Depending on my setting for object mesh detail and my camera distance, I've seen as many as 18 polygons on a single flat surface of a cube when viewed in wireframe mode. Could these provide the necessary polygons to support the "naive solution"?
On Fri, Jan 16, 2009 at 7:42 AM, Soft <[email protected]> wrote: > On Fri, Jan 16, 2009 at 8:50 AM, Carlo Wood <[email protected]> wrote: > > Would this solve the simple problems that I ran into? > > For example: > > > > A house (with four walls), each wall is nearly opaque, but > > they contain an alpha channel (for a few very small windows). > > If you stand outside and rotate around a bit, you see walls > > that are *behind* the wall that you're standing in front of > > first, as if big parts of the wall that your standing in front > > of don't exist. > > > > Or, I have a house where a part has floor-to-ceiling windows, > > with a stripe (in the texture) every 2 meters or so to 'support' > > the glass. If I put an Xmas tree in my livingroom that is > > partly transparent, at some angles (most of the angles actually) > > you see those stripes in full through the tree - as if the tree > > wasn't there at all. > > > > I've never understood why this ordering bug exists; because > > I can't think of a reason that makes it hard to get it right :p. > > Can someone explain what the problem/reason is for these "features"? > > Yes, clip mapping would solve that problem at the expense of not being > able to have partially transparent pixels. > > Efficiently sorting polys with alpha surfaces is actually an unsolved > problem in computer graphics. To understand why, make two walls out of > glass in SL and then arrange them so they intersect to form an X when > seen from overhead. Now, look at the pair from the north, south, east > or west side, and ask yourself which wall is in front. The answer is > neither... or both. > > One naive solution is dividing objects in half wherever two planes > intersect, but even a few dozen prims could degenerate into tens of > millions of new surfaces with this approach. That X would turn two > surfaces into four. Try a tic-tac-toe board, #, and four surfaces > becomes twelve. Add just two more lines and the twelve becomes twenty > four. Follow that trend and imagine what it does to memory and > performance. > _______________________________________________ > Policies and (un)subscribe information available here: > http://wiki.secondlife.com/wiki/SLDev > Please read the policies before posting to keep unmoderated posting > privileges >
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