Artifacts, interior rendering

[martinengdahl]

Heya!

 

Anyone know whats going on here?

Im also puzzled by the blotches on the ceiling and walls and so on. I know the bottom part looks crap because I stoped the render :-)

Im pretty new to Vray, so I dont know even where to begin looking.

 

EDIT: Im using Rhino 5 and Vray 1.5

Edited April 19, 2013 by martinengdahl

[Ismael]

The worst tutorial you'll find on a web search will yield a pretty decent image over the one you show many times over.

Here is one similar:

 

http://www.evermotion.org/tutorials/show/7900/making-interior-scene

 

learn from that tutorial and apply to your scene what you learned.

[martinengdahl]

I think you misunderstand the question:

I am not asking how to do a good render, I am asking why those artifacts show up? I have done a bunch of renders with vray that look pretty good, but I have never encountered those blotches and jagged seams in textures before; I would like to know why they appear so that I gain knowledge on how to set up renderings in the future.

[Ismael]

Oh! Sorry, I thought you said, "Im pretty new to Vray, so I dont know even where to begin looking."

I had no idea you had done a 'bunch' of renders...

[martinengdahl]

I have used it for a month, done about 10-15 tutorials and gotten good results when trying to apply the knowledge to other projects. This is the first time I encounter this problem, which is why Im asking. Thanks for trying to help though :-)

[beestee]

Skylight portals could help at the windows, for more info see "Options" -> "Light portal" in the help files. If that is not enough, you will probably need to look at increasing your samples for the indirect illumination settings, also found in the help files:

 

I get splotches in my rendering when using the irradiance map

 

There may be several reasons for splotches when rendering with the irradiance map:

• Regular noisy splotches
  - these are usually a result of insufficient Hemispheric subdivisions for the irradiance map. Usually they appear in difficult lighting situations when the default setting is too low. Examples of difficult lighting conditions are small bright sources of indirect light, hdri environments etc. You can avoid these splotches in several ways:
  
  
  • If you are using Deterministic Monte Carlo GI for secondary GI bounces, try using another method - the
    light map
    or the
    photon map
    .
    
    
  • Increase the Hemispheric subdivisions for the irradiance map. Note that the effect of the increased subdivisions depends also on the settings of the
    DMC sampler
    .
    
    
  • Decrease the Noise threshold of the
    DMC sampler
    .

Edited April 19, 2013 by beestee

[Francisco Penaloza]

Those blotches are the typical result of low GI setting, you need 2 things as mentioned by Benjamin, more light in to your scene, better GI.

Here is a good read.

http://www.spot3d.com/vray/help/150SP1/render_params_advancedimap.htm

 

http://www.spot3d.com/vray/help/150SP1/render_examples_advancedimap.htm

 

http://www.spot3d.com/vray/help/150SP1/render_params_lightmap.htm

 

http://www.spot3d.com/vray/help/150SP1/examples_lightcache.htm

[Crazy Homeless Guy]

A quick fix might be as simple as changing the way your Irradiance map samples the Irradiance information. Try switching the Advanced setting to what I am showing in the attached image.

[martinengdahl]

Thanks for all the great advice guys, I got rid of the weird stuff but there is something else nagging me a bit (and has for some time): when using HDRI for my GI, I get these funky circle reflections/refractions on glass surfaces. Look in the upper right corner to see what I mean. Any ideas what this is? I have used several different HDRI maps, and they all end up the same.

[beestee]

The circles reflecting in the glass look like the light fixtures to me. They appear correct to me. I do see some leaks though. You might try turning on "Check Sample Visibility" in your irradiance map settings.

[martinengdahl]

Thanks for all the replies, guys! All sorted and going well :-)

[martinengdahl]

It seems I was a bit hasty...

This is a better example of the glass artifacts I was talking bout, anyone know what it is and how I can fix it?

[beestee]

The problem is much easier to see now. I imagine the issue is coming from the IOR (Index of Refraction) calculation.

 

Found this on the chaosgroup VfR forums:

 

With glass you will need to have your glass modeled as solid. Once you have that you will need to add refraction to your material (make sure the transparency of the diffuse layer is at 100% or white). This is the recommended physically correct way to make glass. For better architectural glass enable Affect Shadows and Affect Alpha in the refraction layer.

 

The glass object being a solid would most likely ensure that you had the two planes with opposing normals that are necessary for the IOR calculation.

 

In this tutorial, starting on page 5, there is a description of how to make a fake glass material that can be applied to single planes. This would in effect bypass the IOR calculation if that is in fact the issue. It also goes on to describe the need for two planes with opposing normals for proper refraction calcs.

[martinengdahl]

Hmm... the glass is now a box extruded from curves, is that different from a solid box render wise?

Thanks for the link, going to read it now!

[martinengdahl]

I tried "disable volume fog" in the glass material, and that seems to have fixed it. Will try a render.