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VRay Splotches


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#1 David Ghazawy

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Posted 16 March 2008 - 10:46 AM

Having some problems with Vray. Any advice you could offer would be appreciated.

*When rendering an image I was getting black splotches on one of the walls. I know this is caused by the lack of light - so I increased Secondary bounces roll out (from 3 to 10 - Is this the correct solution for the problem of splotches in Vray?). This has gotten rid of the splotches but I've encountered other problems because of this. I also increased the subdivs (using the Quasi-Monte Carlo GI)

- White faded lines running accross the screen (at the top only).
- In some areas where it's meant to be shaded it's actually over bright (I might have to
dial down the secondary bounces rollout
- A significant increase in rendering time (primarily for the Irradiance Map).
- Window bleeds the background colour into the room.

* Windows which fall perpendicular to the camera don't have any reflections. Does anyone know of a way to make these more apparent. The only way I can think of to do this is to apply a very light dirt texture to them, this will peal them away from the background (Alot CG interior design work I've looked have purposely placed the camera at angles to glass windows (or used some form of volumetric lighting/fog lighting) so as to avoid this problem.

* Objects in the distance have a noisy feel about them. The DOF plane is set to include them in focus so it's not the camera.

Thanks in advance

David Ghazawy

#2 Scythar

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Posted 16 March 2008 - 11:02 AM

Not bad for a first post :lol:

only one that could help you here i think is STU, so i would pm him to make sure he read this post.

#3 Stu

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Posted 17 March 2008 - 09:08 AM

wow... ummm not much i can help you with there as its all a bit vague to be honest. vray has a crazy amount of setting that could contribute to any one of those problems, so alot of the issues you describe can be reproduced several different ways.

just a bit of general advice for now though:

firstly, artifacts in your render can be caused by several things. first thing i would check would be that your mesh is clean and then that you do not have any double faces (ie one object accidentally placed over another) in your scene. then as you said, check the lighting and render settings which relate to image quality... problem solved anyways.

GI... secondary bounces, its not generally a good idea to increase it by such a substatial amount. this issue is probably the cause of you high render times. i rarely have it set above 1.5 and thats only if im desperate. the best solution to brighten your scene is to simply add more light. most likely this is also the problem with the over exposed area and maybe even colour bleeding at your windows.

thats about all i can give you right now.

if you could upload pictures of the faded lines, colour bleeding issues, material settings, render settings etc. then - possibly - i can help more.

even better, if you could upload your scene somewhere and pm me a link to it, i could definately help more by having a look at it and then pointing you in the right direction.


quick check though... what version of vray do you use? and is it a legal licensed version or a demo version?

#4 David Ghazawy

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Posted 22 April 2008 - 09:59 AM

Dear Stu

Thanks for the reply. Actually i worked out the problem while I was working on something else about three weeks ago (hence the late reply). It turns out I turned down the 'rays per sample' rollout to speed up the render time while I was constructing the set and applying textures (I was using the skylight light > problem was in the Cast Shadows section). So I turned these back up (upto 13, but 20 is usually the default on vray 1.5).


I'll take on board your suggested GI settings. I fixed all the other problems I had by reverting to my default interior Vray settings (except for the secondary bounces to take care of the splotches).

David

#5 _*Kamilla122_*

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Posted 23 June 2016 - 12:55 PM

Thank you for posting this information!)






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