David, Chris,
Thanks a lot for your help.
For the moment, I have applied an offset to the roads.
When the ViewingPlafform is close to the terrain, there is no problem, but
when I have an aereal view of the scene, I get again the problem of the
Z-buffer.
I haven't already tried Chris's solution, about Dinamic Z-Buffer, when I'll
try I'll report it to the list.
Regards, Alvaro
I have apply an offset to the roads, and
-----Mensaje original-----
De: Yazel, David J. <[EMAIL PROTECTED]>
Para: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Fecha: martes 22 de mayo de 2001 16:50
Asunto: Re: [JAVA3D] Z-BUFFER PROBLEM????
>Yep, laying down roads over terrain is a nasty problem. This is especially
>true if you are using a different "road" geometry. You need to create
>co-planar geometry which can be done a variety of ways. One way is to
build
>your geometry for the road using the same heightmap source as the terrain
>itself, then sub-divide the mesh pieces until they can conform to the
>geometry undulations of the terrain geometry. Once you have a roughly
>co-planar geometry you can do to different techniques:
>
>1. Put the terrain and the road into an ordered group and have the road
>ignore the zbuffer when drawing. This will then have the road geometry
>override the zbuffer values put down by the terrain. This will work
>depending on your freedom of camera movement, since a path snaking behind a
>hill will be seen through the hill.
>
>2. The other trick is to change the PolygonAttributes of the road to have a
>PolygonOffset of some small amount which will cause the road to be
logically
>"closer" to the camera in terms of its depth testing. This only works if
>the terrain is very close to coplanar. And the amount of the polygon
offset
>and factors needs to be enough to resolve zbuffer fighting, so thats
>dependant on your clip. If the clip is 2 and 2000, then you can probably
>use a very small PolygonOffset.
>
>Dave Yazel
>www.cosm-game.com
>
>-----Original Message-----
>From: ChrisThorne [mailto:[EMAIL PROTECTED]]
>Sent: Tuesday, May 22, 2001 8:52 AM
>To: [EMAIL PROTECTED]
>Subject: Re: [JAVA3D] Z-BUFFER PROBLEM????
>
>
>Yep it's the Z buffer tearing problem again.
>Have a look at the ViewNavigationBehavior mod I sent to the list
>under the title "Test program (fwd) for Grafic card question"
>it has a solution to this (or a least Desiree's similar) problem. Hopefully
>it will work for you
>(maybe with some tweaking). I will do a more general solution later.
>
>The changes I made worked forDesiree's example but not for her main
>application, so I will
>look at it all again :(. I tried to get away without the performance
>overhead of a sqrt function
>- maybe we will have to put up with it.
>
>Essentially the solution is to provide an adaptive high precision clipping
>window around your model
>which changes as you move around. You may have to make sure there is a bit
>of distance
>between your road and terrain.
>Alternatively, I know David Yazel can do good roads on terrain - perhaps he
>can tell you how he does it :).
>
>Otherwise, if you can send me a sample program I can take a look at it,
>
>Chris
>
>alvaro zabala wrote:
>
>> I have a scene, with a terrain wich has land uses, electric towers,
>> catenarys, etc
>> I want to add a road over the terrain, with a triangleStripArray , but
I'm
>> having problems with the Z-BUFFER.
>> I fixed the front and back clipping distances to 2 and 5500 (5500/2<3000)
>>
>> Please see the atachments.
>>
>> Anyone can explains it??
>>
>>
>---------------------------------------------------------------------------
-
>----------------------------------------------------
>> Name: Prueba1.gif
>> Prueba1.gif Type: GIF Image (image/gif)
>> Encoding: base64
>>
>> Name: Prueba2.gif
>> Prueba2.gif Type: GIF Image (image/gif)
>> Encoding: base64
>
>--
> ,--_|\
> / Oz \
>Chris Thorne :)_.--._/
>[EMAIL PROTECTED] v
>
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