Prerendering issue - black spots

[Jarda_viz]

Hi Kray friends,
does anybody know how to fix this problem during prerendering. There is glass and behind I can see some black spots on the wall.

[Janusz Biela]

Hello!

Try:
- increase amount of photons in Photon Tab. For example I use minimum 2.000.000. it is maybe a lot for small rooms but G. told me last time: then more the better for averaging information Photons cells. Here good setting for Photon Map:

- if you use Nodes turn OFF them ...maybe you use something unsupported
- if you use Dielectric Node change it for another system of glass
- all the time with problems in render use analyse tools:

it will show you errors from Photon Map side. If Photon Map is correct (photon map has good quality, gradient, no black holes, no missing photons) then problem is elsewhere.

[Jarda_viz]

Thanks Janusz for your tips.
I found out, that when I switch off reflection of the glass this problem disappear.

Glass node (standard) creates this problem
Dielectric material is OK.

[Janusz Biela]

ok!
I suggest not to use Dielectric Node - it affect errors in Photon Maps (very strong random Hot Photons)
Here my glass Node:

Eclipse_window_glass.srf

(47.61 KiB) Downloaded 202 times

Please notice bump map is in Y direction stretched very strongly (it is no mistake)
Also if you need stronger color, simple use color filter (the more the less transparency will be glass)
Do not use Refraction Index for windows glass!
Windows glass must be always in separate layer with Raytracing flag + of course no shadows.
You can add Refraction Index then will be glass for "glass effect"
Inside Node is limit up to recurse 6. It is enough but sometimes when is scene with many layers of glass you must increase this value up to 10-12.

[Jarda_viz]

Thank you very much. It works like a dream.

[Jarda_viz]

I found out, that if I use Standard material node it creates problems in some cases. Do you have the same experience? We use it very often to have one material set-up for LW (Kray) and Octane.

[Janusz Biela]

I found out, that if I use Standard material node it creates problems in some cases. Do you have the same experience? We use it very often to have one material set-up for LW (Kray) and Octane.

Hello

I use only Nodes in Kray render (I do not use standard LW setting at all) but in different way:
- no shaders (carpaint, Dielectric, SSS)
- only mathematician operators (multiply, mixer, add)
- fresnel of course (I suggest LW Fresnel)
- Normal map transformation and also ADD for them (too mix a couple bump maps)

My favourites Nodes:
- color tool (with out this render has no sense) save a lot of time
- LW mixer - very important for mixing textures
- curve (for making blending in velvet and bum drop off effect) actually one of the most important (also in V-ray)

Exeption for shaders:
- reflection LW Node with ani reflection
- reflection DP Node with glancing (but last time I drop this)

I suggest use LW Nodes if possible: almost 100% compatibility with Kray and no problems with network render.

[Jarda_viz]

Hello,
thank you very much for detailed explanation.
I tried last time this node set-up for the glass and it created above mentioned problem (black spots)

If I connect it directly it works well (second picture)

I had a problem only with glass surface so far. I have to test, whether this set-up could be use or not with KRay.

[Janusz Biela]

Use only direct connections. Also be careful with compound.