blotches - too MUCH info to make sense of it all :) Help?

[ripe]

Hi. Still getting used to vray, loving it, but still struggling a little bit

There's loads of info on getting rid of blotches in your renders, but I can find hardly any with pics to back up the huge amounts of text describing how to fix the issue. So, I'd really appreciate it if one or two of you guys could take a look at my renders and my settings and let me know how I might fix/get rid of the blotches? Render time is quite an issue here - we need to get these renders out ASAP. Of course, if I need to take a long time to render them very nicely I will

Anyway, each of these renders is 3000px wide originally, so very high res, and when I play with them in photoshop to adjust contrast, levels etc, the blotches just become more evident...











So there you go - I think maybe the answer is that my QMC sampler is set too high in the noise threshold? But if any of you lot could have a look at the settings that would be very much appreciated.

Thanks

[nlo]

just a guess:
i thinks that might be a noise coming from vray-lights.
set vray light subdivs to maybe 25...

[deadpencil]

It could be the area light samples - if you're using an area light...but I'd expect the noise to look a little different.

My suggestion would be:

On your irradiance map, try a setting of
HSph. subdivs = 100
and
Interp. samples = 40

See if this cleans it up any.

On a side note. I've never used a diffuse bounce multiplier of a smaller value than the secondary bounces multiplier. Could this have anything to do with the pronounced noise effect?

[ripe]

Cool, I'll deffinitely try both those tips mentioned above. Do you know what effect it'll roughly have on render times? Only roughly, i know it's very difficult ot guess. The images took about 3.5 hours each on a dual Xeon 3GHz system. Would the time double or more with the suggested settings d'you think?

The thing is, my settings worked fine on the small scale test renders I did at 640 x 480 resolution, so I figured I just needed to up the resolution and it'd all be OK? The test renders we're perfectly smooth.

Is it generally good practice to increase the HSph. subdivs and vray light subdivs when image size is greatly increased?

Any more tips for getting rid of blotches would be great too!

Or, does anyone know of any post processing that can be done in photoshop to help smooth it out? I just tried using the Smart Blur with no luck

[deadpencil]

3.5 hrs seems like a long time for that scene since it doesn't look very complex. I think that with 3.5 hrs rendering time you should have a near perfect GI solution (no artifacts).

One other thing I've noticed is that you have the Direct computation (under secondary bounces) subdivs and depth set very high. Try a setting of 5 for both and you should notice a decrease in rendertime.

If it is the vray light samples causing the artifacts, the shadow samples (or subdivs - can't remember what it's called now) only need to be set relative to the size of the area light. So if you have a small area light then a smaller value is required. Try a setting of 8 to start you off, 25 sounds a bit high.

[sv]

bring down your QMC samples to around 20, and you could take down your secondary bounces - 15 is well high and will be giving really long renders. Increase the subdivisions on your vray lights to get rid of the bloches. this will increase render times but by lowering your secondary bounces you should get around this.

[ripe]

Right, decreased the QMC samples to 20, increased the HSph. subdivs and the Interp. samples too. I've set if off, we'll see how long it takes...

I am not actually using any vray lights in the scene. I've used the Photometric MAX lights with an IES file to get the pattern. I've got the shadows for these set to VRay shadows - I've just upped the samples for these shadows from 8 to 18. Is this the same as upping the VRay light samples, or is there another way of getting more samples from the IES lights?

[egz]

The blotches in your image are typical for too low Hsphere subdiv settings. Increasing this should fix it (like everyone else already mentioned )

[sv]

remember to drop the subdivisions on your secondary bounces - in my experience 15 is very high, and will take a long time to render. To get the times down, also try rendering out the IR map at double the quality but half the size, and rendering from this saved file.

[robing]

My humble advice....


Secondary bounces Mult: please set it to the default value>>> 0.5 and play with the color maping instead. value over 0.5 will increase render time...

HSph. Sub : 50 is too low, set it 80/100 and play with inter. samples for smoothing the irr map.

Direct comp subdivision : 15 is a very high setting, good for very detailed scene with a lot of small objects, in this scene a value of 3/5 is a better choise

Direct comp Deph : for interior 15 is a minimum, remember in the real life the bounces are infinite (with a inverse square decay of course), so start to test with 20/25 settings.

check Sample visibility : Don't need it in your scene, take a try without it will give you better render times.

QCM min samples : 100 is a very very very high setting, my experience said>>>> don't touch it and use the default value, and if you need some improvement increase tis value very slowly.

Hope this can help you

PS: excuse my bad english

[Gijs]

I think your irr map settings are too high . You mentioned your rendering originally is 3000 pixels wide
-3 -1 is for screen resolution a good setting. Try the high setting and customize -3 0 to -5 -2 or even -6 -3 and I am quite sure the quality goes up and your render time goes way down.

You already mentioned that on 640 x 480 it looked right. If you then up your resolution about 5 times, and leave the irradiance setting at -3 -1, you get a splotchy end result.

[ripe]

OK, all good advice for which I'm very grateful But, if I lower the seconndary bounces multiplier, depth and subdivs, won't it make the scene much darker? I already have my Colour Mapping set to 1.9 in the dark multiplier with HSV exponential? Is there another way of getting the light to bounce further into the scene?

[robing]

set the first bounce to 1.00 it will light up the overall scene, set the secondary bounce to 0.5, it will give you more contrast and shorter render times, don't lower the deph, instead give it higher value 20, 30 even more...(the QMC sampler works for you)
and if your scene is dark... take a look at the lights settings, there's something wrong with it.
and remember in the real life you can't light up a entire room with a single 60w luminaire.
.... and every time I can , i try to use LINEAR color mapping, some time I can't , so i use exponential and make a big cooking in photoshop, because expo. method washout the contrast and the lights dynamic, don't realy like it..
You can also give to the ceiling a vray wrapper material and set the Generate GI to 1.2/1.5.

...and I see your walls are yellowish (are they originaly white?) , try to add a Wrapper to you floor mat and lower the Generate value 0.8/0.7 it will reduce the Color Bleeding, and contribute to a good contrast.

[Frances]

Wow. I just feel like I had a whirlwind trip through VRay University! I am constantly amazed at the wealth of information that is shared here.

Well, back to the subject. I think if the scene is lit only by spotlights, it won't be much brighter without looking unrealistic. From my experience, spotlights are "stubborn" about giving up interdiffuse lighting.