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gym1339

Color shift on textures with Final Radiosity

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I have been working on a "simple" design project for a schoolroom with four exterior windows and some fluorescent fixtures. The client has designed some graphics to adorn the drab walls and "bring the creative energies of the room to life." Okay, so she is very particular about the color of these objects. I have spent hours manipulating these textures in Photoshop and have mapped them to the objects that will hang on the walls. My initial renderings were done in Final Quality Rendering mode with the default lighting. She was "okay" with these results, but she wanted a more impressive presentation. So I added some directional lights, spotlights, and ambient light to render a portion of the scene. It looked pretty fantastic, but I only rendered a small portion of the room. Is it common practice to create an extensive lighting rig filled with lights to render a scene in Final Quality Render works? I have already used to 12 lights to render about 1/8 of the room. The file size is also huge, I must be doing something wrong. So I went to a different solution.

I used Final Radiosity and created four area lights to simulate the sun entering the four windows. I added a directional light for the sun itself and rendered away. The softness of the light looks fantastic, but the color has shifted dramatically on the objects. This just won't do. Any ideas as to why the objects' color of red would turn to a fluorescent orange? I tried moving the area lights, changing the lighting layers ambient values and even tried to alter the texture to a matte finish and tweaked the ambient and diffuse settings. I set the area lights to 20,000 Lux and a color temp of 5500K. I have placed these just inside and just outside the windows with different results, what is convention?

Any thoughts on Rendering modes, lighting techniques, radiosity settings, texture setiings, etc. would be greatly appreciated. So much for a ?simple? project.

Thanks in advance,

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Hello Jim:

It is hard to say why the colors are changing without seeing the file. My guess is that it is the auto exposure, which is on by default in FQ radiosity mode.

I just did a lighting presentation for the NYC user's group last week and I'm trying to record this in a form that can be used here on the forum. My recommendation for interior lighting for is just what you tried - 20000 lux for area lights just inside the window glazing (so the glazing, mullion, etc don't cause noisy shadows), set to a very pale blue color (I only use color temp for electric lights, it is too colorful with natural lighting), and a directional light with very pale yellow and also 20000 lux. You may try changing the directional light to footcandles then back to lux to make sure it "sticks".

I do not use ambient light at all with radiosity as it just introduces a gray haze to the image.

If you can send me the file I might be able to help more. The large size is either from the radiosity solutions being saved with the viewport cache (you can change this in the document prefs) or a lot of images in the file. Rendered viewports with caches can be quite large.

Does the layer and viewport lighting options white balance color temperature match the lights' color temperatures?

HTH,

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Thanks Dave, Maybe you could explain some terminology:

Auto exposure, what is it and how can I use, or not use it?

How does VW define "Lux" vs "Lumens" in the brightness unit box?

My area lights are set to dimmer 75% dist fall:sharp and render geometry:off show direction:on. Are these good to start with? What do you use with your light blue setting?

The directional light, how do you use it. I noticed if you are using a pale yellow, is this to represent ambient "electric light" because of its warmer color? As opposed to sunlight with its cooler color? What are some of its settings?

All of my emitter white balance settings are set to 5500K. How does this relate to lighting fixtures if I go in an manually change a light to a differnet color temp. Do the layer and viewport settings influence this?

I will probably send you the file, but I want to tweak as much as I can to understand what I'm doing.

Thanks so much,

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In the Custom RW and Custom Radiosity options is a checkbox called "Auto-Adjust Exposure", when it is on RW adjusts the pixel luminances so that the brightest and dimmest parts are more visible in the image. This is on by default for the radiosity modes, and is an option for CustomRW mode.

Lux is lumens per square meter, and is useful for area lights and directional lights. It is helpful to put both the "sun" directional light and the "sky" area lights into lux, so that the balance between the cool and warm lighting can be controlled in a straightforward way. It is also very useful to put area lights in lux because then windows of different sizes will have consistent even brightness. The only time I would use lumens for an area light would be if it were some kind of panel with electric lights behind it of a known total lumens value.

I would set the dimmer to 100%, otherwise you are seeing 75% of 20000 lux. Your other settings are fine.

