Re: Crimson RE with 1 RM (and AA warning under 1.2)

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Jim Helman (jimh++at++surreal)
Mon, 19 Sep 94 18:25:29 -0700

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It isn't the size of the window, but rather the size of the
video format you are currently running. The issue at any particular
screen resolution is whether the RMs have enough frame buffer storage
to store multiple subsamples for each pixel. Use /usr/gfx/setmon to
switch to a lower resolution VOF (hopefully, you have a multisync
monitor). You can run /usr/gfx/gfxinfo to see whether you have enough
frame buffer memory for multisampling as indicated by a Medium or
Large pixel depth. 1RM ++at++ 980x760 supports medium pixel depth which
gives 8 subsamples with 1 bit of stencil and 24 bit Z. 1RM ++at++ 640x480
supports large pixels which give 16 subsamples. 1RM ++at++ 1280x1024
supports small pixels which have no subsamples and therefore no
antialiasing and no multisample transparency. The lack of multisample
transparency means 1) no fade LOD and 2) transparent objects must be
drawn back to front to blend properly, since only blended transparency
is available. You'll notice #2 in the Performer Town's trees.

WARNING ON 1.2 & ANTIALIASING: by default Performer 1.2 ONLY gives 4
subsamples per pixel on medium pixel depth configs. The change was
caused by Performer internally requesting 4 bits of stencil for pixel
fill statistics. Programs can override the default by doing their own
mssize/gconfig in the init pipe callback.

When you setup the frame buffer in your application, you can tradeoff
between Z (24 or 32) color bits (8 or 12), stencil bits and subsamples
(0, 4, 8 or 16). You do this using mssize() gconfig() under GL
windowing (always use getgconfig to check what GL decided to give you),
e.g.:
              winopen("ms");
              RGBsize(reqCol);
              RGBmode();
              zbsize(0); /* no regular Z buf */
              stensize(0); /* no regular stencil */
              mssize(reqSub, reqZ, reqSten);
              gconfig();
              printf("req: sub: %d z: %d sten: %d, col: %d\n",
                     reqSub, reqZ, reqSten, reqCol);
              printf("got: sub: %d z: %d sten: %d, col: %d\n",
                     getgconfig(GC_MS_SAMPLES),
                     getgconfig(GC_BITS_MS_ZBUFFER),

rgds,

-jim helman

jimh++at++surreal.asd.sgi.com
415/390-1151

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