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The Comprehensive PBR Guide Vol.2
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The Comprehensive PBR Guide vol. 2 Light and Matter : Practical guidelines for creating PBR textures Cover by Gaëtan Lassagne, written by Wes McDermott
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The Comprehensive PBR GuideThe Comprehensive PBR Guide
by Allegorithmic - vol. 2by Allegorithmic - vol. 2
Light and Matter : Practical guidelines for creating PBR texturesLight and Matter : Practical guidelines for creating PBR textures
Cover by Gaëtan Lassagne, written by Wes McDermottCover by Gaëtan Lassagne, written by Wes McDermott
vol. 2 - Practical guidelines for creating PBR texturesvol. 2 - Practical guidelines for creating PBR textures
Page 1Page 1
Table of ContentsTable of Contents
• What is PBR? - 3• What is PBR? - 3
What are the benefits? - 3What are the benefits? - 3
What does it mean for the artist? - 3What does it mean for the artist? - 3
• Metal/Roughness Workflow- 3• Metal/Roughness Workflow- 3
Dielectric F0 - 5Dielectric F0 - 5
Base Color - 5Base Color - 5
Creation Guidelines - 6Creation Guidelines - 6
Metallic - 7Metallic - 7
Creation Guidelines - 8Creation Guidelines - 8
Raw Metal - 8Raw Metal - 8
Corroded or dielectricl layer - 9Corroded or dielectricl layer - 9
Roughness - 10Roughness - 10
Creation Guidelines - 11Creation Guidelines - 11
Resolution and Texel Density - 11Resolution and Texel Density - 11
Creation Guidelines - 12Creation Guidelines - 12
Pros and Cons of Metal/Roughness Workflow - 12Pros and Cons of Metal/Roughness Workflow - 12
• Specular/Glossiness Workflow- 13• Specular/Glossiness Workflow- 13
Diffuse - 13Diffuse - 13
Creation Guidelines - 13Creation Guidelines - 13
Specular - 14Specular - 14
Creation Guidelines - 14Creation Guidelines - 14
Raw Metal - 14Raw Metal - 14
DielecDielec
tric - tric -
1515
Glossiness - 16Glossiness - 16
Creation Guidelines - 16Creation Guidelines - 16
Resolution and Texel Density - 16Resolution and Texel Density - 16
Creation Guidelines - 17Creation Guidelines - 17
Pros and Cons of Specular/Glossiness Workflow - 17Pros and Cons of Specular/Glossiness Workflow - 17
• Maps common to both workflows - 18• Maps common to both workflows - 18
Ambient Ambient
Occlusion Occlusion
- -
1818
Creating Ambient Occlusion - 18Creating Ambient Occlusion - 18
Height - 19Height - 19
Creating Height - 19Creating Height - 19
Normal - 21Normal - 21
Creating Normal - 21Creating Normal - 21
• Substance PBR Utilities - 22• Substance PBR Utilities - 22
Materials - 22Materials - 22
Bitmap2Material3 - 22Bitmap2Material3 - 22
PBR Base Material - 22PBR Base Material - 22
PBR Substance Materials - 23PBR Substance Materials - 23
Reflectance Values - 23Reflectance Values - 23
Dielectric F0 - 23Dielectric F0 - 23
Metal Reflectance - 23Metal Reflectance - 23
Correction - 24Correction - 24
PBR Metal/Roughness Validate - 24PBR Metal/Roughness Validate - 24
PBR Safe Color - 25PBR Safe Color - 25
Conversion - 25Conversion - 25
Metal/rough to Spec/Gloss - 25Metal/rough to Spec/Gloss - 25
• Appendix - Charts - 26• Appendix - Charts - 26
Is the surface metal? - 26Is the surface metal? - 26
Reflectance Values - 27Reflectance Values - 27
Correct/Incorrect Comparisons - 28Correct/Incorrect Comparisons - 28
Technical edit by: Nicolas Wirrmann and Jeremie NoguerTechnical edit by: Nicolas Wirrmann and Jeremie Noguer
Copy edit by: Alexandre BagardCopy edit by: Alexandre Bagard
vol.2 - Practical guidelines for creating PBR texturesvol.2 - Practical guidelines for creating PBR textures
Page Page
22
Light and MatterLight and Matter
Practical guidelines for creating PBR texturesPractical guidelines for creating PBR textures
Physically Based Rendering (PBR) can be thought of as more of a methodology than a hard standard. There arePhysically Based Rendering (PBR) can be thought of as more of a methodology than a hard standard. There are
specific principles and guidelines, but not a true standard and thus there can be different implementations. Thesespecific principles and guidelines, but not a true standard and thus there can be different implementations. These
differences can typically be found in the map types used i.e. the workflow, the BRDF and how data values fordifferences can typically be found in the map types used i.e. the workflow, the BRDF and how data values for
roughneroughne
ss/gloss/glo
ssinesssines
s s
could be could be
remapremap
ped for ped for
customcustom
ized implementatized implementat
ions. There ions. There
are are
even implementateven implementat
ions thations that
change the map names, but the underlying usage is still the same.change the map names, but the underlying usage is still the same.
