2009 Rendering Lighting Problem.

[Graeme Padgham]

Has anyone managed to render an internal scene using both artificial & sunlight settings.
The renderer has the options of 'Artificial Only', 'Sunlight and Artificial', or 'sunlight only'.

When choosing sunlight and artificial (so i can see nice sunlight coming through my windows), it doesnt render with the artificial lights on (ie. it renders identical to the 'Sunlight only' option) so its pitch black inside and you just see some windows with light coming through.

Stumped.!!

[jeffh]

Try makign modifications to the exposure after the render is complete. That might help with the issue.

[etboards17]

Have you checked that all lights are on?

[Mike Sealander]

We have also had a lot of trouble with sunlight on in an internal rendering. Exposure adjustment does help, but it still seems something fishy is going on.

[t1.shep]

Are you using light families from and older version of Revit? That could be one issue although I can't verify it. I would also make sure that you have the appropriate lights turned on in the scene and then also check to make sure that the lights aren't obscured by something and that they are being hosted correctly and not inside a wall or ceiling.
I've done an interior rendering with a wall sconce and studio lights and it came out just fine.
The other thing to check is that with the new MentalRay, your lights behave in a physical/photometric manner, so making sure that their settings are correct. Check the "light loss factor" and "Initial intensity" settings.
Hope you get it to work.

I also just read this in the Autodesk "hot issues" release...
http://usa.autodesk.com/adsk/servlet/ps/item?siteID=123112&id=11226810&linkID=9243099

[t1.shep]

We have also had a lot of trouble with sunlight on in an internal rendering. Exposure adjustment does help, but it still seems something fishy is going on.
I've noticed that when rendering an interior scene and wanting to have light come through windows you need to go in and make a custom rendering setting and make sure that the "daylight portal options" boxes are check for windows or doors.
I think that you can get an interior scene to render without it, but I'm guessing that it will look better if they are used.

[Graeme Padgham]

Answer to above, yes i have checked all lights are on.

I have tried a custom render setting with daylight portals but still no joy.

I simplified the test by creating a square room, with 1 window, 1 light (from revit library).
rendered fine interior only artificial only (but black windows)
switched it to sunlight only, rendered as expected (dark inside apart from sunlight through window).

Switched it to Sunlight and artificial, and still the same as sunlight only. so no interior lights.

I have attached the file if anyone can have a look to see if they can render it with sunlight and interior light..

Im going bananas..
Thanks
Graeme

[still.james]

i had a mess and changed the exposure level to 4 from 12.

see image

doesnt look right though :S

[iru69]

It's broken.

http://forums.augi.com/showthread.php?t=80236
http://forums.augi.com/showthread.php?t=80126

There have been a couple work-arounds suggested.

[t1.shep]

I did one rendering with the settings that you had, plus some tweaks to the exposure settings (lighting issue 1).
I did another rendering adjusting the light fixture's properties to be a 100W light instead of the 60W or whatever it was (lighting issue2).
Both times the default exposure settings were too dark. I just adjusted the exposure to lighten the image and tweaked some of the other settings in the adjust exposure setting.
I seem to be getting light from both sources.

[sfaust]

it's not broken, it's realistic

[dfriesen]

it's not broken, it's realistic
;)
Ok then, it's the exposure that's broken, because I know for sure that in real life, when in a sunlit room, you turn on some lights, it does not suddenly get dark.

[hand471037]

It's broken.

Exposure control is a vital part of using Mental Ray. So it's not really that it's broken per say, it's that those folks coming from bone-simple Accurender don't yet know how to use Mental Ray.

It's the same if you're using Max. Although in Max you've got more options, and different types of Exposure Control, so it's easy to get good results with 'default' settings. It was one of the first things I ran into when I started teaching myself Mental Ray in Max.

You'll want to as part of your rendering workflow first to a draft or low quality rendering, set the exposure to what looks good, and then go onto your final rendering.

[Mike Sealander]

OK, this thread is getting wacky. What about using a rendering to see whether lighting levels are good? I'm not really interested in whether a digital camera might be able to use an exposure setting to snap a good-looking picture in a poorly lit room. I'm interested in knowing whether lighting levels are good for the human eye. The human eye knows what 20 footcandles on a painted white wall looks like.

[jeffh]

OK, this thread is getting wacky. What about using a rendering to see whether lighting levels are good? I'm not really interested in whether a digital camera might be able to use an exposure setting to snap a good-looking picture in a poorly lit room. I'm interested in knowing whether lighting levels are good for the human eye. The human eye knows what 20 footcandles on a painted white wall looks like.

