• Join Us |
  • |
  • Sign in with:

Old Carmack Ramblings

by Steve Gibson, Mar 16, 2002 7:08am PST
Related Topics – Hardware (PC only), John Carmack

If you're feeling nerdy, NVidia has published a little paper from John Carmack from a couple years back when he was working on the early new DOOM technology.


Read all the News


Comments

19 Threads | 29 Comments
  • #20
    Refresh Thread
    By: Sebastian Sylvan x
    Reply
    Oh and a correction: This wasn't pre-DOOM it was post-Q2. Also it wasn't a paper it was personal correspondence with Kilgard.

    As a side-note the new revolutionizing technique (also known as "Carmack's reverse") was first invented by Bill Bilodeau. Carmack just hadn't heard about it and sort of re-invented it backwards. Basically what it means is that you "trace" from infinity to the first visible point instead of tracing from the camera to the first visible point. Thus you eliminate problems with the near clipping plane slicing the shadow volumes.
    Mar 16, 2002 3:13pm PST
  • #14
    Refresh Thread
    By: futtbucker x
    Reply
    John C. says: "Stencil shadows still aren't cheap by any means. It can cost 3x the
    triangle count of the source model (although <2x with some optimizations is
    reasonable) per shadowing light, and it can have pathological fill rate
    utilization in some cases, like a light shining out horizontally through a
    jail cell door. Still, they are quick operations even if there are a lot
    of them. The vertexes are just bare xyz points without texcoords or color,
    and the fill rate is only to the depth/stencil buffer."

    I think he's got it backwards. The triange count of the source model and stencil shadows are patholoically filled, however it utilization in jail cells is hardly horizontally stenciled. Textcoords and vertexes vary inversely with the confundity of the xyz depth/stencil operating fillrate/buffer zone. Bah, hit the books again John.

    Mar 16, 2002 12:44pm PST