[gl4java-usergroup] Drawing to an offscreen buffer silently

[Alban C. <aco...@mi...>]

Hi,

When I ask gl4java the count of available auxiliary buffers,=20
It returns 0.

gl.glGetIntegerv(gl.GL_AUX_BUFFERS, numbuff);

Does anyone know if auxiliary buffers are activated by default, if they
can be activated, or if I get 0 buffers because my OpenGL implementation
(nvidia, win32) would not support auxiliary buffers ?

I'm implementing color picking. It's done, it works, but my screen
flashes (a tenth of second, showing my drawn colors) because it looks
like it is drawing on a buffer used by OpenGL for display, though I'm
drawing my objects into the left buffer (because I don't have any
auxiliary buffers).

Here is the code (a bit simplified for ease of reading):

//switch to an offscreen buffer. Left buffer should be=20
//available in any implementation since it is mandatory=20
gl.glDrawBuffer(gl.GL_LEFT);
gl.glReadBuffer(gl.GL_LEFT);
//make sure the buffer can be written
gl.glColorMask(true,true,true,true);
           =20
//clean the buffer
gl.glClear(gl.GL_COLOR_BUFFER_BIT);

//draw our objects in plain red color
drawObjects();

//look for color under the mouse            =20
gl.glReadPixels(nextX,canvasSize().height-yMouseCoordinate,1,1,gl.GL_RED
,gl.GL_UNSIGNED_BYTE,pickedColor);
           =20
processPickedColorAndTellMeWhatObjectHasBeenPicked(pickedColor);
           =20
//switch back to regular display buffer=20
gl.glReadBuffer(gl.GL_BACK);
gl.glDrawBuffer(gl.GL_BACK);


Anyone has an idea of what could go wrong with those buffers ?

Thanks,

Alban Cousini=E9

MIND2MACHINE
http://www.mind2machine.com
=20