opengl - how can glFlush() affect rendering correctness? -

opengl - how can glFlush() affect rendering correctness? -

upon noticing there unexpected artefacts in other opengl programs, did digging , discovered can upgrade opengl stack on ubuntu: https://launchpad.net/~xorg-edgers/+archive/ppa

after updating, gl rendering faster (my test programs below doubled in speed!) , without artefacts.

so reply own question: how can glflush() impact rendering correctness? when drivers buggy.

=== original question ===

or, more correctly, fundamental bug classic untrendy non-shader-vbo-stuff?

cdef struct xyz: float x, y, z cdef inline void _normal(xyz b,xyz a): glnormal3f(a.x-b.x,a.y-b.y,a.z-b.z) cdef inline void _draw_quad(xyz a,xyz b,xyz c,xyz d): glvertex3f(a.x,a.y,a.z) glvertex3f(b.x,b.y,b.z) glvertex3f(c.x,c.y,c.z) glvertex3f(d.x,d.y,d.z) cdef void _draw_grid(xyz a,xyz b,xyz c,xyz d): glbegin(gl_line_loop) _draw_quad(a,b,c,d) glend() .... # main loop goes through info array issuing appropriate functions while self._buf.remaining() > 0: op = self._buf.read_char() if op == _color: col = self._buf.read_rgb() #print col glcolor3f(col.r,col.g,col.b) elif op in (_box,_grid): tl,tr,br,bl,trb,brb,tlb,blb = self._buf.read_xyz(),self._buf.read_xyz(),\ self._buf.read_xyz(),self._buf.read_xyz(),\ self._buf.read_xyz(),self._buf.read_xyz(),\ self._buf.read_xyz(),self._buf.read_xyz() if op == _box: #print "box",col glbegin(gl_quads) func = _draw_quad else: #print "grid",col func = _draw_grid _normal(tlb,tl) func(tl,tr,br,bl) _normal(tl,tr) func(tr,trb,brb,br) _normal(tr,tl) func(tl,tlb,blb,bl) _normal(tr,tl) func(tl,tlb,trb,tr) _normal(tl,tr) func(bl,blb,brb,br) _normal(tl,tlb) func(tlb,trb,brb,blb) if op == _box: glend() #glflush() else: raise exception("corrupt serialisation; got %x"%op)

if flush after each cube or wireframe, correct rendering:

if omit flush - , don't want flushing, if not treading optimal opengl path - incorrect rendering, , bug don't understand:

for curious, here how glutsolidcube , wires it: http://www.google.com/codesearch/p?hl=en#xbii4fg5bfw/trunk/fds/trunk/smv_5/source/glut-3.7.6/glut_shapes.c&q=glutsolidcube%20lang:c&sa=n&cd=4&ct=rc

i can't exactly why not calling glflush() causes undesired results, may want take @ question difference between glflush advertisement glfinish asked time ago. may have useful info.

as solutions, perhaps seek putting glflush() after you're done rendering entire scene, opposed each cube.

opengl cython