Hence some of the problems discussed here. I am by no means a rendering expert but I can tell you that the human eye is a far more sophicticated light gathering insturment than even the most advanced camera. A human eye is CONSTANTLY adjusting to light levels and has a MUCH larger dynamic range than any camera. The ability of cameras and renderings to capture this kind of range is limited.

[Graeme Padgham]

Thanks for all above help (didnt want to cause a war!!)

I have played around with the exposure settings and it appears to be getting better, i think the comment above is correct on not knowing the mental ray renderer enough.

But i still cant work out why a scene would get darker by simply adding MORE light (sunlight) into it.

In simple terms, i created a perfectly lit interior scene (with NO sunlight), when i put the sunlight on to get realistic bright windows it all went wrong, is this really a mental ray renderer thing?

Thanks

[hand471037]

In simple terms, i created a perfectly lit interior scene (with NO sunlight), when i put the sunlight on to get realistic bright windows it all went wrong, is this really a mental ray renderer thing?

Yes.

In Max, when you're using a certain type of semi-automatic exposure control, it's related to the sun. If you've got a daylighting system (i.e. sun) in your model, or turned on, it changes the exposure automatically to compensate. Otherwise you'd get a solid white picture when you render.

So when you're turning the sun on for your render it's effecting the Exposure control defaults, which is then making your scene look darker.

As for the 'I just want to know if the lighting scheme works or not' what you're talking about is what's commonly called a 'false color' or 'pseudo color' rendering. This is a rendering that just shows you the amount of lumens on various surfaces by painting them with a color that corrisponds to a lumen range. Radiance, Mental ray in Max, Ecotect, and IES (I think) can make such images, Revit can't at this time.

So think of it like this. Rendering in Revit with Mental Ray will let you know if you're close to what you want, but you'll need to use an actual analysis tool that gives you real numbers if you want actual 'proof' (i.e. hard numbers) that your scheme works.

[iru69]

I hear what you're saying... it's not like I want it to be broken.

However, this isn't even about getting "good results" with the 'default' settings. This is about getting a completely black image with the 'default' setting. Okay, so I'm willing to ring that up as just some sloppy work by the Factory. But then I start adjusting exposure settings, a little bit of this, a little bit of that, test render after test render after test render... and 'Interior: Sun and Artificial' never comes close to matching 'Interior: Artificial'. It's overexposed, it's underexposed, there are sparkles of white, there are clouds of white - bottom line is they're unusable images. And just like what others here have expressed, we keep thinking we're getting closer, but it's never quite right.

As I demonstrated in another thread (that I linked to in a previous post below), you can have zero openings, and simply by selecting 'Interior: Sun and Artificial', a rendering goes from normal to a screen of black. Even with a single window, the same results.

Whether the design of the feature was intentional or not, if it's impractical (impossible?) to get the intended results, I call that broken... of course, you folks are all free to call if whatever you want.


Exposure control is a vital part of using Mental Ray. So it's not really that it's broken per say, it's that those folks coming from bone-simple Accurender don't yet know how to use Mental Ray...

[mruehr]

Since i had a job with a professional photographer in my youth
when photographing a hotel lobby we always made 2 pictures
one with the right settings for the interior light and one for the exterior light
they got overlaid later.
rendering software needs to have a different mathematical model
for different lighting conditions to calculate the right lighting impression for the
2d world
as far as i can see it works right.
even when there is no window you change the type you change the mathematical model

[iru69]

Since i had a job with a professional photographer in my youth
when photographing a hotel lobby we always made 2 pictures
one with the right settings for the interior light and one for the exterior light
they got overlaid later.
So I take from that little anecdote that we need to render two images and merge them together to get the intended image. That sounds like a work-around for a broken process.

rendering software needs to have a different mathematical model
for different lighting conditions to calculate the right lighting impression for the
2d world
I'm sure it does need a different model. The mathematical model they used appears to be broken.

as far as i can see it works right.
Well, if you think that dark underexposed images and photoshop workarounds are "works right", you're entitled to that opinion.

even when there is no window you change the type you change the mathematical model
I'm sure it does change the mathematical model. The mathematical model they used appears to be broken.

Okay, I'm done with this here... this is moving into the surreal stage. When people start defending Revit in the face of all evidence to the contrary, it moves into 'Revit Apologist' territory. And there's no point in discussing something with the Apologists.

p.s. and if someone does figure out the "magic" settings, or actually has a tutorial on how each exposure setting affects the image, please post.

