[vray again] what causes the 'hotspots' where geometry meet?

[cgbeige]

The only thing that comes to mind is that you've increased the multiplier value for the bounces. Make sure it's at 1

[InfernalDarkness]

Without knowing much about your shaders or your lights, or your render settings, I'd try CGBeige's idea and also check the "Scale" on your FG bounces. This should be a value of 1.

Or are you using photons as well? You don't really need photons on this kind of scene... That said, you can increase both photon accuracy and FG accuracy on a per-object and per-shader basis. That may help clean up your chair, for example.

To give your table contact shadows, raise it a touch off the floor. If that doesn't help enough, use an Ambient Occlusion pass to create some nice contact shadows.

[Richard7666]

This is using Vray, not Mental Ray. I'll edit my post as I only mentioned vray in the title, sorry lol.

[thev]

Make sure you are not using perfectly white materials; no material in nature is perfectly white. Below is a table for the diffuse levels of some common materials (taken from http://spacemath.gsfc.nasa.gov/weekly/MMM1.pdf):

Snow 80%
White Concrete 78%
Bare Aluminum 74%
Vegetation 50%
Bare Soil 30%
Wood Shingle 17%
Water 5%
Black Asphalt 3%

Best regards,
Vlado

[Richard7666]

One thing I note though is that the hotspots 'invert' so to speak depending on whether the shelves have Soften Edge or Harden Edge increased. The model was imported as a .3ds so I did this to eliminate some bizarre-looking shading in the viewport.

Are the hotspots in the back corners of the sleves 'natural'? They are still visible even with this new material.

However the skirting board and walls are all native Maya and still have the issue. Even after I lowered the wall diffuse from pure white (note these are all vray mtl).

http://img818.imageshack.us/img818/1941/vraytestlounge4.jpg (http://img818.imageshack.us/i/vraytestlounge4.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

[cgbeige]

what's your scene scale like? Judging by the feel of it, it has that doll house tininess, which is why you might be seeing light feeling like it's amplified, since you're basically creating a scene that's an inch tall. Just a thought

[tharrell]

I'd also look at the scene scale, as well as your GI methods. From what I can see you're not getting much of any direct light on your first couple bounces and the scene is flattening out as a result.

Are you using sun/sky outdoors along with a rect light in portal mode for your windows? If so, make sure you're using physical cam exposure on your camera.

Using a portal in the window will allow you to focus your direct light into the room, and hopefully sharpen things up a bit. Make sure to turn up the subdivs on your portals.

What GI method are you using? If it's brute force/lightcache, I'd suggest taking the lightcache multiplier down to .9-.95 to take a bit of the glowiness out and hopefully get some of your contact shadows back.

Hope some of this helps,

--T

[Richard7666]

Yeah the whole room is smaller than the default grid. Only 15 units long.

I'm using irradience map + light cache. No portal lights (didn't know vray had them?)

Also I'm using Gamma Correction with a value of 2.2 and have 'treat as vray physical camera' enabled on the camera.

[Respawned]

For the jagged chrome try turning on "clamp" in the color management rollout (I think that's where it is, cant check at the moment), that usually works for me (in 3dsmax though).

[cgbeige]

I'd avoid the clamp if you're a V-Ray newbie since it will prevent you from learning how to get things in range with the Physical Camera node, instead it just hammers it back down in range for all renders. It's easy but it's not going to be good for learning and it can become a crutch IMO

it sounds like the scene scale is the culprit. That and the lack of the crucial part of a sun scene: "linear workflow" enabled. Your near-white materials are going to be over-bright without that on. Also, if you're using Blend materials with additive mode, those aren't energy conserving, so that can reflect more light than hits them.

But listen to Trey - he's the V-Ray lighting TD

[Respawned]

I'd avoid the clamp if you're a V-Ray newbie since it will prevent you from learning how to get things in range with the Physical Camera node, instead it just hammers it back down in range for all renders. It's easy but it's not going to be good for learning and it can become a crutch IMO

it sounds like the scene scale is the culprit. That and the lack of the crucial part of a sun scene: "linear workflow" enabled. Your near-white materials are going to be over-bright without that on. Also, if you're using Blend materials with additive mode, those aren't energy conserving, so that can reflect more light than hits them.