In this guide we will discuss the two most common workflows, which are metal/roughness and specular/glossiness asIn this guide we will discuss the two most common workflows, which are metal/roughness and specular/glossiness as
shown in figure 01. The Substance toolset for authoring PBR maps, which is comprised of Substance Designer,shown in figure 01. The Substance toolset for authoring PBR maps, which is comprised of Substance Designer,
SubstaSubsta
nce Painter nce Painter
and Bitmap2Maand Bitmap2Ma
terial 3, terial 3,
support both support both
workflworkfl
ows. The ows. The
SubstaSubsta
nce PBR nce PBR
shadeshade
rs rs
for metal/roughnefor metal/roughne
ssss
and specular/glossiness use GGX BRDF and do not utilize any value remapping for roughness/glossiness. However, ifand specular/glossiness use GGX BRDF and do not utilize any value remapping for roughness/glossiness. However, if
any custom remapping is needed, this can easily be implemented in the Substance material. Furthermore, customany custom remapping is needed, this can easily be implemented in the Substance material. Furthermore, custom
shaders are supported in the Substance toolset, which means you can adapt Substance to any customized pipeline.shaders are supported in the Substance toolset, which means you can adapt Substance to any customized pipeline.
It’s important to state that while both workflows each have pros and cons in their implementation, one workflow is notIt’s important to state that while both workflows each have pros and cons in their implementation, one workflow is not
particularly better than the other. What is truly important is that you understand the core principles behind PBR. It’sparticularly better than the other. What is truly important is that you understand the core principles behind PBR. It’s
the concepts and guidelines that make the PBR maps you author accurate and not the workflow itself. The workflowsthe concepts and guidelines that make the PBR maps you author accurate and not the workflow itself. The workflows
represent the same data, but they implement the data in different ways.represent the same data, but they implement the data in different ways.
In Volume One of "The Comprehensive PBR Guide," we defined PBR from a technical and theoretical standpoint. InIn Volume One of "The Comprehensive PBR Guide," we defined PBR from a technical and theoretical standpoint. In
this 2nd Volume, we will discuss the practical application of authoring PBR textures and provide a set of guidelines thatthis 2nd Volume, we will discuss the practical application of authoring PBR textures and provide a set of guidelines that
are based on the foundations established in Volume One. We will begin by redefining PBR from an artistic perspective.are based on the foundations established in Volume One. We will begin by redefining PBR from an artistic perspective.
From there, we will discuss the metal/roughness workflow to address the principles and guidelines. We will then followFrom there, we will discuss the metal/roughness workflow to address the principles and guidelines. We will then follow
up with the specular/glossiness workflow and only detail the differences in the authoring methods. Therefore, it is bestup with the specular/glossiness workflow and only detail the differences in the authoring methods. Therefore, it is best
to read through both workflows to get a full idea of the overall guidelines for authoring PBR textures.to read through both workflows to get a full idea of the overall guidelines for authoring PBR textures.
