Scene scale startegy

[pciccone]

Hi.
I did a lot of testing about scene scale issues and I need some suggestions. We know that a Lux Unit (LU) is equal to 1m. A DAZ Studio unit (SU) is 1cm. When exporting a scene to Lux I divide each unit by 100.
Unfortunately this seems to introduce some precision issues that create artifacts in the scene. If I don't scale the units the resulting image looks better but then I have all kind of issues related to physical size.
Volumes are wrong, light is affected etc.
Is there a way of setting the unit of measure in Lux at the beginning of the scene to an arbitrary amount, so that I can specify that all the number are actually 1/100 of a meter? Or maybe there is a better approach?

Thanks in advance.

[jeanphi]

Hi,

Unfortunately not yet. However this is a known issue and should be dealt with sooner or later.

Jeanphi

[pciccone]

Thank you Jeanphi.

[pciccone]

Jeanphi.
Would it make sense to do something like this:

AttributeBegin
# Scale from SU to LU
Scale 0.01 0.01 0.01
NamedMaterial "mymat"

Shape "trianglemesh" "point P" [
...
]
AttributeEnd

And output the vertex list in Studio Units?

Thanks.

[Lord Crc]

Yes that should work well in most, if not all, cases. If you have other transformations you need to take care of the ordering though. This should avoid precision issues due to limited number of decimals used when outputting the floats.

[pciccone]

Thank you , unfortunately it doesn't solve the issue. I'll post more later, after the renders end.

[Lord Crc]

I forgot that lights may not like this, so stick with the old way for them. Btw what's the current status on this jeanphi?

[pciccone]

Good to know, yes, lights are scaled by division.

Thanks.

[jeanphi]

Hi,

This should work for mesh lights too since LuxRender applies the transform to the mesh coordinates when loading the mesh and no tranforms are done afterward.
However it won't work correctly for other primitives (spheres, ...). If you use instances, you also need to be careful to apply the transform only once (on the base object or the instance).

Jeanphi

[pciccone]

Good to know, thanks.