Question regarding Mix-Node (Color Math)

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Mael2
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Joined: Sun May 16, 2021 3:05 pm

Question regarding Mix-Node (Color Math)

Post by Mael2 » Sun May 16, 2021 3:50 pm

Hi,

at first I have to say, that I am quite new to blender, luxcore and 3d in general. So maybe I get something wrong or I just don't know how to do it. Please have patience with me :D

Here is my question:

I try to combine 2 different roughness maps to give the material even more variation. So my plan was to use the color-math node and switch the mode to "mix". As I understand "Fac" regulates how much of which rougness map I can see. When I try to do the same in cycles I use the mix rgb node and it offers even more blending modes like "overlay" which seems to give more the result what I am looking for. For me it seems that "overlay" gives a better representation of both roughness maps at the same time. Is there something similar in luxcore like "overlay"?

I attached 2 pictures and maybe you can see what I mean.

Many thanks in advance!
Attachments
K1600_Cycles_Test.JPG
K1600_Luxcore_Test.JPG

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Dade
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Re: Question regarding Mix-Node (Color Math)

Post by Dade » Sun May 16, 2021 4:02 pm

Classic bump mapping is not additive (i.e. if you add/mix 2 bump maps, the result is not the sum of the bumps). So operations over many bump maps are not very intuitive. There have been alternative solutions proposed over the years but pretty much everyone are still using the same classic bump mapping algorithm.

Said that, you can just pre-process the bump maps in Gimp/Photoshop/etc. and then use the baked result. There is is really no reason to mix the images at rendering time if you can mix them as pre-processing (i.e. pre-processing is faster). I think you can even bake the mixed bump maps in Cycles and than use the result in LuxCore.
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B.Y.O.B.
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Re: Question regarding Mix-Node (Color Math)

Post by B.Y.O.B. » Sun May 16, 2021 4:09 pm

You can google how the "overlay" algorithm works in detail (it should be a rather simple equation) and perform it with math nodes.
For example here: https://www.deepskycolors.com/archive/2 ... modes.html

@Dade: Mael2 is talking about mixing roughness maps, not bump maps.

Mael2
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Re: Question regarding Mix-Node (Color Math)

Post by Mael2 » Mon May 17, 2021 4:50 pm

Thank you very much for your response. I will try to recreate it with the math nodes but I am a little sceptical that I'll succeed (I am such a noob :D).
Is there a possibility that more blending modes will be added in future releases?

I want to thank you for providing such an incredible render engine and all that for free! I hope luxcore will get more attention in the future as it deserves it.

Martini
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Re: Question regarding Mix-Node (Color Math)

Post by Martini » Tue May 18, 2021 3:33 pm

Mael2 wrote:
Mon May 17, 2021 4:50 pm
I will try to recreate it with the math nodes but I am a little sceptical that I'll succeed (I am such a noob :D).
I did this once. I just want to prepare you what it looks like, as BlendLuxCore does not support NodeGroups... :shock:
LuxCore-overlay.png
Before you ask, no, I don't still have the .blend file :cry:
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sarmath
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Re: Question regarding Mix-Node (Color Math)

Post by sarmath » Wed May 19, 2021 12:09 am

Hi. I would like to join this request for more colormath blending modes as using math nodes is not user friendly. Just check how many operations has mixrgb in cycles. I am really missing overlay and screen modes🙂
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