Rendering flaw on 6630, 6681 with SkinnedMeshes

[swylieto]

We have encountered some problems with the SkinnedMesh implementation on the Nokia 6630, 6681.

The effect is a 'water bag' where the geometry of the model will actually fluctuate and ripple during animation.

This only occurs with SkinnedMesh objects.

It appears to be a series of rounding errors that vary over frames. If the model is not animated the effect is not visible. The problem only occurs when the model is in animation.

Any help would be appreciated.

[mkochano]

I have exactly the same problem with SkinnedMesh on nokia 6630 i'm fighting with it almost 4 days and i think i will give up soon...i tried almost anything in 3dmax and and still didnt get much - it works on Motorolas, SonyEricssons, Siemenses i think even on my watch... but not on nokia 6630 - vertices are snapping around and event making mesh bigger doesnt change anything...it's sad that someone who tested the immplementation didnt spotted this one..or maybe it is made for purpose? I have no idea - any help will be appreciated

cheers...

[mkochano]

Hi again above error has nothing to do with two nokia bugs that i found somewhere:
"* Duplicated SkinnedMesh nodes do not animate. The best workaround for most cases is to load the mesh multiple times, then copy the Appearance and VertexArray objects from the first instance to avoid multiple copies of large data elements. Fixed in the wk15 2005 release.

* SkinnedMesh vertices not attached to any bones may move erroneously. This can be avoided by attaching all vertices to at least one bone, which usually is the case with skinned models. Fixed in the wk15 2005 release."

Its something different.

Cheers

[taarnio]

This is very likely caused by a skinning precision bug we found a year ago. The fix may have made its way to some of the very recent products, but the 6630 and 6681 are certain to have it. Quoting our internal M3G bug database:

* * * * *
Arithmetic precision in skinning is too low, resulting in blocky images in certain cases. This occurs when the scaling components of bone matrices are several orders of magnitude smaller than their translation components, which may be the case with very finely detailed meshes having thousands of vertices. Found 2005-09-15, fixed 2005-09-16, released wk39 2005.

Workaround: Simplify the mesh and reduce the precision of vertex coordinates from 16 bits to, for example, 12 effective bits. As a secondary measure, try dividing the mesh into two or more parts, such that the tail, wings, or other long appendages are put into separate SkinnedMeshes.
* * * * *

I hope you can find a suitable workaround.

Good luck,
Tomi
-------------------
Tomi Aarnio
Spec Lead, JSR-184/297
Nokia Research Center

[mkochano]

Thanks for reply and some advices, unfortunetelly i didn't found any of them working for me so i just left the game as it was...cheers

[jheanley]

Hi,

Just wondered how one is supposed to reduce the accuracy from 16 bits. Our max modellers say they dont know of any functions to do this within max.

cheers

Jules

[taarnio]

You might have a setting in your Max exporter to export the coordinates at 8 bits per vertex rather than 16. If that doesn't help or is not possible, then you could try splitting the SkinnedMesh into multiple parts.

--tomi