Interior Rendering Daylighting Contrast

[kfilar]

Using VRay for SU v.01.05.30 (we had to revert back for some reason known only to our IT dept)

 

I'm brand new to VRay, and totally appreciate that I'm only going to fully get my answers through experience. However, I thought this might be a useful question. I've looked at many threads that discuss interior lighting settings. Multiple experts seem to prefer wildly different settings for exactly the same scene, and they all seem to work, because there appear to be many settings that affect brightness:

 

ISO

Shutter Speed

F-number

GI (sky, in my case) Multiplier

GI Texture Common (Sky) Multiplier

GI Texture General Intensity Multiplier (I think this is another sun multiplier, but it's unclear)

Background Multiplier

Background Texture Common (Bitmap) Multiplier

GI Contrast Base?

 

I'm probably forgetting a few, or not sure what all the setting are that I'm using. But in general, it seems that increasing the ISO and decreasing the shutter speed, for example, might balance eachother out and give you very similar, if not exactly the same, output.

 

What I'm hoping to find is the magic variables that allow me to decrease the contrast between the daylight coming into the room and the ambient lighting inside the room. I see a lot of people put hidden rectangular lights on the windows, but I was hoping to find a setting that doesn't mean adding this construction.

 

To put it another way, I want to brighten the interior of the room without changing the sunlight intensity directly hitting the floor, or keep the interior brightness and decrease the sunlight intensity directly hitting the floor. Either way, because I have so many ways to easily change the brightness of everything.

 

Thanks in advance.

[fadi3d]

good luck with that and if u succed pls let me know, i've been trying so hard to replicate this scenario where i use only Vray sun and sky to light an interior with no luck at all, when the scene is Bright enough i get al lot of burnet areas where the sun hits the floor and walls and if i fix that with the camera exposure the the scene is not bright enough.

keep it up.

[abmitalia]

Hm-I tell you what u want. ... You want a physically correct render show a not physically correct image. Thats why it doesn't function, and thats why there are so many lightning tutorials out there. Fotografers use extralights and blured mirrors to lighten up interiors - models - furniture etc. so does the professional cg illustrater. Often that what seems to be the effect of one light is composed of 2-3 or more unvisible lights added because the picture is made to be brainrealistic - not fotorealistic in order to be beliefable. RK

[kfilar]

My problem is that I'm not a renderer. I'm an architect. So, I'd like to get as high a quality output for the least amount of CG/renderingtime.

 

I had some initial success yesterday with a few things:

 

1) I turned down the multiplier on the Background Bitmap by an order of magnitude. That got my background sky bitmap much more reasonable in this interior shot.

 

2) I turned down my Sun multiplier so it wasn't burning out the neighboring buildings outside my building.

 

3) Then I turned up the multiplier on the Secondary Engine (Light Cahche) from 1 to 2. Didn't look like anything on this planet. Turned it back down to 1.1 then 1.2. It helped a lot to brighten the interior without increasing the daylight. I noticed I started to get brightly colored artifacts at 1.2, so I increased the Primary Engine (Irradiance) multiplier from 1 to 1.1 and dropped the secondary to 1.1. Still got some artifacts, but both of these techniques brighten the room without brightening the exterior/daylight. I was hoping that by increasing the quality of the image (Irradiance Map HSph. Subdivs from 20 to 50 and Light Cache Subdivs from 150 to 2,500) I might eliminate these artifacts, but Sketchup crashed at some point last night so I don't know yet.

 

Am I on the right track here, or does someone want to persuade me to not mess with the Primary and Secondary Engine multipliers?

 

If I get something I'm somewhat happy with, I'll post the settings and major processes.

[abmitalia]

Well - everything u did try out does influence of course the brightness in the separted spaces you have. Somebody use this kind of tecnique somebody doesn't want to use it for several reasons. Using diferent light sources does it make much more easy to control them seperately and reaching that what u try to reach in a much more comfortable way without influencing the render time too much. You can also reduce the GI receiving property of single objects - that helps the burning out effect. Remember .. A lot can be done in aftereffect in PS. RK

[Nic H]

you are on the wrong track unfotunately! (dont mess with 1st. 2nd bounce multipliers - you get weird artifacts)

try lokcing your ISO and Shutter speed on the same value (100, 100) and expose using only the FStop for a quick and dirty set up.

 

Try reinhard colour mapping wth the burn value on something like 0.2 or 0.1 and expose to suit. You should get a pretty decnet image, it may be lacking some contrast however.

 

If you are game read up on LWF...however Id try reinhard with just sun sky phys cam for now, and maybe introduce some plane / flll lights if needed. I wouldnt go above 1000 for LC either, its not really needed. Start with something like 20/50 -1, -5 for Irr map as well.

[kfilar]

Thanks nicnic,

 

I'm going to do one more test with the bounce multipliers, but I'll give up quickly based on your suggestion. I presume the F-Stop solution is just a way to adjust the brightness with one setting vs. 3. Which makes sense, thought I presume it also affects the depth of field if that's turned on, but I haven't looked into it.

 

The reinhard color mapping doesn't seem to be selective for bounce lighting. Though it does seems to have a setting to not affect the background, but that's not enough. I'll try some of your other settings like 1000, 20/50, etc. Looks likel you've got -1 for min and -5 for max, or is it the other way around?

 

I will see if LWF has anything that looks like it will help.

 

Thanks very much,

[kfilar]

OK, my thoughts so far:

 

I can't get 2nd Bounce Multiplier to behave, so I'm leaving that set at 1, but I liked the effect and may go back to adding a lowish setting of 1.1 if I can eliminate the artifacts. However, Primary Bounce Multiplier I seem to be able to adjust and pretty much get what I want without having to set up light portals. I can brighten the interior without affecting the incoming daylighting. I've tried setting Primary Bounce Multiplier as high as 2, and I don't seem to need more than that. I am thinking that the more interior lighting I want to invest in, the lower I will need to set this multiplier.

 

Switching to the Lanczos antialiasing filter seemed to eliminate some artifacting, especially the rings I was seeing around lights, but I'm just starting to play with these settings, and everything seems to be affected by everything else.

 

I liked the idea in principle of keeping the ISO and shutterspeed fixed, but adjusting the F-Stop to brighten seems like the wrong way to go if I ever want to use depth of field. I would think I would want to set the depth of field the way I want it, then adjust one of the other two to get brightness.

 

I have to say I see a lot of very nice interior renderings on-line where the exterior window light is completely white. Those may be the "correct" light levels, but I don't think it corresponds to the way we perceive views with high contrast. I think our eyes/minds do a lot of adjusting, and what we perceive is less contrast. It may not be "correct", but I think I prefer to have interior renderings that do the sort of corrections that we do biologically. This seems particularly important when an architect is trying to demonstrate what a nice exterior view there will be from an interior space. Just my newbie 2 cents on that.