Grainy Reflections

[hsa]

I am just starting to venture into the world of interiors and have run across a problem I just can't seem to find a solution for. For the life of me I can't seem to get rid of the grainy reflections depicted in the attached image. I am using a simple sky portal coming from the side. I have turned the glossy samples up to 48 on the floor material but still grainy. Any typical suggestions for handling these things?

 

Thanks

[CJI]

We Need some more information. Are you using Mental Ray? What shaders are you trying to use? Sky Portal Settings. Is there are bump map on the floor?

[hsa]

It is a standard A&D material with a glazed ceramic tile preset. My lighting is setup with a MR daylight system and I am using sky portals. My FG settings are set to low. This is FG only....no GI

[CJI]

Is there alot of grain throughout the render, Could you perhaps render something a little larger for a closer look?

[hsa]

There is grain on the walls as well. Pretty much everywhere there is a reflection I have grain.....Not sure if this is a material issue or a render settings issue

[CJI]

Try upping the samples in the portal light that could help.

 

Or in the A&D shader open the Fast Glossy Interpolation tab and change the Interpolation grid density to 1(same as rendering).

 

Ticking Fast interpolation next to reflection could help but note that this is less accurate.

 

I personally find the standard mr portal light to be too grainy and causes too many problems. so i unlocked the advanced shaders option in the portal ight and the Architectural Portal Environment shader for it which dramatically speeds up the Portal Light and cleans it right up.

 

This thread here should help with that. http://forums.cgarchitect.com/38854-render-times.html

 

Let me know how you get on.

[hsa]

I am actually using the same portal shader you mentioned. I think I might need to just tweak the glossy and reflective numbers a bit or maybe try different combos of those settings

[pixelperfectg]

You say you're using 48 samples on the A&D reflections however you didn't state what the glossiness value was set to. If glossiness is rather low like .35 or less then you will need far more samples than 48 to clear the reflection noise.

 

Of course there are other things you can do help with the speed/noise such as using interpolated glossy reflections or blurring the environment.

[hsa]

After tweaking the settings (bumped the glossiness up) and changed the fast glossy interp. settings I got a better result :-) Should have experimented a bit before starting a thread I guess. But hey this is how ya learn (lol)

[Peter M. Gruhn]

I've made a test scene kinda like yours and my renders are kinda like yours so I'm comfy with it.

 

Changing portal shadow sampling does make a difference in the glossy reflections, but (for purposes of analyzing the reflections) stopped helping at 32. Will test again with higher glossy settings. It's more a case of there being two kinds of noise and at lower shadow samples, the portal noise is more obvious with the glossy noise. I don't think the actual glossy noise changes at all.

 

Checking AA right now. Went from defaut (1:4 Box iirc) to Cranked allaway... it does help, but it's expensive.

 

Turned on fast glossy, but it blurred over the grout. That's bad. Tweaking settings there seems to get me closer to the original problem. I don't see this being the right direction. Had to try, eh?

 

Right, crank samples from 8 to 64... wow, of marginal utility.

 

On a hunch I'm turning off the bump map... vast improvement. Thought maybe. Those speckles are glossy reflection speckles, they are tiny bumps in the floor speckles.

 

You're using real world map size, aren't you? You change the tiles to, oh say 36" but deep inside there's a Speckle or two and their size hasn't changed and they suddenly become very small. Not familiar with the mapping between the unitless procedurals and realworld, I just jacked the .1 to 10 and saw improvement. So then I make a new tile material and leave its size be. Back to the room and turn off real world there and just make the uvw 36" and let the material render they way it thinks it is supposed to. And walla, I get a different look in the floor and better, more responsive glossies.

[hsa]

It is hard to say what fixed my problems because I changed several things at once (lol). I upped the glossy setting, tweaked the reflective setting and changed the grid density to 1 (same as rendering) while bumping up the look up neighboring points to 6. While it can be difficult to dial some of these things in you are glad to have so much flexibility to do things once you figure it out.....I will do a larger render this morning and post it