[t1.shep]

Here's a thought...Someone post a Revit file that they're not getting the image they like when rendered, and post that image as well. An accurate description of what you don't like or issues about the image would help too, as I'm not fully understanding the issue. If you want a nice image, I think revit and some tweaking works pretty well. If you want spot on accuracy with this many lumens with this amount of fall off with this much sunlight coming through this size opening at this time of day with this % cloud cover...I wouldn't know where to begin.
Then let some of us take a crack at it to see if there really is no way to get the image to an acceptable standard.
I was working on some renderings a few weeks ago and many forums and webpages and tutorials that I came across, some from highly skilled graphic artists, said that they rarely get a final rendering straight from the original program that it was rendered in. Most said they they will do some sort of post-processing in another program (typically photoshop.)
I'm most interested to see what the problem is since we're all pretty new to MR in Revit. Most quick renderings that I've done I've been happy with. I want to see if I'm missing something here that's going to come around and bite me in the rear.
As for complex lighting situations (interior lights and exterior lights, evening sun with strong highlights and deep shadows), that's what HDR images are for. I don't think that Revit can handle those at the moment, but I know Max can.

[Mike Sealander]

OK, this is what's broken:
The help file!
Sure would be nice to have documentation that did a little explaining.

[hand471037]

However, this isn't even about getting "good results" with the 'default' settings. This is about getting a completely black image with the 'default' setting. Okay, so I'm willing to ring that up as just some sloppy work by the Factory. But then I start adjusting exposure settings, a little bit of this, a little bit of that, test render after test render after test render... and 'Interior: Sun and Artificial' never comes close to matching 'Interior: Artificial'. It's overexposed, it's underexposed, there are sparkles of white, there are clouds of white - bottom line is they're unusable images. And just like what others here have expressed, we keep thinking we're getting closer, but it's never quite right.

Welcome to Mental Ray. Now you see why all those folks that use Max talk about how it's hard to use, and instead like vRay or Maxwell. It's gotten easier to use in Max these days, but it's still not the easiest thing to use ala Accurender. I think that Autodesk actually has done a pretty good job at 'boiling down' Mental Ray to work with Revit. If you've ever worked with the 'full' Mental Ray, especially prior to the 2008 version of Max, then you'll very much know what I mean.


Whether the design of the feature was intentional or not, if it's impractical (impossible?) to get the intended results, I call that broken... of course, you folks are all free to call if whatever you want.

You know, you can blame Autodesk for all your troubles, or you can try to learn how to use the tools available. I, for one, am getting really really tired of all your complaining. You used to not be so bitter and angry, and I looked forward to talking with you about things and getting and giving help on using Revit. Here you're going off about how Autodesk 'broke' Mental Ray, when it very much sounds to me like you simply don't know enough about it yet.

[iru69]

Uhh, I know you sometimes sort of "get going" in that way that you do, so for the most part, I'm letting it slide. However, if you review all of my posts in the three threads related to this issue, there are no rants at Autodesk or the Factory or conspiracy theories, or accusations of how badly they screwed this up, etc. I've couched many of my comments with an openness to having someone explain how it works. So far, the explanations of "how it works" equals "broken" to me. Maybe a case can be made that I've been overly persistent in my conclusion, but it's difficult not to be a bit bewildered when certain people keep insisting that it's "user error" in the face of all evidence pointing to the software being the problem.

I don't want to go way off topic, so this is too be continued in a future thread... one that will really give you something to complain about...


You know, you can blame Autodesk for all your troubles, or you can try to learn how to use the tools available. I, for one, am getting really really tired of all your complaining. You used to not be so bitter and angry, and I looked forward to talking with you about things and getting and giving help on using Revit. Here you're going off about how Autodesk 'broke' Mental Ray, when it very much sounds to me like you simply don't know enough about it yet.

[iru69]

t1.shep, that's a great idea. I've posted the project file and images of the extremely simple test I posted in another thread. The project file was created in 2009 using OOTB components.

I rendered it using the default settings for 'Interior: Artificial Only' and 'Interior: Sun + Artificial', both at best quality (though I edited the setting to include windows). I then adjusted settings on 'Interior: Sun + Artificial' until I gave up: the third image (the exposure value is set to around 5).

The lighting level is still different, but acceptable. But I can't figure out how to get rid of the white refractive clouds. This is the same problem we're experiencing with many of our renderings where we adjust the exposure setting in order to equal the lighting level of the 'Artificial Only' setting.

