"splotchy shadows"

[Hoop]

Hi Everyone,

I've been helping a friend with some interior renders, which I'm new to doing since I typically do product renders. I can't seem to get the shadows smooth in the interior renderings. I've turned the Subdiv Mult up to 7.5 in the QMC sampler and even turned up the subdivisions and samples in the Irradience map both to 50. As you can imaging, doing this really shoots up the render time. The attached image is a close up in a room of what i'm getting. See near the baseboards and along the ceiling how "splotchy" and uneven the shadows look. I'm using a Global Illumination and all interior lights have a samples turned up to 30. Any idea what's causing this and how to correct it?

thanks,
Hoop

[Micha_cg]

"splotchy shadows"

I would say, set all subdivs values back to default. The splotches looks like IM artefacts. Most it help to use more samples. Try 128 IM GI samples or 256 or 512. I'm not sure you what the IM subdivs do, but be careful - the limit should be 50 ... 70. Try to stay at 20 ... 30.

Subdivs values of lights helps against shadow noise, but here is no noise visible.

I'm not sure it is the fastest method, but I work in full adaptive mode allways. Than you can forget all subdivs values most. Only you need to control the noise threshhold - 0.05 fast preview ... 0.005 super quality.



If you use the arealight option "store with IM" and you get splotches, than you should set the arealight subdivs at 9 or 12 or 16. The full adaptive mode don't control the IM passes, so you need this little extra settings here.

[Hoop]

"splotchy shadows"

Micha,

thank you very much for your feedback. I'm setting up a couple of renders tonight with the IM samples at your suggestion. I'll post the results tomorrow.

Have a good one!
Hoop

[flipside]

"splotchy shadows"

Micha, don't you use QMC GI with that full adaptive mode??

I think your problem is mainly coming from your secondary GI engine.

Samples in ir map settings controls how much neighbouring samples are interpolated, so in fact it will simply blur your GI more, meaning lower shadow detail but less noticable splotches. Most important setting in ir map is the subdivs and min/max rate. For renders of about 640 to 800pixels wide, use -3/0 with 50 subdivs. If you double the resolution, lower the min/max both by 1 (1600pixels----> -4/-1, 3200pixels---->-5/-2, etc...)

So what is your secondary GI engine? Lightcache would be ideal for interiors.

If you can, post the scene and we can take a look at it.

[Micha_cg]

"splotchy shadows"

Micha, don't you use QMC GI with that full adaptive mode??
...

Please tell me more.

[Hoop]

some results

Hi Flipside,

I did a couple of renders last night with Micha's suggestions and it did correct the splotchy shadows eventually. It's hard for me to tell if it blurred the GI with this render since i don't have another to compare it with with this setup.



My secondary engine is Quasi Monte Carlo. this was the default and Vray didn't come with any manual so i wasn't sure what the others meant so I just stuck with that. My Min/max rate was -3/0 with 50 subdiv. And the pixel size was 527 x 331.

I'm going to try the settings you suggested, as well as change my secondary engine to Light Cache, and then i'll repost the results.

THANK YOU VERY MUCH for your help with this.
Hoop

[Hoop]

weird results

The first image is with IR map at -3/0 with 50 subdiv and secondary bounce as QMC. (same size at 527 x 331)

The second image is with Light Cache as the secondary bounce. The shadows look much better but the image color is VERY different. I'ts very red and looks horrible. Can anyone explain this?

Thanks, Hoop

[bdcali_cg]

"splotchy shadows"

What Color Mapping technique are you using?

[flipside]

"splotchy shadows"

Wow that's strange! Could be many things probably... Looks like an extreme colour bleed from the floor maybe. Try lowering your secondary GI multiplier, never use GI multipliers higher than 1! Also avoid very light materials or you can have infinite bouncing rays.

About the other images, sure you're talking about the samples and not the subdivs of your ir map?

If you can, post all of your settings of each rollout, or post the scene or a part of it. Or trough pm if you don't want to give access to everyone reading this forum.

[flipside]

"splotchy shadows"

Micha, don't you use QMC GI with that full adaptive mode??
...

Please tell me more.

Well, if you use the vlado universal settings stuff, the GI there is based on QMC GI i thought?

[Hoop]

settings

bdcali -- the only color mapping i'm doing is upping the dark multiplier after calculating the IRmap to tweak the image a little. Linear Multiply was the default. is this not correct to use with Light Cache? these images are straight out of Vray with no photoshop.

flipside -- here are all of my settings, most are at default. The only difference between the images in my previous post is that i used Light Cache as apposed to QMC for the secondary engine. The first image (non red one that used QMC as second bounce) looks very much like my materials in my material editor. So i'm very confused as to what is going on with the light cache image. And yes, the images with the samples settings (50, 128, 512) were the samples that i changed, not the subdivisions.



thanks again for the help.
Hoop

[Micha_cg]

"splotchy shadows"

Micha, don't you use QMC GI with that full adaptive mode??
...

Please tell me more.

Well, if you use the vlado universal settings stuff, the GI there is based on QMC GI i thought?

I'm not sure what you mean. Yes, I use Vlados method. I use it for all subdiv issues.

[flipside]

"splotchy shadows"

I simply mean that if you use 100 subdivs in your AA settings, this has no effect at all on your ir map subdivs. It does have an effect on your QMC GI subdivs though.

[flipside]

"splotchy shadows"

For your red image problem, try to set your secondary GI engine multiplier to 0.85. Also turn off 'store direct light' in your LC options.

In general, noise threshold of 0.002 is very low, I think you can get away with 0.01 and get similar quality. Surely for test rendering use higher values Unless you're testing the final image quality of course.

[Micha_cg]

"splotchy shadows"

Hoop, it looks not so bad. It's a typical indoor lighting in a warm orange room. You exterior light is much to less and the interior light to bright. You can set the blueish environment brighter or you place blueish arealights in the windows. I would do a test render without indoor lightting. If the light intensity of the outdoor lighting is good, than you could add the indoor lighting.

The secondary LC is a must for me. It helps to get the right lighting. But you must be careful, the brightes surfaces have a reflectance of 80% (brightest real world white). Often, textures are to bright for the physical correct rendering. A good allround multiply value seems to be 0.8 at the texure control. You should not forget - a bight real world white must be set grey (200,200,200) in your renderer.

I prefer the "reinhard" color mapping with burn 0.8 ... 0.5. It's something between expontial (burn 0) and linear (burn 1) color mapping.