But listen to Trey - he's the V-Ray lighting TD

True, it can useful to see how out you are by selecting 'show clamped' but I agree it could become a crutch.

I would also listen to Vlado, after all he wrote Vray.

[Richard7666]

Here's a shot with 'Preetham et al' and default values for the Sun, color mapping set to 'Exponential', and a rendered through a maya standard camera. Definately an improvement.

http://img139.imageshack.us/img139/5931/vraylounge4preetham.jpg (http://img139.imageshack.us/i/vraylounge4preetham.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

Boosted scene scale and still a similar result. Room now measure about 1000 maya units, up from 15.

Regarding geometry, is it possibly because I have 'intersecting' geometry? For instance the skirting board actually intersects the wall. Having said that, the shelves don't intersect anything, even each other but they're still unnaturally bright in the inside corners. I don't really know the rules regarding vray and geometry. Everything aside from the chairs is fairly lo-res.

Also what would be a good Sun, colour mapping and camera set up? Starting from scratch basically I think...because I really don't have much of an idea what I'm doing. Should I bother with gamma correction (eg setting up gamma of .454 on my textures and setting Colour Mapping to Gamma Correction and 2.2).

thanks guys I'm learning a lot here!

[Richard7666]

aha! tweaked the Light Cache sample size to 0.02 down from 5 (far too high I have learnt) and voila!

Lovely contact shadows where before there were ugly light hotspots.

http://img259.imageshack.us/img259/1091/vraylounge4lightcache00.jpg (http://img259.imageshack.us/i/vraylounge4lightcache00.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

[tharrell]

Here's a shot with 'Preetham et al' and default values for the Sun, color mapping set to 'Exponential', and a rendered through a maya standard camera. Definately an improvement.

Boosted scene scale and still a similar result. Room now measure about 1000 maya units, up from 15.

Regarding geometry, is it possibly because I have 'intersecting' geometry? For instance the skirting board actually intersects the wall. Having said that, the shelves don't intersect anything, even each other but they're still unnaturally bright in the inside corners. I don't really know the rules regarding vray and geometry. Everything aside from the chairs is fairly lo-res.

Also what would be a good Sun, colour mapping and camera set up? Starting from scratch basically I think...because I really don't have much of an idea what I'm doing. Should I bother with gamma correction (eg setting up gamma of .454 on my textures and setting Colour Mapping to Gamma Correction and 2.2).

thanks guys I'm learning a lot here!

Looking way better now!

I would definitely use a gamma correct of .454 on all of your texture nodes that contribute color information (so diffuse, ref color etc). I also go as far as plugging a 1-stop ramp into a gamma then into color slots on materials and lights if I'm using a color swatch.

In general I'm a fan of using the following workflow in my color mapping globals (they work for me, other folks like checking linear workflow):

Type: linear multiply
Gamma: 1.0 (bright scenes) or 2.2 (dark scenes) to boost problem areas for adaptive sampling
If you have hotspots that are blowing out and difficult to antialias, enable clamp at around 6 + subpixel mapping, otherwise leave both off.
Don't affect colors (adaptation only): checked
Linear workflow: unchecked (big fan of being able to graph shaders and actually see what's going on. I favor Maya gamma nodes over the VRay gamma attrs on file nodes for the same reasons).

Portal lights in VRay are cake to set up... just use a vray rect light and check the box for skylight portal after placing them in your door/windows. You'll be able to turn the physical sun subdivs way down as a result.

I am noticing that your exposure is set for the sky outdoors, but you're getting highlights blowing out inside. Make sure that you're not using additive mode on any blend materials (as Dave mentioned), so you're conserving energy.

