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Comprehensive Guide

Vol.1 - The Theory of Physically based Rendering - click here

Vol.2 - Practical Guidelines for PBR Texturing - click here

 

General

UDK Physically Based Lighting - click here

Free Engines Supporting Physically Based Lighting - click here

TGA Physically Based Lighting CGFX Shader for Maya Viewport - click here

 

Science & Theory

Water Drops & Wet Surfaces PBR- click here

Sebastien Lagarde’s Adopting a physically based shading model

Feeding a Physically Based Lighting Mode - click here

SIGGRAPH 2014 Course: Physically Based Shading in Theory and Practice - click here

John Hable’s excellent blog post: Everything Is Shiny

John Hable’s even better blog post: Everything Has Fresnel

The SIGGRAPH 2010 course on PBR

Always worth mentioning: The Importance of Being Linear

Slideshow of Real Shading in Unreal Engine 4

Mike Seymour’s Monsters University: rendering physically based monsters

Physically Based Rendering - From Theory to Implementation

 

 

Practice

Sébastien Lagarde’s summary of Rendering Remember Me

 

 

Discussions

Polycount discussion on PBR -click here

Polycount PBR Texturing Process Q&A-click here

Reddit Star Citizen PBR Discussion-click here

 

 

 

FAQ

I don’t know how to use a PBR system, will I need to re-learn how to create art content?

In most cases, no. If you have experience with previous generation shaders which use dynamic per-pixel lighting you already possess much of the knowledge necessary to create content for a PBR system. Terminology tends to be one of the biggest stumbling blocks for artists, so I have written a section on various terms and translations below. Most of the concepts here are simple and easy to pick up.

 

If your experience lies mostly with hand painted/mobile work, learning the new techniques and workflows outlined here may be more of a challenge. However, likely not more difficult than picking up a traditional normal map based workflow.

 

If I use a PBR shader does that mean my artwork is physically accurate?

Not necessarily; simply using a PBR shader does not make your artwork physically accurate. A PBR system is a combination of physically accurate lighting, shading, and properly calibrated art content. The deciding factor on whether or not it looks physically accurate is the texture work.

 

Do I need to use a metalness map for it to be PBR?

No, a metalness map is just one method of determining reflectivity and is generally not more or less physically accurate than using a specular color/intensity map.

 

Do I need to use index of refraction (IOR) for it to be PBR?

No, similar to the metalness map input, IOR is simply an alternate method to define reflectivity.

 

Is specular no longer a thing?

Not quite. Specular reflection intensity, or reflectivity is still a very important parameter in PBR systems. You may not have a map to directly set reflectivity (e.g. with a metalness workflow) but it is still required in a PBR system.



 

Do gloss maps replace specular maps?

No, gloss or roughness maps define the microsurfaceof the material (how rough or smooth it is), and do not replace a specular intensity map. However, if you’re not used to working with gloss maps, it may be somewhat of an adjustment to put certain detail in the gloss map that you would otherwise add to the specular map. Generally spec maps (in the non-metalness workflow) are quite flat in comparison to its predecessor while gloss/roughness maps remain more or less the same; all the microsurface details are located here. Even those that would be too small for the normal map. (depending on the engine).

 

Can a PBR system be used to create stylized art?

Yes, absolutely. If your goal is to create a fantastical, stylized world, having accurate material definition is still very important. Even if you’re creating a unicorn that farts rainbows, you still generally want that unicorn to obey the physics of light and matter. A great example of this is Pixar’s work, which is very stylized, yet often on the cutting edge of material accuracy.

Here is a great article about PBR in Monsters University: fxguide feature on Monsters University

Here is another example created by our resident stevston89 of polycount: PBR Stylized Dagger

 

What is all this talk about sRGB, gamma, and linear? And why is it important?

sRGB, gamma, and linear are colour spaces used when defining a certain colour. A simpler way to think about it is RGB vs CMYK. sRGB stands for standard RGB colour space. This is basically how light/information is displayed.

 

sRGBis for all intensive purposes, synonymous with gamma (gamma corrected). It is of an exponential graph. 0 - 255. As an fyi, the neutral gray/mid point of a gamma colour space is 187, not 127/128.

Linearis, as it sounds, a linear graphic. 0 - 1

 

Does the old workflow of baking in the AO/cavity into your diffuse and spec still apply?(source)

[AO]No. In the PBR workflow it does not apply. (Check with your respective engine/shader for more details) I leave it to the infamous Earthquake of Marmoset to elaborate.

[Cavity]It can still be applied to the albedo and spec maps. (Check with your respective engine/shader for more details) Engines like TB2 offer the ability to input an occlusion and cavity map with sliders to adjust its influence on diffuse/spec.