Figure 01Figure 01
vol. 2 - Practical guidelines for creating PBR texturesvol. 2 - Practical guidelines for creating PBR textures
Page 3Page 3
We as artists need to think differently about the maps that describe theWe as artists need to think differently about the maps that describe the
attributes of a surface. There are new map types with rules and guidelinesattributes of a surface. There are new map types with rules and guidelines
to follow.to follow.
Physically Based Rendering (PBR) is a method of shading and rendering that provides a more accurate representationPhysically Based Rendering (PBR) is a method of shading and rendering that provides a more accurate representation
of how light interacts with surfaces. It can be referred to as Physically Based Rendering (PBR) or Physically Basedof how light interacts with surfaces. It can be referred to as Physically Based Rendering (PBR) or Physically Based
Shading (PBS). Depending on what aspect of the pipeline is being discussed, PBS is usually specific to shadingShading (PBS). Depending on what aspect of the pipeline is being discussed, PBS is usually specific to shading
concepts and PBR specific to rendering and lighting. However, both terms describe on a whole, the process ofconcepts and PBR specific to rendering and lighting. However, both terms describe on a whole, the process of
represrepres
enting assets enting assets
from a from a
physicphysic
ally accurate ally accurate
standpstandp
oint.oint.
What is PBR?What is PBR?
We can view the benefits of PBR from an artistic and production efficiency mindset, which are as follows.We can view the benefits of PBR from an artistic and production efficiency mindset, which are as follows.
What are the benefits?What are the benefits?
We as artists need to think differently about the maps that describe the attributes of a surface. There are new mapWe as artists need to think differently about the maps that describe the attributes of a surface. There are new map
types with rules and guidelines to follow.types with rules and guidelines to follow.
We need to throw out the concepts of diffuse and specular maps from traditional rendering workflows. These mapsWe need to throw out the concepts of diffuse and specular maps from traditional rendering workflows. These maps
only served as workarounds so to speak for approximating light interaction with materials. Advances in computeronly served as workarounds so to speak for approximating light interaction with materials. Advances in computer
hardware and rendering allow us to now more closely simulate the physics of light.hardware and rendering allow us to now more closely simulate the physics of light.
In PBR, the shader handles the heavy physics lifting through Energy Conservation and BRDF, while we as artists createIn PBR, the shader handles the heavy physics lifting through Energy Conservation and BRDF, while we as artists create
maps that are guided by physics principles. It takes out the guesswork of material values and allows us, as artists, tomaps that are guided by physics principles. It takes out the guesswork of material values and allows us, as artists, to
spend more time in the creative aspects of texturing. While it is important to adhere to guidelines and author mapsspend more time in the creative aspects of texturing. While it is important to adhere to guidelines and author maps
correctly, it doesn't mean that we now have to disregard our artist intuition. In fact, it’s the artistic perspective thatcorrectly, it doesn't mean that we now have to disregard our artist intuition. In fact, it’s the artistic perspective that
truly brings character to a material, revealing its story through carefully crafted detail and expression. It’s importanttruly brings character to a material, revealing its story through carefully crafted detail and expression. It’s important
not too get overly caught up in the physics. Just because we are working in a more physically accurate environment, itnot too get overly caught up in the physics. Just because we are working in a more physically accurate environment, it
doesn't mean that we can't do stylized art as well. For example, Disney's physically based reflectance model wasdoesn't mean that we can't do stylized art as well. For example, Disney's physically based reflectance model was
designed to be a "principled" approach meaning that it was geared more towards art direction rather than a strictlydesigned to be a "principled" approach meaning that it was geared more towards art direction rather than a strictly
physical model. So we should know the principles and utilize the guidelines, but not be slaves to them.physical model. So we should know the principles and utilize the guidelines, but not be slaves to them.
What does it mean for the artist?What does it mean for the artist?
