zoomer Posted November 9, 2016 Share Posted November 9, 2016 (edited) 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 November 12, 2016 by zoomer 1 Quote Link to comment
zoomer Posted November 9, 2016 Author Share Posted November 9, 2016 (edited) 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 November 14, 2016 by zoomer Quote Link to comment
zoomer Posted November 9, 2016 Author Share Posted November 9, 2016 (edited) I think that is a quite nice essence of PBR in text form : https://www.marmoset.co/toolbag/learn/pbr-theory Edited November 14, 2016 by zoomer 1 Quote Link to comment
bcd Posted November 9, 2016 Share Posted November 9, 2016 Thanks Z, A little homework for the train. Looks very interesting. Quote Link to comment
rDesign Posted November 9, 2016 Share Posted November 9, 2016 @zoomer- Thanks for sharing these links, there's a lot of info in there. Quote Link to comment
zoomer Posted November 11, 2016 Author Share Posted November 11, 2016 (edited) 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. Edited November 11, 2016 by zoomer Quote Link to comment
zoomer Posted November 11, 2016 Author Share Posted November 11, 2016 (edited) 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. 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 November 15, 2016 by zoomer Quote Link to comment
zoomer Posted November 12, 2016 Author Share Posted November 12, 2016 (edited) 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 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. VW_MAT_TEST.vwx.zip Edited November 12, 2016 by zoomer 2 1 Quote Link to comment
zoomer Posted November 12, 2016 Author Share Posted November 12, 2016 (edited) 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. Edit : C4D with exposure. I think I like it : Edited November 12, 2016 by zoomer 1 Quote Link to comment
Markvl Posted November 15, 2016 Share Posted November 15, 2016 Great stuff @zoomerThanks for sharing. Quote Link to comment
grant_PD Posted November 16, 2016 Share Posted November 16, 2016 I think this also illustrates that even if one can import the textures from C4d into Vw, you are not going to get the same results. Quote Link to comment
zoomer Posted November 16, 2016 Author Share Posted November 16, 2016 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. Quote Link to comment
zoomer Posted January 12, 2017 Author Share Posted January 12, 2017 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. Quote Link to comment
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