 

Large scale AO really should notbe bakedinto specular(or the metallic materials of an albedo map when using the metalness workflow), or diffuse, this just does not make much sense physically. As mentioned above, when you do that, your AO is occluding direct light sources, which is very much the incorrect thing to do. Just think about it for a second, if you have the inside of a helmet, naturally your baked ao map would get a lot darker there right? Now, put a light source directly inside that helmet, what happens in real life?

 

If that content is baked into your textures, you can never light that area correctly in a game.

 

Is one workflow or route better than the other?

Not really, it’s just boils down to which you personally get better results from, are more comfortable with, which engine you are using, and if you are texturing in an office, which method they use.

 

Will artists need to capture photographic reference with a polarized camera system for every material they wish to create?

No, generally you will be provided with reference for common materials by your studio. Alternatively, you can find known values from various 3rd party sources, like Quixel’s Megascans service. Creating your own scan data is a very technical and time consuming process, and in most cases not necessary. However there is a quick tutorial located here.

 

Is there a way to grab albedo/spec, etc values from real life?

There is! But it requires some equipment and knowledge of colour space as well as how to use a camera. On top of that it requires knowledge of the Macbeth chart and other various “tools” to get an accurate reading. Polycount’s almighty_gir has made a quick tutorial on this.

 

Caution: If you have no clue what you are doing, you could potentially be pulling inaccurate values. Consult the tutorial and read through the posts for a better understanding.

 

Where is texturing headed? Is it going to be procedural from now on?

There’s no definitive answer for this. What I do know is that more procedural tools are becoming more available. They are a blessing and a little bit of a curse I think. Blessing because it speeds up production and accuracy but for those who are not competent on texturing and rely on these programs may not see their skill level increase and if their studio does not have said tool, well they’re on their own. Some procedural-oriented tools off the top of my head include Substance Designer and DDO. Still if one has time, it’d be of their benefit to learn such programs and add them to their arsenal.

 

Is there a central database for material values for albedo, spec, roughness, etc?

There is and there isn’t. There is from those that are publically shared and there isn’t from the studios whom use their values specific to their engines. Regardless, please do take care when using values and don’t pigeonhole yourself into thinking that a value is the only value for that material.

 

Any tips for making my work look good?

Ensure that you have accurate albedo, spec, and roughness values. Once you do and a decent texture job has been done, your object will look great in any lighting condition. Don’t adjust values for a specific lighting environment as it may not look as well in other settings, etc.

 

How do I make sure I have the “exact” value needed for a material?

There is no exact value for any given material as in the real world, many factors influence the physical values of that item. Long story short, just utilize some base values found online as a starting point and adjust it in small increments until it looks like the material you’re attempting to represent. It becomes easier with more practice and looking up values will be needed less.

 

Is there a way to get better at PBR/PBT?

Yes. There are multiple ways. Some include: practice - you’ll get no where and won’t get any better without practice. Tutorials and looking at other artists’ work (assuming their work is accurate) will help train your eye into identifying what looks accurate. Another way is to learn more about science and physics and the nature of light/materials and their interaction with each other and the world around us. You kind of have to step into the realm of a technical artist almost...just a smidge.

 

I’m new to PBR but it looks like this method of texturing is a lot more troublesome than before?

Not true in my opinion. It may look this way because this is new to you but once you’ve gotten used to it or know of the workflow, it’s actually simpler in a sense, and quicker. You don’t have to repeat diffuse details in all other maps, ensure gloss looks interesting VS spec and diffuse, etc. As well, more procedural based/material layering software has come into the market that aid in next-gen texturing.

 

 

 

Glossary & Terms

AO - Ambient Occlusion

CE3 -CryENGINE 3

PBR -Physically Based Rendering

PBT -Physically Based Texturing

UDK -Unreal development Kit

UE4 - Unreal Engine 4

* - Denotes that the accuracy of the information is in review.

TL;DR - Too Late; Didn’t Read

TB2 - Marmoset Toolbag 2

F0- base reflectance. It simply refers to how much light a surface reflects when looking directly at it (source)

- fresnel zero (when fresnel has zero effect; what colour is the object when fresnel has no effect) (source)

F- Fresnel.How much light is reflected at a grazing/glancing angle (source)

- named after French engineer and physicist Augustin-Jean Fresnel

 

 

 

Tools & Programs

Tools & Plugins

Materialing Alpha- Free Photoshop PBR Material Painting - developed by Andrew “d1ver” Maximov. Plugin for Photoshop.

 

 


Date: 2015-12-24; view: 1255


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