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  1. #281
    doo,this is called the extinction coefficient and is part of a complex index of refraction.the k3 in the paper is for the 3rd substrate layer k (3).the complex IOR is used for conductive materials as metals.since this is not part of my thin film code rebuild,i have started another thread with test with a complex IOR code for Metal mats.

    the k value in the thin film rebuild is was a first test with a beer lambert absorbtion equation,that is not usefull atm and should left at 0.i have forgotten to take it out before posting.so dont use it

    here the link for the metal conductor shader code,further explanation in that thread
    https://blenderartists.org/forum/sho...nducter-shader
    Last edited by pixelgrip; 18-Nov-17 at 15:42. Reason: typo



  2. #282
    more brain food.i found this paper about diffractive surfaces.

    https://arxiv.org/pdf/1705.06086.pdf



  3. #283
    Member Secrop's Avatar
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    Originally Posted by pixelgrip View Post
    more brain food.i found this paper about diffractive surfaces.

    https://arxiv.org/pdf/1705.06086.pdf
    I devoured this paper a few months ago, along with some others in the same scene... The only problem with these calculations is that they must be implemented in the render kernel. There's no way to implement them either with OSL or with the SVM. This was probably the main reason I quit trying to achieve these effects, and dedicated a bit of more time trying to understand Cycles and Blender source code (on which I still have a long path to travel).



  4. #284
    Secrop,i see.but since moony was working on his roughness build,i think its always helpfull to see ,what math are used in some papers.sometimes there are golden code gem snippets in it.

    a few months ago no thinfilm build was there,now we have at least two builds,a metal shader and moonys roughness build too.maybe someone can make use of a code in the papers,if not this paper may be the next.



  5. #285
    Member Secrop's Avatar
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    I'm not trying to negate all these works... Actually I think it's really nice to see people diving into them.. I'm just pointing the fact that even if we get the math right, the kernel will mess with the results in the end.

    Roughness still doesn't account for the outgoing direction as we don't have access to it, and even if we trick it like I've done with my diffration grating shader, there are discrepancies in the total reflected energy. The same goes to the Metal shader when roughness is used.

    Another problem is the sampling algorithm from cycles does not allow these 'scratched highlights' or other high-intensity localized reflections (like moony's sparkling snow). So even if we have an anisotropic element crossing some pixel (which will reflect much more light in that same pixel), the current blending of sampled information will wash that out, and the result will be a dull roughness... :/



  6. #286
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    Originally Posted by Secrop View Post
    So even if we have an anisotropic element crossing some pixel (which will reflect much more light in that same pixel), the current blending of sampled information will wash that out, and the result will be a dull roughness... :/
    Indeed - what we need is something like this:

    https://rgl.epfl.ch/publications/Yan2014Rendering

    Perhaps once all the current focus optimisation is complete - we'll start getting new features like thin film, microroughness and glint options directly implemented in Cycles shaders.



  7. #287
    these glints, in the paper, looking good and fast.whats about Blender 2.8,are they keeping the previous cycles shader ,or are they planing implementing new improvings shaders too (or even better the cycles core engine)?
    if you see how good even a gameengine like unity can (with megascan ie)look like in realtime,it would be nice to see some improvement boosts in the cycles /2.8 render engine,at least all shortcomings).
    also nice would be cie xyz for cycles,if someone want wavelength calculations with it.
    Last edited by pixelgrip; 14-Dec-17 at 16:07.



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