Preset BMW339 Carpaint in luxrender 0.9dev

[Bao2]

I am playing with carpaint material and I think I found there is a problem perhaps in luxrender, perhaps in luxblend25, I don't know.

In the pdf the developpers (jeanphi I suppose) followed to create the carpaint material, there is a table where you can find these values for BMW 339 carpaint:

Absorption 000000 (not in the pdf I set it to 000000 as jeanphi suggested)
Diffuse .012 .015 .016
Spec1 .062 .076 .08
Spec2 .11 .12 .12
Spec3 .0083 .015 .016
M1 .39
M2 .17
M3 .87
R1 .92
R2 .013
R3 .9

Well if you render with the above carpaint material you get a different result than if you render choosing the BMW339 preset.
The preset gives a much more carpaint look. The values from the pdf gives much more matte material.

Is possible to know what values is the preset using ?

[jeanphi]

Hi,

The preset is using those values but without applies reverse gamma correction, while user settings are gamma corrected by the exporter. So either disable reverse gamma correction or manually correct the values so that the reverse gamma correction will give the paper values.

Jeanphi

[J the Ninja]

Luxblend25 does not do reverse-gamme correction, Blender 2.5 stores colors in linear space to begin with, and the RGB mode of the color picker manipulates the stored linear RGB value directly. The color-picker gamma corrects hex-codes as they are input, and that's the extent of it.

EDIT: My C++ skills are practically nil, but looking at materials/carpaint.h setting name="bmw339" seems to load:

Kd: .012 .015 .016
Ks1: .062 .076 .08
Ks2: .11 .12 .12
Ks3: .0083 .015 .016
M1: .39
M2: .17
M3: .013
R1: .92
R2: .87
R3: .9

EDIT 2: Bao2, are you sure you didn't misread the table and punch an R value in for M or something? Punching in the values for the paper looks exactly like the preset here.

[jeanphi]

Hi,

Indeed, and LuxRender preset matches the paper while Bao2 data doesn't

Jeanphi

[Bao2]

Yes, I swapped M3 and R2 values.
Thanks for the quick replies.