Re: Terrain LOD Modeling

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Masanori Kakimoto (kaki++at++kaki.nsg.sgi.com)
Tue, 19 Mar 1996 12:01:15 +0900


You can eliminate most of the gaps by patching triangles to the edge
of each tile. The shape of each triangle is exactly the same as
the corresponding gap. In other words, the third vertex of the
triangle should be employed from the more detailed LOD tiles. (I
assume you use doubled edges for one-level detailed tile.)

To make the triangles appear only when the tile is adjecent to a
more detailed LOD tile, the triangles need to be generated
selectively. You should generate a triangle when the elevation of
the third vertex will be lower than the average of the elevations
of the other two vertices on the tile edge.

In this trick, gaps still exist where the above condition does not
meet. However it is difficult to see the background through those
gaps because more detailed LOD tiles are in most cases closer to the
viewer and they hide the remaining 50% gaps.

When you fly underground rather than in the sky, please reverse
the condition ;-)

On Mar 18, 6:43pm, Andrew C Jank wrote:
> Subject: Terrain LOD Modeling
> In my application, I am rendering terrain with several LODs, but
> between the separate terrain tiles (when the tiles differ in LOD and are
> comprised of different edge points), the background shows through at
> various locations between the tiles. I knew this would likely be a
> problem, but I am having trouble finding a simple fix for the problem,
> since as the viewpoint changes direction and location, different tiles
> would necessarily be adjacent to other tiles of varying LOD. (we are
> using Performer 1.2 on an Indigo XZ, and will not be upgrading to
> Performer 2.0 for a while).
>
> Andy
>
>
>-- End of excerpt from Andrew C Jank

-- 
Masanori Kakimoto                  mailto:kaki++at++nsg.sgi.com
East Asia Technology Network, Tokyo Office
c/o Nihon Silicon Graphics K.K.
TEL:+81-3-5488-1852  FAX:+81-3-5420-2397  Voicemail:5-7465

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