Simply using the Revit rendering dialog settings, can anyone reproduce the light levels of the 'Interior: Artificial Only' image using 'Interior: Sun + Artificial' scheme without any artifacts (e.g. white refractive clouds)?

If someone is just going to come back with something along the lines of "that's the way real photography works", then we've got an irreconcilable difference of opinion on what "broken" means. If someone comes back with a reproducible solution, then hot dog, the beer's on me. :beer:


Here's a thought...Someone post a Revit file that they're not getting the image they like when rendered, and post that image as well. An accurate description of what you don't like or issues about the image would help too, as I'm not fully understanding the issue.

[ws]

Weird that...

you're right I'd say - it doesn't seem to work correctly with sun and artificial - I've tried all ways to improve it and end up with exactly the same results as you have done (not surprising I guess).

[rmejia]

An auto exposure button would be nice, and I do not think it would be that hard to do.

I too have gotten strange artifacts when using the Interior: Sun + Artificial combo (those unwanted circles). I have also gotten other artifacts, black areas in the rendering. To me it is a Mental Ray problem. These things (artifacts, blochy & splochy noise) also happen in 3ds Max with Mental Ray, which is one of the reasons I switched to VRay. VRay also has it's problems, but I know how to fix them and there is a lot of support in the VRay forums.

[Calvn_Swing]

Guys, guys...

I'm split down the middle on this one. While I can see Jeffrey's point on this one, (learning the render engine better, etc...) the fact is that Autodesk didn't give us enough controls in Revit to get decent images in the situation iru69 is showing. I also find that, no matter the tweaking, you can't get this to work in situations where you've got one single tiny window and a lot of artificial light. I also find that when you've got a low light exterior (say sunset or sunrise) you also have major problems getting it to work. Someone else nailed it on the head with the HDR comment. We really need Mental Ray in Revit to support HDR for a whole variety or reasons, this is just one.

Also, there is one major flaw in how Mental Ray is implemented in Revit, or how rendering is implemented I should say. I can only speak for myself, but when I render a scene I'm not looking for what it would look like to a camera. Max and mental ray were originally designed for cinema and gaming, the former explicitly trying to mimic a camera and the latter doing similarly because we're looking at them on a 2D screen. What I want when I render I want to see what it would look like if I were standing in that space in person. Period. So, fundamentally, we need a renderer that tries to approximate the function of the human eye, including adjusting to the exposure more automatically and handling HDR lighting.

All that being said, I think MR is a huge jump over Accurender in functionality and integration with Revit, and I really appreciate the work. I still agree that the way it is used in Revit is fundamentally flawed and needs to be fixed, and this particular issue is just a symptom of that flaw.

[t1.shep]

After playing around for a bit, these are the best that I could come up with. I'm definitely not satisfied with the results.
I changed the wall materials to just painted surfaces (one was a light green olive matte and one was light red matte).
while the light spots are not showing up, the color of the walls don't come close to the color of the paint material.
Also, these renderings were only region rendered and the rendering time for such a simple model was not acceptable in my opinion... 749 x 675 pixels at screen resolution and the renderings took over 5 hours. That's way too long just to get the spots to go away.
Here are the settings I was using for the test 2.jpg...

test 2
image precision 6
max reflection 8
max refraction 5
blurred reflections 8
blurred refractions 3
enabled soft shadows
soft shadow precision 8
compute indirect and sky illumination checked
indirect illumination precision 8
indirect illumination smoothness 8
indirect illumination bounces 4
daylights on.
wall material (light olive green matte paint)

sky: cloudy
about mid point on haze

exposure 9.95
hightlights .25
mid 1.1179
shadows .4315
white point 6500
saturation 2

So, ya, while I like the look of MR better than Accurender, I'd say there is some work, or a lot more learning to do within Revit.

[mthurnauer]

The comments that keep referring to the notion of 'What it looks to the eye' need to understand that is subjective. It is why a rendering is still artistic and not scientific. Here is an example: How bright does it seem outside when you first leave a movie theater? How dark is it in your house when you first turn off the lights verses after sitting in the dark for ten minutes? We adjust our interpretation of our environment which is why the post-process exposure correction is an essential step. You need to have the image of illuminance to be able to see the light level in a non-subjective way. What I bet you will find if you compare the light level of a room with artificial and natural light vs with natural only is that the illuminance is hardly different. I have looked at the settings of the exposure correction and what seems to be missing is that you should be able to set the footcandle range. For example, anything over 1000 footcandles is white and anything below 1fc is black.

