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Physically Based Rendering in Vectorworks


zoomer

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For those that are interested in PBR from a technical standpoint,

here are a few links to Materials from Siggraph 2015 :

 

http://blog.selfshadow.com/publications/s2015-shading-course/

especially this PDF- semi dry, but colored and illustrated at least :

[slides]

 

Quite technically :

https://www.allegorithmic.com/pbr-guide

 

Or in You Tube doses for internet generations :

 

 

Looking forward to the discussion, example materials, questions etc.

 

Edited by zoomer
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There are a lot of Videos with a more practical approach  :

 

 

I think that video is quite compressed and covers the most important things in an entertaining way.

 


 

 

This is a Blender Tutorial.

Beside the Marionetteish Material Setup there and not 1:1 convertible, it shows shows some nice aspects of PBR.

 

 

 

So I add the second Part for Metals :

 

 

 

 

and his general overview over photorealistic Rendering :

 

 

Edited by zoomer
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So there are just a few simple cardinal rules you have to keep in mind when setting materials.

 

Absorption :

The sum of  Diffuse + Reflection + Refraction has to be (far) less than incoming light

(Important for light distribution in global illumination calculation)

 

Everything has Fresnel :

Reflection is depending on angle of incidence. Specular Reflection is 100 % at glancing angles.

 

Difference behavior between Dielectrics and Metals :

White vs colored Reflections, Diffuse vs no Diffuse, ranges of reflection amounts

 

Image Textures from Photos don't give usable values for the Diffuse Channel.

Instead they show the end result of a Material in a certain environment and exposure.

 

A physical correct Material works universal in all environments. You will have to set the

final image brightness range by camera exposure like you do in reality, to adapt to a certain

environment.

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So Reflection is very essential for a materials characteristics.

 

Refractiveindex.info provides measured data in r + n values. It has even a section for some materials

used in rendering.

As some renderers like V-Ray prefer to control Reflections instead by IOR values (Index of Refraction)

I took all relevant data from Refractive Index and made a little table that converts the Reflection values

into "V-Ray" IORs to set my Materials in V-Ray :

 

EDIT :

Note that, beside the Dielectrics, the resulting Metals IORs are no physical IORs.

It is just the way to get the Reflection Values for V-Rays IOR Setting System.

It is just about the Reflection Values at 0 degree.

 

Screenshot-30.jpg

 

Given Reflectance shows values when looking perpendicular at a surface.

(When looking along a surface you will always have 100% Reflection (Fresnel))

 

As you can see :

 

1.

As long as you don't want to render semi conductors like silicon or e.g. speckles of minerals in a granite,

Reflection values between 20-50 % are taboo.

 

2.

Metals have quite visible differences in amounts of Reflection from 50-96%.

You will rarely deal with pure metals in Architecture though.

 

3.

Most of our Materials used are Dielectrics. These have very similar amounts of Reflection that you can

hardly differentiate. That is why a new V-Ray Material defaults to in IOR of 1.6 (about 5% Reflection) which

works in 98% anyway.

Edited by zoomer
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And to finde the bridge to VW again, I did a Material Test from scratch.

 

Materials are thought to be, from left to right from top to bottom :

(no camera so far, so no exposure and brightness a bit low for a "white" gypsum)

- white glossy plastic

- red semi glossy plastic

- aluminium brushed

- gypsum

- concrete glossy

- polished steel

 

MAT_TEST_01.jpg

 

Not 100% convinced so far.

but you could compare using VW standard metal/plastic/ ... reflection shaders.

I like faking Fresnel with Glass Shader better.

File Attached.

 

 

 

 

BTW,

here the 2016 Reflection Model. You can compare.

I don't really know what I will prefer.

 

MAT_TEST_01_2016.jpg

 

 

VW_MAT_TEST.vwx.zip

Edited by zoomer
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And what does C4D when I replace VW legacy reflection with the GGX reflection shader.

I like it more. Still no exposure and I think there is some brightness clamping of the differences

of both metals.

 

MAT_TEST_01_C4D.jpg

 

 

Edit :

C4D with exposure. I think I like it :

 

MAT_TEST_01_C4Db.jpg

Edited by zoomer
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Yes it will look different.

I think the C4D import is meant for those who don't want to spend time on creating own

RW Textures and prefer to buy a collection of "RW Textures. C4D Material Collections

will extend the Presets available for "RW Textures".

Just a bit of corrections needed after import.

 

But in these easy examples, where I am more interested in a physical "real" approach for

realistic GI light distribution, than an aesthetic one. It is hardly noticeable that a complex shader

has a real fresnel curve, while VW's glass Shader looks to be like a simple linear gradient.

 

For the plastic, I can not really quantify what looks "better" or more pleasant.

It will be more obvious in more complex materials like semi glossy floors, where reflections

and glossiness, depending on viewing angle, will decide if it looks like a puddle or like a linoleum.

 

 

 

 

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  • 1 month later...

I come to the conclusion that it is not very productive to force RW to do a physical based render workflow.

See this thread as a source of information only, that may help when running into individual problems in rendering,

like flat looking GI or unnatural reflections.

Use PBR only in render systems that support PBR completely. For RW such a PBR workflow will generate more

problems than it solves.

 

When you want friendly bright white Materials, feel free to use color pure white 255/255/255.

Luis M Ruiz did some nice examples with the church that look gorgeous.

Pure white will also work in most GI cases as there may be enough other surfaces that absorb light and this

way it will work better in non realistic render modes like shaded or OpenGL by default. Without the need of a

"calibrated" camera exposure and light setup.

Even for C4D export, the brightness reduction workaround by adding a filter color will not go through and you

have to set colors there again anyway.

Similar for reflections. Trying to fake fresnel by using glass shader may not always look better and is much more

tedious than just using one of the plastic options with old specular or even metal options with its self illumination.

If you think your plastic needs 60% reflection in your scene to look like you want or your polished metal need

diffuse color brightness, do so. 

 

For me PBR in PBR environments make things just easier, more predictable and your material settings will work

in any scene again. In RW an understanding of how materials work an certain realistic settings can help in some

cases but don't overdo and try to force it in that way.

 

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