Are you mixing electrical and natural lighting in the same rendering? I set the directional light to a wamr color because the sun appears warmer than the sky.

If you have the white balance set to 5500, lights with K lower will appear more yellow or orange, and lights higher than 5500 will appear blue. Each layer an viewport has its own white balance setting; each should be set appropriately for the lights that are on in the layer/viewport.

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I have unchecked the "Auto-adjust exposure" box in custom radiosity settings. I have turned off the ambient layer light and have set the dimmers to 100%. Now when I render, my scene is over exposed (very very over exposed). I made the area lights a pale blue color. Any other settings I am overlooking? Also, my ceiling has a grid texture and does not render in radiosity modes, but does render in final quality render mode, why?

Thanks again,

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Jim,

There are no easy answers to setting up lighting.

If lights are too bright/dark do another test at 50%/200% of existing levels. If still way out of whack change by 10%/1000% of original to determine the general levels required before getting down to tweaking.

To make things faster to do test renders, set the Custom Radiosity settings to low accuracy, NURBS, etc, and turn off anti-ailiasing.

Also reduce the actual perspective window to reduce the render time.

HTH,

N.

Edited by propstuff

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Nicholas,

Thanks for your insight that "there are no easy answers to setting up lighting." I'm not looking for any. I am merely trying to understand how different lights react with different settings in different rendering modes. I'd like to approach my renderings with a more systematic approach then merely cranking up dimmer values or adding more lights. In fact, I wasn't aware that the auto-adjust exposure was on by default in final radiosity mode. According to the documentation, with auto-adjust on, the overall brightness will never exceed a certain level. Therefore, could your approach to changing the existing levels to 200%-1000% be counter productive if the overall brightness of a scene will never surpass a certain level? I don't know, maybe you have some insight.

Obviously Dave has a firm grasp on rendering techniques, and if he says my dimmer values should be at 100% and my renderings are over exposed, I want to know why. Not to say, this is the only, "easy" way of setting up a lighting rig. It is merely an approach that I can learn from and use what works for me, and at the very least, understand the program better.

So if you have any tried and true suggestions, I'm all ears.

Thanks,

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Hello again Jim:

I always use auto exposure. When it is on you do not have to worry about absolute brightness as long as your lights are consistent relative to each other. The easiest way to keep them consistent is to use accurate values for all of them. I do not mix the % brightnesses with the accurate brightnesses in the same scene. Auto exposure also shows indirect lighting better than not having it on, because the effects can be pretty dim and subtle.

Propstuff and I have been figuring out useful lighting techniques (pre-radiosity days even!); his conclusions are to use a smooth falloff and no auto exposure. My recommendation is to use sharp falloff and auto exposure all the time.

One thing I also recommend is to use the 16 electrical accurate lamp symbols from the Libraries folder. These have accurate light values assigned to them already. They use sharp falloff and will require auto exposure because of the brightness values.

If you can get the file to me that would help a lot.

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Jim,

As Dave said, he and I have been discussing lighting renders for a long time, including set-ups to make it easier to start. As far as "tried and true" suggestions are concerned; unfortunately,..well, everything effects everything else, and, well,..................... there are no easy answers... (well not many anyway)

I wrote you a detailed reply but lost it all to the "form no longer valid" bug, and I'm not going to do it all again.

Here are some examples though,

Area lights in the kitchen/dining windows (inclined inwards/downwards about 12?) each 1000 lux, 150%;

Area lights in the Entrance and adjacent doorways, each 1000 lux, 50%

All area lights at smooth fall off.

Sun 1000 lux, 3%

Radiosity 75% accuracy, 75% energy, ambient set to layer; 24%

Background; that particular HDRI set at 150%

Auto Exposure turned off

Picture%2027.png

Note : this was test render No 27 of the second batch of test renders of the same file; adjusting lighting at each test.

This is a another version of the file with similar settings and the Ambient set to "remaining energy"

P-40-rem.png

This is exactly the same settings, except Ambient is set to Layer Ambient (at about 20% I think)

P-53-amb.png

You'll note significant colour shifts even though the overall light levels are almost the same, and the file is otherwise identical. In particular; with the previous version, the Ambient "remaining" energy is applying the reddish tint from the floor texture to the scene and making everything (particularly the walls) look excessively red. By using Layer ambient I've tried to control that and make the white walls actually appear white.