Metal/Roughness WorkflowMetal/Roughness Workflow
The The
metal/metal/
roughnesroughnes
s s
workflworkfl
ow ow
is is
definedefine
dd
through a set of channels, which are fed asthrough a set of channels, which are fed as
textures to a sampler in the PBR shader. Thetextures to a sampler in the PBR shader. The
maps specific to maps specific to
the the
metal/metal/
roughneroughne
ssss
workflow are base color, metallic andworkflow are base color, metallic and
roughness as shown in figure 02 and we willroughness as shown in figure 02 and we will
discuss each of these map types in the sub-discuss each of these map types in the sub-
sections below. The PBR shader will alsosections below. The PBR shader will also
utilize ambient occlusion, normal and possiblyutilize ambient occlusion, normal and possibly
height for parallax mapping as shown inheight for parallax mapping as shown in
figure 03. These map types are common tofigure 03. These map types are common to
both workflows and will be discussed in theboth workflows and will be discussed in the
"Maps common to "Maps common to
both workflows" section.both workflows" section.
In In
the metal/roughnthe metal/roughn
ess workflow, theess workflow, the
reflectance value for metals are placed in thereflectance value for metals are placed in the
base color map along with the reflected colorbase color map along with the reflected color
for dielectrics and the reflection at grazingfor dielectrics and the reflection at grazing
Figure Figure
0202
1. It can be easier to create realistic assets as it removes the guesswork of authoring surface attributes such as1. It can be easier to create realistic assets as it removes the guesswork of authoring surface attributes such as
speculspecul
arity since arity since
the methodology and the methodology and
algoritalgorit
hms are hms are
based on based on
physicphysic
ally accurate formulas.ally accurate formulas.
2. Assets will look accurate in all lighting conditions.2. Assets will look accurate in all lighting conditions.
3. Provides a workflow for creating consistent artwork, even between different artists.3. Provides a workflow for creating consistent artwork, even between different artists.
vol.2 - Practical guidelines for creating PBR texturesvol.2 - Practical guidelines for creating PBR textures
Page Page
44
angles is handled by the BRDF. A metallic map is utilized,angles is handled by the BRDF. A metallic map is utilized,
which works like a mask to differentiate metal andwhich works like a mask to differentiate metal and
dielectric data found in the base color map. The dielectricdielectric data found in the base color map. The dielectric
F0 values are not authored by hand as the shaderF0 values are not authored by hand as the shader
handles them. When the shader sees black in the metalhandles them. When the shader sees black in the metal
map, it treats that corresponding area in the base colormap, it treats that corresponding area in the base color
map as dielectric and uses a 4%map as dielectric and uses a 4%
(0.04) reflectance value as shown in(0.04) reflectance value as shown in
figure 04. As we discussed in Volumefigure 04. As we discussed in Volume
One, the 4% value covers mostOne, the 4% value covers most
common dielectric materials. It’scommon dielectric materials. It’s
important to note that all values, suchimportant to note that all values, such
as dielectric F0, metal reflectance andas dielectric F0, metal reflectance and
brightness ranges for albedo color, arebrightness ranges for albedo color, are
derived from actual measured data. Asderived from actual measured data. As
we look at each map type, guidelineswe look at each map type, guidelines
will be discussed, which are based onwill be discussed, which are based on
measured data.measured data.
In Volume One, we discussed theIn Volume One, we discussed the
notion of energy conservation wherenotion of energy conservation where
the light reflected off the surface willthe light reflected off the surface will
never be more intense than it wasnever be more intense than it was
before it hit the surface. In terms ofbefore it hit the surface. In terms of
implemimplem
entatioentatio
n, n,
the the
shader typicallyshader typically
handles the control of energyhandles the control of energy
conservation, which is the case withconservation, which is the case with
Substance. With the metal/roughness workflow it is notSubstance. With the metal/roughness workflow it is not
possible to break the law of energy conservation. Thepossible to break the law of energy conservation. The
diffuse (reflected color) and specular balance arediffuse (reflected color) and specular balance are
controlled through the metallic mask, which means youcontrolled through the metallic mask, which means you
can’t create a situation where the diffuse and specularcan’t create a situation where the diffuse and specular
can combine to reflect/refract more light than is initiallycan combine to reflect/refract more light than is initially
received.received.
Figure 04Figure 04
Figure 03Figure 03
The reflectance value for metals are placed in the base color map alongThe reflectance value for metals are placed in the base color map along
with the with the
reflrefl
ecteecte
d d
color for color for
dieldiel
ectricectric
ss
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