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Timaphillips

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Reply with quote  #1 
Master Bathroom (combined 2).jpg 

I feel like I've tried a lot of different things to eliminate blotches and weird shadowing in corners and random areas. I've read around here they can be in random places and difficult to totally eliminate. Attached is a QMC render (you can see some grain on the mirror). QMC took nearly 2 hours (on a 4790k CPU) for what I think is a pretty basic model with VERY few lights. High preset produces worse random bright blotches and default is unusable (but only 8 minutes render time).

Also, notice the reflection on the mirror on the left side of the towel holder. The reflection is white, and I'm thinking it's only reflecting the white painted wood trim around the mirror. Just couldn't get this to reflect properly.

Some notes:
1) Wall and ceilings are 5" thick and I've made sure to orient faces correctly. I'll double check when I get home today again.

2) I've blended in a SketchUp "Hidden Line" style using a "multiply" technique in GIMP. It's only about 8%. Help give corners a more definitive edge, especially at the cabinets and tub front. I'm sure maybe around here are familiar with the technique. 

3) Light sources are natural sun from the windows and the wall fixtures. Fixtures are two identical fixtures form the podium browser. I had to lower the light power to .25 on each omni (3x omni's per fixture), which seems crazy low to me. No LEM's anywhere. Is this because the mirror is reflecting the light and multiplying it?

Also would love any input and tips for the scene!

Nick00

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Reply with quote  #2 
Hi there, can you post you render with the high preset? It does seam your model has an issue with blotches, we haven't seen a lot of them happening with QMC and high preset...

2 hours is really reasonable for a high quality interior render. If you want to reduce the grain, render at a hier resolution and size if down after.

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Timaphillips

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Reply with quote  #3 
Both images are straight out of Podium. No post-processing or overlays. Both are viewport resolution from my 1440p monitor, which ends up as 2470 x 1234. To my eye, HIGH has shadowing included which makes the image much better and adds depth to raised objects, but still suffers from blotches. 

You'll notice in this one that I've added some cans which somehow go moved out of scene on the QMC render. Again, also no post-processing any sort. 

I've also attached the model if you want to take a look. I'd love some feedback on any basics I'm missing or any improvements I can make to my technique.

Interior Default 2.1- HIGH (44 minutes)

Master Bathroom- High.jpg 

Interior Default 1.05 (8 minutes)

Master Bathroom- default.jpg 

 
Attached Files
skp Master Bathroom.skp (27.01 MB, 5 views)

bigstick

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Reply with quote  #4 
This is tricky. The interesting thing is that the blotches are in the same places with different presets. This would tend to indicate that there is something in the scene causing it.

There's no question that the scene is over-lit. I think the light sources are too powerful with lots of reflective surfaces which is causing problems for the algorithms.

Try reducing the light power. If these lights are from the Browser, have you modified them?

The difficult thing with rendering is that we are trying to produce something which approximates something that doesn't exist in the same form in real life.

Our eyes constantly do a real-time equivalent of Photoshop's auto-levels adjustment and stitch segments of what we see together. It's the difference between taking a photo that looks too dark and the image we perceive which generally looks brighter. The photograph is correct, we don't have the equivalent of a 'raw image mode' for our eyes! Interiors generally are a lot darker than we think they are.

Therefore the solution is to try to get the lighting similar to how it would be in reality, and boost the brightness in PIE. Maybe turn SU shadows off too.

With less light bouncing around, the render algorithms should cope better.

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Timaphillips

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Reply with quote  #5 
Shadows OFF with Interior Default. The lights are obviously not adding much additional light at all. And the sliders for the sun was both at minimum on the above images. 

Is it best to always render with shadows off and rely on omni's LEM's instead? The fixtures over the mirror are set to a paltry .05 and the cans are .25.

Master Bathroom 2017-04-21 09093400000.jpg 

And this one is shadows off, interior default. Fixtures over the mirror at .5 and cans at .5. I'm thinking reflections really play havok on things... Blotchfest 2017. 

Master Bathroom 2017-04-21 09244000000.jpg 
And finally, here I've removed one of the mirror fixtures, thinking it's just too many for the space. Same brightness settings as above.

Master Bathroom 2017-04-21 09412100000.jpg 

Attached Images
jpeg Master Bathroom 2017-04-21 09244000000.jpg (193.51 KB, 0 views)

bigstick

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Reply with quote  #6 
I'm not sure what's going on here. It's always better to leave the render info bar on when you want comments, because it helps us to see what is going on.

If you have an interior view, and you can't see the exterior background, or it isn't important, put the sun intensity and exposure sliders up to max, because it lets more light into your scene.

Generally start with interior default renders if you don't have huge windows. Use interior brighter if you really need a brightness boost.

What is probably happening is that you are right about the reflections are causing the issue. What level of refection are you using? I only use 10 for glass. For Chrome and mirrors, you shouldn't need any more than 70-80%. I find that anything over that is too much.

You may have too many surfaces that are just too reflective. Many people tend to make their scenes over-reflective, and some of the Browser items also suffer from this.
Start with the the interior high preset with max intensity and exposure after checking your materials settings, and we'll take it from there. 

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Timaphillips

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Reply with quote  #7 
Did a quick test with sun sliders all the way up just to see the natural light and now whatever I try to put the sun sliders to, it's just keeps the same insane light intensity. A test render of "preview" showed normal lighting but then when I put it back up to High, the attached image was the result after wasting 45 mins of render time. Just failing left and right over here...

Master Bathroom 2017-04-23 16475800000.jpg 


Master Bathroom 2017-04-23 16490700000.jpg 

Timaphillips

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Reply with quote  #8 
And just ran a "preview," of the same larger resolution and lighting is normal again.

Master Bathroom 2017-04-23 17340200000.jpg 

bigstick

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Reply with quote  #9 
No blotches!

Hmm - strange. You might want to try using an HDR preset. See here for more info.

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Timaphillips

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Reply with quote  #10 
Quote:
Originally Posted by bigstick
No blotches!

Hmm - strange. You might want to try using an HDR preset. See here for more info.


Yes, no blotches...AND on preview, which is something good indeed. Did I find a bug, though? All I did was a test with the sun sliders all the way at 100% just to visually see the effect. Then I was going to run one at minimum and note the differences. Now the High preset is totally blown out. 

Downloading the HDR preset's now. Thanks for that. 
bigstick

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Reply with quote  #11 
There's no bug as such that I can see. It's the limitations of a preset-based approach. Some scenes are much trickier than others.
What we've been trying to do is work out what we need to do to make the presets work better with your scene.

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