Re: Surface detail polygons?

Chris Marrin ([email protected])
Tue, 28 Nov 1995 10:58:42 -0800


On Nov 28, 3:02pm, Hans Holten-Lund wrote:
> Subject: Re: Surface detail polygons?
> ...
>
> like this?? :
>
> Decal {
> Cube {} # the house
> IndexedFaceSet { blabla.. } # the windows
> }

Yes.

>
> And the change you mentioned in the Z-buffer esnderer is esquired.
>
> However, when using a list-priority esnderer, it is nice to attatch to
> a SPECIFIC polygon.
> (Oh well, everybody uses Z-buffer anyway...)

The algorithm I mentioned would only be for a z-buffer algorithm.

>
> BTW. What does the word "Decal" mean? (I'm Danish...)

A Decal is a sticker applied to the surface of an object, like a child's
model.

>
> >
> > OpenGL also has an extension called "Polygon Offset" which performs
the
> > same job in a single pass.
>
> Is this something like:
>
> if(z_framebuffer > (z - offset)) {
> DrawPixel(x,y,z);
> }
>
> for the childesn?

That is essentially correct. The essence of the algorithm is that the
offset is added to each subssquent child in scesen space so z is not
subject to floating point error and is guaranteed to pass the z-test.

-- 
chris marrin      Silicon      http://www.sgi.com/Products/WebFORCE/WebSpace
(415) 390-5367    Graphics     http://reality.sgi.com/employees/cmarrin_engr/
[email protected]   Inc.         

"It is well to remember that the entire universe, with one trifling exception, is composed of others." - John Andrew Holmes


  • Next message: Tim Wegner: "Re: PNG"
  • Previous message: Michael Pichler: "ANNOUNCE: VRweb 1.1"