Many Pbr Questions
polycounter lvl 6
We should use real world albedo and specular values in textures.I really don't understand, even if i use something which almost look leather or almost look gold.It should do the job.We are making characters,environment, props etc for games, not for a science project.Where everything need to be dead on.
If i don't have these real world data regarding albedo and specular then what should i do.
Is it necessary to use albedo from a real world data?What if i just use an approximate colour.
On marmoset website it says satin albedo is 0.43 in linear space and 0.69 in srgb.How do i find which linear and srgb value correspond to a particular colour in photoshop or in any other software.There is no option to put a floating value of .43 or .69 in photoshop and get the colour information from it.
specular colour at F0 should be taken from real world.So that it behave physically correct.Where is all this data regarding reflectance at F0 of everything.
I Just don't understand why everything needs to be so precise.For example if i use satin colour as 0.49 or something which is closer to satin instead of 0.43.It will be still be almost satin.The end user that is the gamers are not going to throw there Ps4 or Xbox out of the window just because the value is not spot on.Some people may argue that its almost satin but not exactly satin.Well i don't think the difference would be like night and day, even if you use approximate colour.
How light interact in physically based rendering that show a huge improvement.
But using these dead on value is something i having a really hard time. Going to sleep.I hope i don't have nightmare regarding PBR :poly142: :poly142:
If i don't have these real world data regarding albedo and specular then what should i do.
Is it necessary to use albedo from a real world data?What if i just use an approximate colour.
On marmoset website it says satin albedo is 0.43 in linear space and 0.69 in srgb.How do i find which linear and srgb value correspond to a particular colour in photoshop or in any other software.There is no option to put a floating value of .43 or .69 in photoshop and get the colour information from it.
specular colour at F0 should be taken from real world.So that it behave physically correct.Where is all this data regarding reflectance at F0 of everything.
I Just don't understand why everything needs to be so precise.For example if i use satin colour as 0.49 or something which is closer to satin instead of 0.43.It will be still be almost satin.The end user that is the gamers are not going to throw there Ps4 or Xbox out of the window just because the value is not spot on.Some people may argue that its almost satin but not exactly satin.Well i don't think the difference would be like night and day, even if you use approximate colour.
How light interact in physically based rendering that show a huge improvement.
But using these dead on value is something i having a really hard time. Going to sleep.I hope i don't have nightmare regarding PBR :poly142: :poly142:
Replies
the more you know about the scientific properties of a material the more "knowns" you have when you're making observations. if you know what color a piece of steel actually reflects in real life then it's one less thing you have to derive from looking at a picture. if you don't know, it isn't the end of the world, but you have to think through more things to end up with an accurate result.
in other words, end result is all that matters but using lookup charts is a way of leveraging the observation (or measurement) that others have already done.
Just one last thing on marmoset website it says satin albedo is 0.43 in linear space and 0.69 in srgb. How do you find which colour correspond to these value in photoshop.
To go from 0-1 -> 0-255
result = x * 255
To go from 0-255 -> 0-1
result = x * (1/255) = x * 0.00392
To go from Gamma -> Linear
result = x^2.2
To go from Linear -> Gamma
result = x^(1/2.2) = x^0.4545
The gamma 2.2 is true in most cases, may differ for some cases.
Linear to Gamma
0.43^(1/2.2) = 0.45^0.4545 = 0.6956 (actually 0.6814 if you use more decimals)
Your 0.43/0.69 you asked for in 0-255 space would be:
0.43 * 255 = 110 (linear space)
0.69 * 255 = 176 (gamma space)
I was like shit, there's a lot of material values that you just can't find handily on the net.
But then i just started eye balling the values, and making sure i work proceduraly so my team mates or myself could change the values later on if need be.
Echoing what Amsterdam said, it defiantly makes it a lot easier having the values at hand for communicating materials better between team members. No one's going to call you out if its not 100% accurate though.
Try not to look at this as sucking the fun out of your artwork, it just makes it so you need to make far less tweaking work and the end result can be used for any lighting situation.
Those equations returns a single value.But photoshop understand in terms of RGB,hex,HSB. So how would you find a color with just a single value.
Link?
Here is the sebastien Lagrade blog.See "diffuse color" section point 2 "taking physical albedo value" http://seblagarde.wordpress.com/2011/08/17/feeding-a-physical-based-lighting-mode/
on Marmoset web site look in albedo section http://www.marmoset.co/toolbag/learn/pbr-practice
I suppose this is the picture you got those values from? I was trying to ctr+f through the page for "satin" and was coming up short
Yes that's the picture which i was talking about.But still i have no idea how to use those linear value in term of colour.Where i have to put those values to find the corresponding colour.
Thank you for helping me out.:)
In terms of what the numbers mean in that image, kodde is correct luminance or brightness. You don't actually have to do any math to figure out what numbers to use, just look at the brightness value in photoshop's color picker.
Its also important to note that these are simply examples of some specific materials. This means that you don't have to stick to those values exactly, for instance rocks come in all different colors.
On a serious note though. Don't think about PBR as a harsh set of values, the purpose of charts is to layout a basic guideline for values so when you are authoring materials you have some idea of what your values might look like.
Physically based rendering is certainly a more scientific approach to rendering but the purpose of it is to speed up production, part of that requires the artist to think a little bit more about materials in a real world sense.
If you have not already seen the PBR Encyclopedia I would recommend checking that out HERE It has a load of information and quite a few links to tutorials and breakdowns of how some PBR pieces got their material definition.