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Author Topic: aliasing artifacts with proximitySensor  (Read 3383 times)
frederik
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« on: September 23, 2010, 11:29:02 am »

Hello!

I'm creating a fairly big scene with several geological strata (indexedFaceSets) stacked on top of each other. In some areas they are intersecting and very close to one another (almost coplanar).

After adding a ProximitySensor to create a HUD the aliasing artifacts (polygon tearing?) appeared. (See picture.) Scaling down the objects (scale/100) in order to downsize the ProximitySensor reduced the artifacts but didn't stop them completely. They appear in certain angles only.

I read about something seemingly similar in Brutzman, 2007, 3D graphics for Web authors (p. 110), so I changed avatarSize and visibilityLimit, which made it worse. I use DirectionalLighting and HardShadowMode.

It seems to work fine in Xj3D, but I really prefer InstantPlayer.

I am quite new to whole X3D thing, and I hope I found the right place to post my question.

Thanks!
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yjung
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« Reply #1 on: September 24, 2010, 10:20:45 am »

Hi Frederik,

Quote
I'm creating a fairly big scene with several geological strata (indexedFaceSets) stacked on top of each other. In some areas they are intersecting and very close to one another (almost coplanar).
[...]
I read about something seemingly similar in Brutzman, 2007, 3D graphics for Web authors (p. 110), so I changed avatarSize and visibilityLimit, which made it worse. I use DirectionalLighting and HardShadowMode.

funny, some years ago, I did almost the same thing with InstantPlayer and had to deal with the same problems. Instead of the ProximitySensor I used the Viewspace (however, without tuning it results in the same z-problems), where the GUI is based on a UITexture (BTW, if you're interested, in this thread you'll find some more information: http://forum.instantreality.org/index.php?topic=614.0).

The hints mentioned in Don's book are ok with standard X3D, but alternatively you mostly can alleviate these z-fighting issues by either setting the zRatio in the ContextSetup (which is used to automatically calculate the near and far clipping plane - preferably this value should be around 5000) or by directly setting the zNear and zFar fields of the Viewpoint node (which deactivates the automatic calculation, which in case of HUDs sometimes fails). You can also find some more information on this here: http://forum.instantreality.org/index.php?topic=183.msg674#msg674.

Hope this helps
Yvonne
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frederik
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« Reply #2 on: September 27, 2010, 09:33:56 am »

Thanks so much, Yvonne!

It looks pretty now! Smiley
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brutzman
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« Reply #3 on: July 01, 2012, 09:04:34 pm »

Good to read that things began working better.  Am concerned however that you had to use a specialty technique not available in all X3D players.

Wondering if changes to X3D specification need to be considered and proposed?
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