculate the coordinate of a vertex
Float r = 0.5f; // radius
Float x = 0f, y = 0f, Z =-0.5f;

****************** ******/
// Vertex coordinate set
List <float> coordslist = new arraylist <float> ();
// Add a cone vertex
Coordslist. Add (0f );
Coordslist. Add (0f );
Coordslist. Add (0.5f );

// Vertex Color Set
List <float> colorlist = new arraylist <float> ();
Colorlist. Add (1f); // R
Colorlist. Add (0f); // G
Colorlist. Add (0f); // B
Colorlist. Add (1f); //

****************** ******/
// Cone Coordinate
List <float> coordsconebottomlist = new arraylist <float> ();
Coordsconebottomlist. Add (0f );
Coordsconebottomlist. Add (0f );
Coordsconebottomlist. Add (-0.5f );

Boolean flag = false;
// Bottom
For (float alpha = 0f; Alpha <math. Pi * 6; alpha = (float) (alpha + math. PI/8 )){
// Cone
X = (float) (R * Math. Cos (alpha ));
Y = (float) (R * Math. Sin (alpha ));
Coordslist. Add (X );
Coordslist. Add (y );
Coordslist. Add (z );

// Cone Coordinate
Coordsconebottomlist. Add (X );
Coordsconebottomlist. Add (y );
Coordsconebottomlist. Add (z );

// Vertex color value
If (flag =! Flag ){
// Yellow
Colorlist. Add (1f );
Colorlist. Add (1f );
Colorlist. Add (0f );
Colorlist. Add (1f );
}
Else {
// Red
Colorlist. Add (1f );
Colorlist. Add (0f );
Colorlist. Add (0f );
Colorlist. Add (1f );
}
}
// Vertex color value
If (flag =! Flag ){
// Yellow
Colorlist. Add (1f );
Colorlist. Add (1f );
Colorlist. Add (0f );
Colorlist. Add (1f );
}
Else {
// Red
Colorlist. Add (1f );
Colorlist. Add (0f );
Colorlist. Add (0f );
Colorlist. Add (1f );
}

// Color Buffer
Bytebuffer colorbuffer = bufferutil. list2bytebuffer (colorlist );
Gl. glcolorpointer (4, gl10.gl _ float, 0, colorbuffer );
// Draw the cone
Gl. glvertexpointer (3, gl10.gl _ float, 0, bufferutil. list2bytebuffer (coordslist ));
Gl. gldrawarrays (gl10.gl _ triangle_fan, 0, coordslist. Size ()/3 );

// Remove the front
Gl. glcullface (gl10.gl _ front );
// Draw the cone
Colorbuffer. Position (4 );
Gl. glcolorpointer (4, gl10.gl _ float, 0, colorbuffer );
Gl. glvertexpointer (3, gl10.gl _ float, 0, bufferutil. list2bytebuffer (coordsconebottomlist ));
Gl. gldrawarrays (gl10.gl _ triangle_fan, 0, coordsconebottomlist. Size ()/3 );
}
}

// Main Interface

Public class mainactivity extends activity {

Private abstractmyrenderer render;

Private myglsurfaceview view;

Public void oncreate (bundle savedinstancestate ){

Super. oncreate (savedinstancestate );

View = new glsurfaceview (this );

Render = new mytriangleconerenderer ();

View. setrenderer (render );

// Glsurfaceview. rendermode_continuously: continuous rendering (default)

// Glsurfaceview. rendermode_when_dirty: Dirty rendering, command rendering

View. setrendermode (glsurfaceview. rendermode_when_dirty );

Setcontentview (View );

}

Public Boolean onkeydown (INT keycode, keyevent event ){

Float step = 5f;

// Up

If (keycode = keyevent. keycode_dpad_up ){

Render. xrotate = render. xrotate-step;

} Else if (keycode = keyevent. keycode_dpad_down ){

Render. xrotate = render. xrotate + step;

} Else if (keycode = keyevent. keycode_dpad_left ){

Render. yrotate = render. yrotate + step;

} Else if (keycode = keyevent. keycode_dpad_right ){

Render. yrotate = render. yrotate-step;

}

// Request rendering, used with dirty Rendering

View. requestrender ();

Return super. onkeydown (keycode, event );

}

}