> > With the rest I disagree. The Kyro, for example, has some high-speed local > > memory (cache) it uses to hold the pixels for a tile. It can antialias and > > render translucent scenes without ever blitting the cache to the framebuffer > > more than once. > > It can't have infinite storage for tile information - so there would have to > be a hard limit on the number of translucent/edge/intersecting tiles - that > would not be OpenGL compliant.
Each tile has a list of all polygons that might be drawn on its pixel cache. For a hardware implementation, memory could become an issue. If memory gets tight, the implementation could render all polygons currently in its tile lists and clear out tile memory. This would trade off memory space for a bit of overdraw. For a software implementation this would really not be a problem. > > This is the advantage to tile-based rendering. Since you > > only need to hold a tile's worth of pixels, you can use smaller high-speed > > cache. > > Only if the number of visible layers is small enough. What does the number of visible layers have to do with the ability to break down processing to a per-tile basis? I am not following here. > > As far as the reading of pixels from the framebuffer, this is a highly > > inefficient thing to do, no matter the hardware. If you want a fast > > application you will not attempt to read from the video card's memory. > > These operations are always extremely slow. > > They are only slow if the card doesn't implement them well - but there > are plenty of techniques (eg impostering) that rely on this kind of thing. This will always be slow. AGP transfers are inherently slow compared to everything else. DMA transfers are usually used for writing to the video card, usually passing it vertices and textures. These transfers can be done in the background. How many video cards implement DMA transfers for reads from the video card? Even if this was done, most of the time you are waiting for the results of the read in order to perform another operation. What good is pushing something into the background when you must wait for that operation to complete? These slow transfers and all the waiting makes this an extremely slow process. It is not recommended. -Raystonn _______________________________________________ Dri-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/dri-devel
