Front Clipping Plane - Z fighting

[lbuttery]

In prior threads Doug has mentioned changing the front clipping plane to control/eliminate Z-fighting when working with large models or site plans


Can someone explain where I can find this setting and what I should set it to

I found a setting the the Camera defaults that was set to 300" and I tried 100" and then 48" but it had no effect ???

I am using the Perspective Full Overview camera

Shortly I will be adding 3 more buildings to this campus

I have set the origin of each building model to 0,0,0 and the site plan to 0,0,0

Currently, these symbols were made using the .3ds export/import method
would using models created the internal chief method help ???

Lew

[perryh]

I see roofing, Z-fighting, just make your roofing layer thicker in the roof Dbx.

[Dermot Dempsey]

Z-fighting can happen in any 3D graphics program that uses a "depth buffer" to determine which surfaces are in front of other surfaces. I won't explain how it works under the hood because it is probably more information then most people want to know.

The basic problem is that the program can't easily determine which surface is in front so they "fight" and you can have random pieces of one surface or another appear on your screen. As you move the camera around, different surfaces or different parts of surface will randomly win the fight and appear on your screen.

You can create a z-fighting problem at any time you want by creating two objects that overlap each other. In the attached picture, I have two cabinet soffits that overlap so that the surfaces occupy the same space. They are using two different materials so it is obvious that there is a problem. There is really no practical way to solve this problem.

Some times you will get z-fighting problem with surfaces that don't overlap but are very "close" to each other. How close the surfaces can be and when you will start to have problems is not easy to determine. This is dependent on your video card and inexpensive video cards may have more problems then better ones. Mostly this is dependent on the data within your model. For example, if your model has two surfaces that are close you may only see a problem if you are zoomed way out but not when your camera is close to the surfaces.

One common reason for seeing z-fighting is that your model has an object or surface that is very far away from the rest such as when you accidently move an object way out into space or you have a bad surface shooting out into space. To solve this problem, you should remove the wayward object or fix the model to prevent the surface that is shooting out.

Another common reason for seeing z-fighting is because your model has surfaces that are close to each other (such as wall surfaces or roof surfaces) and your camera is far from them (such as doing an overview) and the model has surfaces that are both near and far from the camera (like when you have terrain displaying).

In situations like this, you can sometimes solve the problem by adjusting your camera settings. The camera setting that has the most affect on this problem is the "Clip Surfaces Within" setting. This value will change what we refer to as your "front" or "near clipping plane". Normally, this setting is set to 24" by default which means any surfaces that are within 2' of the camera will be "clipped" so that they will not appear on your screen. If you are having a z-fighting problem, you should try increasing your Clip Surfaces Within. Try changing it from 2' to 4'. If this does not solve the problem, try changing it from 4' to 8'. If this does not solve the problem, try changing it from 8' to 16'.

If increasing this value does not eventually solve the problem, then you may need to modify the actual model. The goal is to reduce the distance between your "near clipping plane" and the "far clippling plane" which is automatically determined by the surfaces that are farthest from the camera. If you can't make the z-fighting go away by adjusting the Clip Sufaces Within setting then you will need to remove surfaces that are far away from the camera. By keeping the distance between the closest and farthest surfaces down to a reasonable value, you should be able to solve most z-fighting problems. Another way you can solve the problem is by making sure you don't have surfaces that are close to each other. Making your roof or wall layers thicker can often do this.

[Dermot Dempsey]

"I found a setting the the Camera defaults that was set to 300" and I tried 100" and then 48" but it had no effect ???"

You probably adjusted the "Clip Plane Indicator Length". This setting only affects the plan view display of cross section/elevation cameras. Please read my previous post to get information about how to solve your z-fighting issue.

[lbuttery]

"Clip Surfaces Within"


Dermot:

I set it to 8' and it works !!!

I didn't try lower settings as this is a "campus" and the distances are large


In the pic I posted earlier, each of the buildings is a .3ds symbol so the roof thickness etc shouldn't be coming into play - should it ???

thanks

I think this problem is solved

Lew