[hand471037]

So it appears from doing some quick experiments with the 30 day demo of Max Design 2009 that Revit uses what's called in Max the 'MR Photometric' exposure control with a manually set exposure level. So, in other words, it's not 'pretending' to be a camera, but it is doing a lot of things with the exposure control that might not be intuitive or obvious.

This also ties into some of the other issues folks have been complaining about. For example, with the MR Photometric exposure in Max, you can't use a background picture when using a MR sky. Just like in Revit. You can only use a haze map to simulate clouds. So it appears that in RAC 2009 we're given a standard MR Sun and Sky system with the default settings therein.

Max actually has five different modes for exposure. These different modes tie into different effects and options that are available when you render, and within Max until you learn what modes do what, and allow for what, you'll drive yourself crazy trying to understand what's going on.

Also it has several different options for Sun and Sky, as well as full control over all aspects of the settings of each.

So in RAC 2009 we're limited to a single preset Exposure mode, and a single kind of preset Sun and Sky, and that's what is in turn limiting some of what we can do. Hopefully in the future more Exposure modes will be possible, such as false Color and Logrythmic, two that I've used in the past. Or the ability to 'fake' the sun into unrealistic but better-looking light levels.

Another thing is that it appears that the 'portal' option really just turns on what in Max are called Photons for the Windows, Doors, or Curtain Walls. Sadly, we don't have the ability to fine-tune those Photos in Revit like we do in Max at this time. This is the 'halos' you're complaining about, it's the photos on the wall not blending together nicely. We're given a some settings for this under the 'custom' settings, and by turning up the Indirect Illumination Precision and Indirect Illumination Smoothness we can get those Photons to blend together better. However, this also makes the renderings take a lot longer, for we don't have the nice Photon control to 'tune' the render for performance.

So if we know what these limitations are, and how to work with them, we can still generate decent renderings out of Revit. It is more limited than Max, but honestly, I'm more than OK with that. For without taking a deep dive into Max, you can't easily get even decent results with Mental Ray in a timely fashion. It's been dumbed down some for Revit, yes, but I don't think it was done as some part of a grand con on Autodesk's part to get us to buy Max, unlike many here.

While Autodesk is a big company, I honestly don't think that the Revit developers are evil. They might have missed the mark a little with this, or just not had the time to do everything they wanted to with this release, or implemented this in a way that some find problematic; but that's a very different issue than the constant negative tone here.

[zulu5d]

Apart from being an architect I come from an animation and render background, I only mention this is that you need to go over to softimage.com and see how mental ray is properly implemented. Its been the native renderer in XSI and Softimage 3D since the nineties and the results with their render tree is sensational..

[iankids]

I will preface what I want to say by acknowledging that I am a total novice at rendering.

Nevertheless, I have been following this thread with interest - partly in the hope of trying to glean some knowledge, but also simply for interest sake.

For a while prior to the release of Revit 2009 all of the hype coming from Autodesk or the Beta tester was ...........***Mental Ray is coming***........hold on to your hats.

Whist it is universally seen to be significantly better than accurender, it is obviously no where near other rendering mediums. Kerkythea - softimage - 3dmax etc.

In part, notwithstanding the renderings done by IRU69 (which, by the way I think are terrible images & if this is the best that an obviously competent individual can achieve, then heaven help me). I think, however, that its a case of over promising and under delivering. Had Autodesk not made such a big deal out of Mental Ray, my guess is that mostly we would be very happy for a better render engine than we had previously.

But having made the promise, it is my view that they should deliver on it & provide either a rendering system which can cope with the sort of situations described and shown in this thread, or provide us with a facility to export to a third party such as Kerkythea.

Cheers,

Ian

[ws]

that's a great explanation Jeffery - many thanks.

FWIW I think for external renders the way Mental Ray in RAC 2009 works is incredible, and internal renders seem OK with just sunlight (I only do small buildings so no deep plans with artificial lighting).

While it might not be quite as good as the HDRI based renders I used to do with Cinema 4D, it is very close and is pretty much a one button press exercise that saves me hours of fiddling.

With some tweaking of Levels with an adjustment layer in Photoshop the results are normally very good.

I was going to buy 3DS Max Design but after trying the 30 day demo I think I'll stick with just RAC 2009 for the moment.

[charliep]

Anyone still interested in this? Its v2013 and still a problem hence my getting to this thread. Anyway, the model I'm working on, no matter what I did with the settings it came out black. Then I remembered I'd done a similar one a while back which came out OK. I compared the 2 models, the settings were identical, the lights were the same also the windows. The only difference was the distance the camera was from the target. So I pulled back the camera and hey presto! I had a rendering I could use.