On Tue, 2009-09-01 at 01:01 +0000, jiangwei zhou wrote: > we know that at present the clutter's clipping is implemented in > clip plane/stencil buffer/Scissor. > > using stencil buffer, we can implement arbitrarily ploygonous > clipping. it is one very common way to do the clipping in gles. > > but now ,we have a new demand to implement the clipping without > stencil buffer . because in our target the clipping based on stencil > buffer is very slow, unacceptable. > > we consider two ways. i hope other guys can give me some suggestion > or new idear. > > 1. if only rect clipping is considered,can i clip the actor in > fragment shader? > > the clip arear is in object coordinates, can i in fragment > shader , convert the fragment coord point from clip coordinates to > object coordiantes ,then using rect including algorthim to discard > those not in the area?
If the clip region is a rectangle, Cogl should already automatically use glScissor (if possible) or the clip planes if it is not a screen rectangle. I think the clip planes and scissor rect should be quite fast so there probably isn't any benefit to using a fragment shader in this case. Also as far as I understand, using 'discard' on a lot of GLES2 hardware is not recommended so it may even end up slower than the stencil buffer. Regards, - Neil -- To unsubscribe send a mail to clutter+unsubscr...@o-hand.com
