model overlap at certan distance

Hi,

Here is my problem:

I have a scene with models, cameras, textures, etc. When I export this scene i

see strange things like models that overlaps at certain distance from the

camera. I whould like to know if anyone of you had that problem before an who

you resolved it.

Many thanks in advance.

Re: model overlap at certan distance

Hi,

Yes, i think I had such a problem, Try setting the camera(from witch you are viewing) hither to a greater value.

--

w3d.camera(1).hither = 50

--

That solved my problem.

Daniel.

Re: model overlap at certan distance

And if that doesn't work, try scaling the camera by a large factor like

10-20 or so.

sprite(the currentSpriteNum).camera.scale = vector(20,20,20)

If you build the scale of the world too small it can suffer from the

Z-buffer sorting issue, especially on older cards, and enlarging the

camera's viewing frustum can compensate for it.

Cheers

Richard Smith

Re: model overlap at certan distance

Oops, sorry that should have read...

sprite(the currentSpriteNum).camera.transform.scale = vector(20,20,20)

Richard Smith

Re: model overlap at certan distance

Thanks for the quick replies. I remember that problem too danieloizo, and i

solved scaling the camera and/or playing around with hither yon values.

In this case tweaking the camera makes no diference, i've tried. By unkowledge

i didn't mention the part that the models with problems have transparency.

Fontunately i have found this thread on director-online that describes the

cause of the problem(two transparent models, see the shckwave movie whitin).

Maybe there is a way to correct this z-buffer problem, or maybe not. I leave

this thread open.

Re: model overlap at certan distance

The problem is that models which have transparent textures are sorted

per-model, by their geometric centre. Here's a detailed description of when and

why the problem occurs:

http://nuttybar.drama.uga.edu/pipermail/dir3d-l/2005-February/008031.html

The solution is to break the model down into separate parts, so that each part

is sorted by its own geometric centre.

As a demo - here are 2 cubes, each sitting on opposite sides of a long wall:

http://www.robotduck.com/models/?x=-240&y=35.00&z=40.00&t=79&a=-270&d=728.2&dir=

alphaSort&file=alphaCubesAlphaWall

Both the cubes and the wall have alpha textures with transparency. As the view

rotates, each object is sorted only by its distance from the camera, causing

the cubes to appear to 'pop' in front of and behind the wall as their geometric

centre becomes closer/further to the camera than the wall's geometric centre.

In this fixed scene, the wall has been split into 3 separate models, thereby

causing each separate piece to be sorted independantly by its geometric centre.

This reduces the chance that a cube's centre will be closer to the camera than

a wall which is supposed to occlude it.

http://www.robotduck.com/models/?x=-240&y=35.00&z=40.00&t=79&a=-270&d=728.2&dir=

alphaSort&file=alphaCubesAlphaWallSeparated

If you watch carefully however, there are still moments where the sorting is

incorrect and they overlap. This could be fixed by breaking up the wall into

still smaller sections.

Increasing the 'hither' value of the camera is not the correct solution in

this case. It is the correct solution to a different problem with overlapping

models however, called 'z-fighting' : http://en.wikipedia.org/wiki/Z-fighting

hope this helps!

- Ben

Re: model overlap at certan distance

Hi,

Very well explained duckets , It's good to know about this z-buffer problem.

Daniel