Transitioning from VRay to LuxCoreRender

Discussion related to the LuxCore functionality, implementations and API.
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B.Y.O.B.
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Re: Transitioning from VRay to LuxCoreRender

Post by B.Y.O.B. »

Can you show some reference images of what you have in mind?
Maybe even your current Vray output of these materials.
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Re: Transitioning from VRay to LuxCoreRender

Post by happyboy »

B.Y.O.B. wrote: Tue Jun 25, 2019 7:39 am Can you show some reference images of what you have in mind?
Maybe even your current Vray output of these materials.
For example this floor tile:
Image

And a more "obvious" floor:
Image

Many bathrooms use them on both floors and walls:
Image

All three pictures are found on the Internet.
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Re: Transitioning from VRay to LuxCoreRender

Post by B.Y.O.B. »

I would use a glossy material with lowest roughness (around 0.001).
The rest comes down to having the right diffuse textures. Do you have image textures or do you want to do them procedurally?
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Re: Transitioning from VRay to LuxCoreRender

Post by happyboy »

B.Y.O.B. wrote: Tue Jun 25, 2019 3:43 pm I would use a glossy material with lowest roughness (around 0.001).
The rest comes down to having the right diffuse textures. Do you have image textures or do you want to do them procedurally?
I have diffuse textures, and I'm also using lowest roughness, and then? I tried to adjust IOR, leaving other parameters intact, but it seems to be quite different from VRay's setting (i.e. with the same IOR the render is quite different). Do I need to adjust other parameters?
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Re: Transitioning from VRay to LuxCoreRender

Post by B.Y.O.B. »

Can you show your result, and your expected output (Vray result) for comparison? Without images it's hard to guess what might be wrong.

Here's my result (10 s + denoised)
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Re: Transitioning from VRay to LuxCoreRender

Post by FarbigeWelt »

happyboy wrote: Tue Jun 25, 2019 4:08 pm I tried to adjust IOR, leaving other parameters intact, but it seems to be quite different from VRay's setting (i.e. with the same IOR the render is quite different).
LuxCoreRender use physical correct IOR means c_in material/c_in vacuum, c is speed of light.

If you like correct simulations, define internal and external volumes. Start with clear volumes. If you use volumes do set world volume and camera volume, e.g. IOR air (external) and IOR material (internal) maybe crown glass. There is node with IOR values. The volume definition may take some additional time but it is the way to render water in a glass for example.
Light and Word designing Creator - www.farbigewelt.ch - aka quantenkristall || #luxcorerender
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Re: Transitioning from VRay to LuxCoreRender

Post by B.Y.O.B. »

Volumes are not needed for marble (unless it is very thin and you need the SSS effect, for example on a statue).
Anyway, the IOR in the glossy material is just a simple multiplicator for the specular color. It does not take the interior/exterior volume IOR into account. It can be used if you know the IOR of your glossy coating, for example if you have a surface with a water film, you can use the IOR of water (1.33) and set the specular color to (1, 1, 1).
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Re: Transitioning from VRay to LuxCoreRender

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B.Y.O.B. wrote: Tue Jun 25, 2019 4:25 pm Can you show your result, and your expected output (Vray result) for comparison? Without images it's hard to guess what might be wrong.

Here's my result (10 s + denoised)
ahhh.... sorry. After some checking it turns out that MY .scn generator program had a bug that messed up things. I used my program to tune paramters instead of BlendLuxCore so I didn't realize it sooner. Next time I'll make sure to experiment in Blender first.

Now back to the "artificial light source" problem I mentioned in my original post. I finally solved it. First, I simply used "invisible to camera" (in Blender) but it still cast shadows and appears in the mirror as a white rectangle. Later I manually changed .visibility.indirect in the light object's material, the shadow is still there and it became BLACK in the mirror. After searching in the forum I found the transparency setting. After setting transparency.front = transparency.back = 0 0 0 the light object dispeared completely (including in the mirror) without casting shadows, which is what I want.

I thick this is most people is thinking about when trying to "hide the area light", so is it possible to expose it directly in Blender's Area Light settings? For both VRay and Cycles, it's far easier to do this. In VRay it's just a single click "invisible", and in Cycles though I think you have to turn out some ray visibility in blender, but I found that very soon. However in LuxCore I found the solution after 2 days :-S
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Re: Transitioning from VRay to LuxCoreRender

Post by happyboy »

FarbigeWelt wrote: Tue Jun 25, 2019 6:01 pm If you like correct simulations, define internal and external volumes. Start with clear volumes. If you use volumes do set world volume and camera volume, e.g. IOR air (external) and IOR material (internal) maybe crown glass. There is node with IOR values. The volume definition may take some additional time but it is the way to render water in a glass for example.
Thank you! Though I'm not doing volums right now, your suggestion would definitely help me later!
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Re: Transitioning from VRay to LuxCoreRender

Post by B.Y.O.B. »

happyboy wrote: Wed Jun 26, 2019 2:38 am Now back to the "artificial light source" problem I mentioned in my original post. I finally solved it. First, I simply used "invisible to camera" (in Blender) but it still cast shadows and appears in the mirror as a white rectangle. Later I manually changed .visibility.indirect in the light object's material, the shadow is still there and it became BLACK in the mirror. After searching in the forum I found the transparency setting. After setting transparency.front = transparency.back = 0 0 0 the light object dispeared completely (including in the mirror) without casting shadows, which is what I want.

I thick this is most people is thinking about when trying to "hide the area light", so is it possible to expose it directly in Blender's Area Light settings? For both VRay and Cycles, it's far easier to do this. In VRay it's just a single click "invisible", and in Cycles though I think you have to turn out some ray visibility in blender, but I found that very soon. However in LuxCore I found the solution after 2 days :-S
At some point in the past the area light transparency was exposed in the old Blender addon. But it is not the "officially approved" method, and it can cause artifacts in some rare circumstances, so I did not implement it in BlendLuxCore when I did the rewrite of the addon.
Maybe I will consider to add it again in the 2.80 version of the addon.
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