In general, if you're exposing for indoors, your sky should be slightly blown out if you're going for a true photographic look. There's lots of advice on how to treat that both in the epic "VRay-like interior renders" thread here, as well as some quite good info on the mental ray physical sun examples in the Maya docs (how to tune your exposure is pretty universal, and it has quite good info).

Also... when in conflict, take Vlado's advice over mine. I'm still a bit of a noob when it comes to VRay. :)

--T

[Richard7666]

thanks!

I take it I should be using Preetham et al as opposed to the CIE for the sun? The MR sun and sky help says they're not for 'visually pleasing images', I assume this applies to VRay too?

And I gather you just use the standard Maya camera?

Regarding the darkness, is there a 'preferred' way to counter that? I am currently experimenting with countering that by increasing the Sun's intensity multiplier, but portal lights are maybe a better option?

this http://vray.info/tutorials/vraydaylight/ looks promising, although it is an outdoor scene it seems to have good info on using physical camera, sun and sky, and tone mapping for a very nice result. Things go awry when they start talking 3dsmax language though :(

srgb button in the renderview? Does maya have an equivalent?

EDIT: glory! I have found the Vray frame buffer. This should make things easier!

[tharrell]

thanks!

I take it I should be using Preetham et al as opposed to the CIE for the sun? The MR sun and sky help says they're not for 'visually pleasing images', I assume this applies to VRay too?

And I gather you just use the standard Maya camera?

Regarding the darkness, is there a 'preferred' way to counter that? I am currently experimenting with countering that by increasing the Sun's intensity multiplier, but portal lights are maybe a better option?

this http://vray.info/tutorials/vraydaylight/ looks promising, although it is an outdoor scene it seems to have good info on using physical camera, sun and sky, and tone mapping for a very nice result. Things go awry when they start talking 3dsmax language though :(

srgb button in the renderview? Does maya have an equivalent?

EDIT: glory! I have found the Vray frame buffer. This should make things easier!

Well, for Prietham/CIE etc... in my opinion it really depends what it is that you're shooting for. I prefer Prietham when I'm actually seeing the sky in my renders. Latest project... CIE overcast wins. It's up to your eye, really.

I *almost* always use physical cam if I'm cranking my brights super super hot or using physical sun. Unless it looks cool :twisted:

The difference between Max and Maya (well, MR MIA) language is extremely slight when it comes to VRay. Learning to know what you're shooting for (exposure/contrast/mood/beauty) is way more important. Don't let the tech get in your way.

And yeah, the buffer is a godsend if you're in 2011+


--T

[InfernalDarkness]

Learning to know what you're shooting for (exposure/contrast/mood/beauty) is way more important. Don't let the tech get in your way.

Most inspirational statement ever. Thanks for sharing! As fundamental as it should seem, very well-phrased and implicite... I needed to read that!

[cgbeige]

And yeah, the buffer is a godsend if you're in 2011+


--T

RT in the 2.0 nightlies is an amazing help too. CPU-only for now but I'm not complaining.

[Hamburger]

Hey guys, I'm late to the party but there is actually a slight difference the way V-Ray handles standard Maya mats compared to it's own vraymat shader.

Like mental ray, this scene will probably work better if you convert them all to vraymat shaders as GI is seems to be more optimized. I'm hoping Vlado won't correct me here though but through my own scenes that were freshly imported with phong mats, the vraymats performed much better...less noise, less GI artifacts.

[cgbeige]

ya, I've noticed that as well.

[dangerweenie]

Hey,

i don't really see any hotspots, but off the top of my head i know that "check sample visibility" as well as the "normal threshold" "color threshold" and (i think this is the third one ...) "distance threshold" all affect how GI behaves around areas where geometry is close to geometry.

with Vray. See for instance in this image, where the skirting board meets the wall, and where the shelves and cupboard doors meet. Also, does the coffee table appear to not be as grounded as it should be? And what would be causing the jaggies on the chrome at the top of the chair backs?

http://img841.imageshack.us/img841/3924/vraylounge1.jpg (http://img841.imageshack.us/i/vraylounge1.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.