Paint gloss levels (30%, 50%, 70%...)...What roughness in KS?

[DriesV]

Hi,

Paints are typically available in three flavors:
Matt 30% shine, Satin 70% shine, Gloss 85% shine.

I want to accurately match my KeyShot paints to real-life gloss levels.

It is clear to me that a 100% shine paint should have a roughness of 0.
But what rougness should a 70% or 30% shine paint have?

It seems that the slider for roughness maxes out at a value of 0.5 (although it can be set higher manually). With what gloss level does this value correspond?

greetings,
Dries

[KeyShot]

Hi Dries,

The relationship with gloss is quite complex and non-linear. I assume you are referring to a 60 degree gloss.
The corresponding roughness values are approximately. 30% = 0.07, 70% = 0.03, 85% = 0.02.
Feel free to email info@luxion.com if you want to discuss this in more detail.

-- Henrik

[DriesV]

Hi Henrik,

I am indeed referring to 60 deg gloss.
Thanks for your update on the roughness values for mentionned gloss levels.

Is it possible to give the approximate roughness for gloss levels of paint ranging from 0% to 100%, with increments of 10%?
I would like to see what the relationship is between both units.

Dries

[DriesV]

Does it go something like this?

f(x) = -0.048 * ln(x) + 0.0126
(Viable in gloss range 10% to 90%)

Where f(x) is roughness (KS values) and x is gloss (in %).

[DriesV]

I made these paint material sample overviews based on my logarithmic function that I posted earlier.
The first image has the painted balls in a neutral studio EV, in the second image they're placed in an interior EV.

Highlighted in orange are the actual KeyShot roughness values.

I've compared these overviews to a few physical paint samples that I have laying around and that I know the gloss level of. They seem to be pretty accurate represenations.

Note:
The Black cubes were added to aid in evaluating the reflection of objects in close proximity to the painted balls.

greetings,
Dries

[PhilippeV8]

neat case study =)

[m2tts]

Thanks, I just saved that image for future reference.

[PhilippeV8]

KS better add this in the manual for KS4 *hint*

[guest84672]

Very good. Thanks for posting.