PBR Texture....ALBEDO Photosource

Dave Jr

Hi,

I'm currently practicing PBR and learning an efficient workflow of using photo-sourced images for PBR materials. Apologies for my noobness; I'm reading over a few different written sources.

Am I right in thinking that ANY photograph I use must be corrected by;

using a linear SRGB file type
Equalising the image
removing any lighting information/cavity information within the image
then calibrating via exposure and colour correction to match the Macbeth chart?

It seems an extremely long workflow and how would I rectify this with images I haven't taken myself? I wouldn't have a Macbeth chart in the image provided to match up with actual RGB values.... Would I just match it to the values posted on marmoset for albedo?

Cheers!

EarthQuake

Linear space and sRGB (gamma space) are two different things. Generally for an albedo map you would use sRGB, but most engines have options to do either. I know in TB2 and UE4 you can choose either linear or sRGB. sRGB is generally used for maps that you create by "look" like albedo maps, while linear space is generally used for mats that represent math or precentages, like normal maps, metalness maps, and gloss/roughness maps.

I'm not sure what you mean by equalizing the image, but removing lighting information is an important step.

Ideally the texture reference would have been taken with a color chart yes, if you don't have that, you'll have to eye-ball it, and if you can find measured values for a similar material type you can compare it to make sure you're within a reasonable tolerance.

Its important to note that albedo values will vary a great deal, you'll find many variations of red plastic in the world for instance, so there usually isn't a "correct" albedo. So you need to use your better judgement, combined with research and observation to come to a reasonable value.

Dave Jr

Wow,

thanks for the quick response Earthquake. So its literally a matter of being accurate when plausible (i.e. when taking the images yourself) but when using sources provided matching them as close as possible to similar objects i.e. like the library marmoset has kindly offered for a few objects.

By equalising I meant this;

http://tolas.wordpress.com/2009/05/26/tutorial-how-to-equalize-textures-in-photoshop/

In regard to removing any AO/light info is there a quick way of achieving this or is it manually just blending over with the clone tool etc to clean up selected areas.

EarthQuake

Yeah, when you can take the reference material yourself, the goal should be accuracy. But its not going to be feasible to take all of your own reference. Certain services like Quixel's Megascans will help here as they provide calibrated textures, but its not out yet unfortunately. If you can't find calibrated content, you just need to use your better judgement really.

Re: equalize, so you just mean remove lighting and shadow information, ok that makes sense, so this isn't really two steps, just one step. There are a variety of ways to do this, using the high pass filter or a variety of different methods, I would just search for "remove lighting from texture" you should find some tutorials.

When you take reference photos yourself generally you should take them on an overcast day to avoid heavy directional lighting, and you can also look into cross-polarization to remove specular lighting as well.

Dave Jr

Awesome thank you

Chimp

In addition to EarthQuake's good advice, you should check out Bitmap2Material by Allegorithmic - it's a time saver for sure

iniside

For removing dark spots/dark shadows you might try, if you are using photoshop.
1. Select color range.
2. Then, Content-Aware fill. Unless you have really big shadows it tends to work quite nice.

As for photo textures I'm of two ways here.
If material is very rough (like concrete, rough wood, brick wall, rock, you got the idea), then best you can do is eyeball it and just check how does it look in your target engine. Once you get some experience you won't need to check often in engine how does your material look.
If your material is reflective (like metals, polished wood, plastic), then taking photos for your color is pointless, and not really required.

I mean if you are not feeling like creating more or less complex pattern for polished wood, then you can grab something of cgtextures or other source.
In anycase the defining factor of look in that case will be roughness of material and normal map.

Finding something like roughness measurements for every material is simply impossible, since every engine might take different valus (or don't have roughness at all, compare CE3 Gloss 0-255 to UE4 Roughness 0-1).
And aside from that you don't make roughness maps with uniform color. The point of roughness is to have variety of roughness over surface to make it less uniform. Unless you really want it to be uniform.

Your best bet is to simply eye ball until you think it looks like the material you want to simulate.

almighty_gir

there's also this:

http://www.polycount.com/forum/showthread.php?t=136486

Xoliul

Keep in mind that after removing lighting, for non-metals you should stick to albedo ranges between 30/255 and 240/255.

Dave Jr

Thank you guys for so much feedback I am definitely enlightened and am sure many others will find this thread useful in the future.

marks

Xoliul wrote: »

Keep in mind that after removing lighting, for non-metals you should stick to albedo ranges between 30/255 and 240/255.

sRGB yeah?

youssouf124

hello, for the albedo correction the most simple way is to use a color correction tool like this
https://colortarget.wordpress.com/

I think there is a demo on their site, you can try

youssouf124

if you work from non raw source, you can also use this one
https://colortarget.wordpress.com/