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From: slevy@poincare.geom.umn.edu (Stuart Levy)
Subject: Re: Fastest way to find world -> screen mapping
Message-ID: <1991Jun6.054818.29804@cs.umn.edu>
Keywords: transform world coords screen coords matrix inversion
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References: <1991Jun4.031535.18607@resmel.bhp.com.au> <1991Jun4.235906.4447@odin.corp.sgi.com>
Date: Thu, 6 Jun 91 05:48:18 GMT
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In article <1991Jun4.235906.4447@odin.corp.sgi.com> kurt@cashew.asd.sgi.com (Kurt Akeley) writes:
>In article <1991Jun4.031535.18607@resmel.bhp.com.au>, tim@resmel.bhp.com.au (Tim Monks) writes:
>|> What is the fastest way of mapping (x,y,z) (world coords) to (sx,sy)
>|> (screen coords) on a SG?
>|> ...
>
>[stuff deleted]
>
>If the result of an operation is intended for anything other than the
>framebuffer, it is NOT the job of the graphics hardware to do it.  The
>best way to transform points is to write code that transforms them on
>the MIPS processor.
>
>If the transform is from world (object) coordinates to screen coordinates,
>no matrix inversion is required.
>
>-- Kurt

I've wanted to do this too, with yes, destination being the frame buffer.
This may not be what Mr. Monks has in mind, but for example what is
the easiest way to draw a "wide point" -- a blob of fixed screen-space
size, in the location appropriate for a 3-space point, and hidden by
surfaces in front of it?  GL supports wide lines directly but I don't find
anything similar for points.  Single-pixel points can be hard to see,
especially on video.

    Stuart Levy, Geometry Center, University of Minnesota
    slevy@geom.umn.edu