[JDHill]

Sure, http://www.rapidshare.de

[mverta]

Yes, first of all your scene scale is off or your camera settings unrealistic. Make sure your scene scale is 1:1, and tell me your camera focal length.

Second, I'd assign a white lambert to the whole thing and just debug the lighting using an ISO of 400, with f-stop 4.0 and ss around 125, but might have to be much lower.

Start there and I'll guide you through the rest.

_Mike

[lsega77]

Sure, http://www.rapidshare.de

Thanks, JD. Hopefully I did this right

http://rapidshare.de/files/15699876/18C ... c.rar.html

I have a .3ds, .obj and a max 8 version in this .rar file.

You'll notice that the model is two peices a 'shell' and the 'cells.' What was cool about the maxwell version of this light is I set up a 1'10" x 3'10" (emitter) plane inside the 'shell' just above the 'cells' inside the fixture as opposed to the vray light plane which was just a few inches below the 'cells' (if you can wrap your head around that one. Looking forward to using those light preset for luminaire setups like this

Just apply the m_aluminum mat from the basic vol i folder.

hope it proves useful to you guys

[lsega77]

Yes, first of all your scene scale is off or your camera settings unrealistic. Make sure your scene scale is 1:1, and tell me your camera focal length.

Second, I'd assign a white lambert to the whole thing and just debug the lighting using an ISO of 400, with f-stop 4.0 and ss around 125, but might have to be much lower.

Start there and I'll guide you through the rest.

_Mike

Thanks Mike that would be awesome. I'll cook it again with white lambert and repost.

Here's a snap of my cam settings. Oh and scene scale is set to 1.000.



That focal length came from my creating a maxwell camera in max using the same positioning of the standard camera I used for the vray render.

[lsega77]

[EDIT]Moved to first post

[JDHill]

Sorry lsega77, I have been quite busy today, and haven't had a chance yet to inspect your scene, but try changing:

F-Stop: 8
ISO: 100
SS: 125

...and go from there...I'll take a look as soon as I can.

~JD

[lsega77]

Sorry lsega77, I have been quite busy today, and haven't had a chance yet to inspect your scene, but try changing:

F-Stop: 8
ISO: 100
SS: 125

...and go from there...I'll take a look as soon as I can.

~JD

No prob JD. I appreciate the time your taking to help out when you can. I'll try your changes.

BTW. This is just a scene I'm using to learn and get a handle on maxwell render, so I'm not in a time crunch to get it done. Figure it would be a good case study for me to learn with.

[mverta]

Also, do me a favor and drop the roughness from Lambertian to 99.

_Mike

[lsega77]

Also, do me a favor and drop the roughness from Lambertian to 99.

_Mike

will do, I'll repost tomorrow.

[lsega77]

Ok so here's the revised render with:
F-stop: 8
iso: 100
SS: 125
white-mat (roughness 99)

[Edit]Removed image as per MV suggestion

With this image I don't understand why it seems that the edges are darker and the middle so overbright. I know my lights are somewhat away from the wall but I don't think that light attenuate that drastically along the sides (if that makes sense).

I'm going to reduce my light intensity and renrender (btw all these renders are 5hour cooks). I'll keep f-stop, ss and iso the way they are though.

[jdp]

I think this is the famous vignetting effect, though I am not sure. if so it has nothing to do with the light intensity but with optical lens distorsion, check this out:

http://www.maxwellrender.com/forum/view ... vignetting

[mverta]

Ok, couple of things:

You don't have to publish blown-out renders. If your scene is rendering bright, at least for the time being, adjust the ISO in MXCL so the exposure is at least correct. We're trying to judge the relative light propogation right now, not absolute exposure. If you're watching the render and you can see it's too bright, then I'd suggest increasing the shutterspeed until it's just shy of being overexposed.

Also, what do your emitters look like, geometry-wise? I'd also recommend pulling the light fixture diffusers out for a few tests. We just want to see straight emitters and shading.

This looks like one of those scenes that will be better to test with a more real-world reflectance like 200,200,200 instead of pure white, which basically doesn't exist. Sometimes that's more useful, but it doesn't appear so in this case.

I also would like to know if your scene is completely enclosed, i.e. has all 4 walls.

You don' have to let this render for 5 hours to check, I bet you can get a decent idea in an hour, or perhaps reduce the size just for the tests.

Thanks,

_Mike

[lsega77]

Ok, couple of things:

You don't have to publish blown-out renders. If your scene is rendering bright, at least for the time being, adjust the ISO in MXCL so the exposure is at least correct. We're trying to judge the relative light propogation right now, not absolute exposure. If you're watching the render and you can see it's too bright, then I'd suggest increasing the shutterspeed until it's just shy of being overexposed.

Also, what do your emitters look like, geometry-wise? I'd also recommend pulling the light fixture diffusers out for a few tests. We just want to see straight emitters and shading.

This looks like one of those scenes that will be better to test with a more real-world reflectance like 200,200,200 instead of pure white, which basically doesn't exist. Sometimes that's more useful, but it doesn't appear so in this case.

I also would like to know if your scene is completely enclosed, i.e. has all 4 walls.

You don' have to let this render for 5 hours to check, I bet you can get a decent idea in an hour, or perhaps reduce the size just for the tests.

Thanks,

_Mike

The emitters are just simple planes, normals down, 1x1 segments.

The scene is completely enclosed except for the two window you see in the background (full walls behind camera).

I'll adjust the mat and rerender for about an 1hr-ish or so.

BTW, should I leave the intensity of the emitters at 7200 or should I reduce and work my way up/down from there?

Thanks Mike.

[mverta]

It's been awhile since I worked with RC5 emitter values... I'd say you can lower them a touch, but it won't really matter for this first set of tests.

_Mike

[Hugh]

With this image I don't understand why it seems that the edges are darker and the middle so overbright. I know my lights are somewhat away from the wall but I don't think that light attenuate that drastically along the sides (if that makes sense).

The illuminance in the centre of the room has a contribution from all the lights in the room (depending on the cut of angle of the louvre), so will always be brighter. The edge have far fewer luminaires contributing to the light level at any one point so to compensate, the space between the wall and the centreline of the first fitting should be no more than half the general centre to centre spacing across the room. In this case the effect is amplified by the grouping of luminaires toward the centre of the room.

The way the vray render was set up (invisible area light below louvre) will give you a light distribution more akin to a light fitting with an opal diffuser, a very wide distribution. Which is why the light cutoff is so high on the walls. A specular (read mirror finish) louvre, in general has a much narrower distribtion and will give you something much more like the maxwell images in reality.

What I'm saying is that the maxwell light distribution is more realistic given the geometry of the light. If you want the lighting to look like the vray one, you can do one of the following:

1. fake it with invisible area lights (seen that you can do this somewhere if you hide emmiters in studio)

2. Change the lighting layout (closer to walls, more evenly spaced)

3. Change the light fitting to something with a much wider distribution. Which would be fine IMHO unless the space has lots of VDU's in it.