One of the more "realistic" renders I've seen out of RW -even if I do say so myself ;-) is this one done in VW10, (prior to radiosity or HDRI) lit with a version of Dave's "skydome" object,.... and about 6 weeks of test renders every night.

DEVOTION-sml.jpg

Your project might be "simple" Jim, but lighting renders is not.

Try out the settings I posted above and let us know what happens.

HTH,

N.

Edited by propstuff

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Dave, Propstuff,

Thanks for your insight, really very helpful. I think I'm finally starting to grasp how I can set up some successful lighting rigs in VW.

Dave, correct me if I'm wrong: You set all lights to their "real world" brightness values, i.e. the sun at 20000lux. You use auto Exposure set to on, this ensures that all lights will have an absolute brightness value relative to one another. So to change intensities between lights, do you change only their brightness values and not their dimmer values? So if you wanted a light of 1000 lux set to 50%, would you keep the dimmer value at 100% and change the brightness value to 500lux?

Propstuff seems like you bring all the brightness values down, to say 1000 lux. You then adjust dimmer values relative to one another. Auto Exposure is set to off, and this allows each light to output without any forced exposure. I assume that by bringing the brightness values down, this gives you more headroom to adjust dimmer values to over 100%?

We have been discussing radiosity, when do you guys use custom renderworks options for a rendering, if ever?

I have taken your suggestions Propstuff by turning off some custom radiosty settings. Anything else I can do to speed up the test render process?

Thanks both of you for sharing some of your approaches to lighting. Dave I'll send you the file as soon as it finishes rendering!

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Hello again Jim:

I would probably change the lux values. I see the dimmer as something like an electrical dimmer switch, to change the values to temporarily lower values, rather than the main way to change the light brightness. It would be nice to remain grounded to physical units - that way you wouldn't get in trouble by specifying a 50 watt bulb running through a 1000% dimmer!

Since I am a gearhead and I know what everything does I often use custom. I use it because I can turn off things to control the speed. Usually with a radiosity scene you can set a few switches or sliders and save hours of solution time. I can usually generate a decent quality solution in 10 minutes and the whole render in 1/2 hour by adjusting the radiosity settings and mainly by controlling which objects participate.

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Jim,

That paticular experiment I used equal Lux values following Dave's advice that Lux is "light"/m2.

I was trying to establish the relative values for the different lights and I reasoned that if the lights all had the same Lux value, it would provide a "bench mark", and I would get a better idea of the relative levels. This logic might be completely erroneous, and I'm not suggesting that you should do it that way; it's simply illustrating relative levels that might work for you.

In general, I am just as likely to start with all the dimmers at 100% and go through the process of estimating and adjusting Lux levels that I outlined originally.

I have never been able to produce a radiosity render with Auto Exposure that doesn't look washed out and un-natural to me. Others like dave use it successfully, but after literally hundreds and hundreds of test renders, I'm damned if I can set up lighting that looks satisfactory to me.

I also use Custom nearly always because of the control. The exceptions are Fast Renderworks for setting non radiosity lighting levels, and Final quality Renderworks where radiosty is not needed and I dont need to tweak things extensively. HDRI is an example of the latter (and one of the few instances of "easy answers" ); radiosity can improve an HDRI, but generally the results are so satisfactory that it's not "needed". The amplifier enclosures above could have been lit with HDRI and tweaked in days rather than weeks!

Another tip:

My experience is that setting Energy levels much above 75% doesn't have much effect on the quality of the render, but increases time considerably. On the other hand, increasing Accuracy to 90% (from say 75%) improves the smoothness of the lighting a lot, but does not effect the time significantly.

N.

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Okay, now I come to another issue, how does one best present these renderings? Let's say you've set up your scene, the lighting and radiosity settings, and you let your machine render. An hour and a half latter you create a viewport to save what you got. The candy cane stripe appears, you update the viewport, and it has to re-render! I understand why this has to happen, but its still a drag and I should have planned a little better for this process. Then I went back to my design layer, and another re-render.

