Thanks, you method is a good methed.
Actually, my graphic is not so simple, I can not keep track of them.
Is there anyway that, I draw part of the picture, show it, then hold for a second, then draw the another part of the picture.
I use something like Idle and sleep, but it did not show anything untill the whole picture is drawn.
Maybe I did not use the idle method correctly, any place I can find sample codes?
It is not possible to see partial result with opengl. However, you can define a clip plane.
In case you do not know, for any clip plane, only primitives on the positive side of the clip plane, ie pos*normal of clip plane > 0,
is drawn, the rest is clipped. You can then “animate”, ie move the clip plane across space, as you render. This will allow you too slowly show the scene being draw, but actually each time it is being rendered, but a larger and larger piece of it is not being clipped.
You can define clip plane as follows:
glEnable(GL_CLIP_PLANE0);
glClipPlane( id, clipplane_eq);
where equation is just the equation of a plane.
Remember clip plane is modifed by the modelview, so be careful.