The sheet layer was set to 72 DPI and the viewport view detail didn?t look that great. I changed the DPI to 300 and re-rendered, which took a long time. So you?ve spent all this time setting up a viable solution, it looks great on screen, what?s the best way to preserve the integrity of the image when you transfer it to another format? What are some good formats to use when showing renderings? I export .jpg ?s and .pdf?s many times so I can easily disseminate information. What do some other people do?

Any thoughts would be much appreciated. After all, a lot of time has been spent getting your renderings to a certain level of artistry; don?t you want to present them in the best light? No pun, intended.

Thanks,

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If you do the radiosity solution within a viewport and the document pref is on to save the cache with the file, then the radiosity solution will stick around with the viewport as long as you don't change something that invalidates the solution. If the viewport cache is saved then it won't require that the radiosity solution be regenerated, just rerendered when you change the sheet layer DPI.

I like PNG because it is a "lossless" format unlike JPG but JPG is a bit smaller. If you have a rendered viewport you can copy and paste the image to another program (like Preview on the Mac) then save it out as some other format.

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For your comparison:

(ignore the artifacts at the wall/ceiing junction, that's just bad geometry on my part)

This is the same scene set up as Dave suggested.

Area lights just inside the window glazing 20,000lux 100% Sharp falloff, pale blue

Area lights down the hall 20,00 lux 50% (100 was too much), sharp falloff, pale blue.

Sun 20,000 lux 100%, pale yellow.

No Ambient

No HDRI

Auto exposure,

Otherwise settings as before.

Picture 9.png

What you see here is pretty typical of the results I get whatever I try with Auto exposure turned on. EG;

The brown "rammed earth" wall is orange and over saturated.

The White walls, ceiling, kitchen, and refrigerator are almost uniformly grey and don't even look vaguely white.

The texture of the floor has no colour or definition.

The sun outside is way overexposed even though the sun spilling into the room is modest.

Generally it looks "dead"

As you can see; I can't manage Auto Exposure at all.

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I have to admit its some comfort to know others are having trouble with lighting using radiosity. Personally I think I've gotten so used to "faking" the lighting (both thru the manipulation of the lighting itself and changing the material attributes) under the raytrace engine that I'm having alot of trouble adjusting to both the HDRI system and radiosity.

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Dave, Propstuff,

I have spent the last several days trying to come up with a system for test rendering lighting rigs in Vectorworks. I was intrigued by Dave's comment that he could usually generate a decent quality solution in 10 minutes and the whole render in 1/2 hour by adjusting the radiosity settings and mainly by controlling which objects participate. Maybe you could elaborate on this, are you turning off classes of objects not in the render view? What are some of the values of the sliders and switches you are setting to save hours of solution time?

My experimentation has led me to a few other questions maybe someone can help me with:

How do you get white walls? What texture did you use Propstuff in your renderings? My walls always look grey at best.

The black artifacts produced by the junctions of surfaces; can someone explain what is happening? I have created molding in the room from an extrude along path, and there are distracting black smudges along the trim.

The objects I created to hang on the walls also produce the black artifacts. Is there a good method of ?attaching? objects to walls to avoid this?

Does a point light have a beam spread? I used a few to fill in some dark areas of my rendering. Do these lights merely occupy a point in space and have the same diameter of illumination? Is there a way to widen the coverage of these lights?

With directional lights, do they only affect the exterior of a building? In other words, the directional light seems to affect the interior of a room, only through the windows.

Any suggestions on how to fill in the darker areas of a rendering? I have read that low- level wide spotlights can be used to achieve this. I haven?t had any luck with this technique. Any ideas?

What are some ways to pair natural light through windows with interior electric light to achieve satisfactory radiosity solutions?

Thanks for all your help,

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I dont have time for a long reply, but Dave has written a good detailed guide for optimising Radiosity

knowledge base -renderworks

Also, if you search the forum, there are some detailed discussions on getting white walls to look white. It's an on-going problem that everyone has with RW

plenty to work through there..

cheers

Edited by propstuff

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