Background lighting...

[ThreeOhFour]

Howdy all,

I am hoping you will be able to assist me with my little problem. I am working on this background and I am unsure as to where the yellow lighting should start showing on the walls and the floor. As you can see I have made a start, but I do not feel that this is correct. I would like to get this aspect right before adding more things to the room.



Any help you could render would be greatly appreciated. Also, if you see something else you feel could be improved please point it out.

Thankyou in advance.

[ildu]

Depends how much ambient light (apart from the shown lightsources) from off-screen lights there is in the image. Supposedly there's some kind of red ambient light, or at least it looks like it. This has an effect on how well light from specific lightsources (like the yellow one) are seen, and moreso on how they mix. If in fact there are no other lights than those seen in the image, we should be seeing a lot more contrast in the lighting, and more dark areas.

Seeing as the wall there is curved, and the yellow lamp is indented, geometrically there would be no direct yellow light cast on the walls adjacent to the curved wall, only light being bounced via other walls. Normally the direction would depend on how wide the lighting area is in contrast to the indentation depth of it, making it show a shadow/light line on the walls, but I'm pretty sure that with a curved light area it wouldn't show. The light cast on the floor is different because the lamp is straight vertically. What you've drawn on the floor is pretty correct - A small sharp difference at the beginning, with steady fall-off towards the direction of light, as well as on the sides (especially because the source is curved). I would except the light fall-off not to end so quickly, but rather continue off-screen, though. And btw, we should see the same light emitted on the ceiling as is emitted on the floor.

Flat lights are a difficult thing to understand and implement. If you'd assume that there is an infinite amount of lightsources making up a light area, you could say that the light area emits light ideally in a direction perpendicular to the area. Since nothing in life is really ideal , the practical use of a flat light would be to have lamps underneath as lightsources with a glass on top dispersing the light, which would mean the range of light directions from a flat light could be anything, really.

You can try this at home: Turn off all the lights in your room, except for your monitor. You should immediately see that the wall behind the monitor, and probably adjacent walls will be pretty dark. Lift your hand or for example a piece of paper next to the monitor so that it's aligned up with the monitor window. Whatever you lifted up should be really dark (not pitch black, unless there's nothing to reflect the monitor light back). Slowly rotating your hand or whatever 90 degrees towards the spot where it's perpendicular to the monitor window, you should see a pretty steady rise in light emitted on the hand or whatever.

You can also experiment on how the different colors and brightnesses on your monitor affect the lighting in your room. For example, if your desktop image is red, you should be seeing a slight red tint. At the same time, you can compare google.com with a white background to its energy-saving variant blackle.com with it's sleek black background. You should see a significant difference in the amount of light emitted within the room, not to mention feel a certain satisfaction in aiding the issue of energy consumption .

[ThreeOhFour]

Thankyou for your advice.

Apart from the door, the wall light and the small lights there are no other lights. There will be a computer screen later on.

I've done a sloppy edit of the background, adjusting the lighting as well as the colours. Again, your advice is appreciated, as well as any further advice on the picture.



Thanks.

[Khris]

Yeah, areal light sources are a bitch to handle.



As you can see from the above, exaggerated illustration, the part of the wall marked black doesn't get any direct light.

The transit from dark to lit is always fuzzy, too, especially if the shadow is far away from the object casting it. So the desk's shadow should get fuzzy very quickly.
The bigger the area of the lamp illuminating the area, the broader the fuzzy transition.

The drop shadow beneath and above the lamp isn't correct either. Both areas are illuminated by roughly half the lamp's height, resulting in a smooth transition, too.

[thebaddie]

are you sure it's the correct image? it seems a mask


Edit by ProgZ:  Please don't quote posts directly above yours.

[auriond]

It's a simulation of the room from top view.

I agree that the shadows probably need to be a little stronger, but it depends on the strength of the light source. Right now it looks like a gentle neon glow, like for ambience, and this wouldn't cast very strong shadows if there are other light sources (as there seem to be in your current). But since you mentioned that it's the only major light source, then the shadows would have to be much darker, and on top of that the light itself would have to look much brighter - almost white towards the middle where the bulb is. That would be bright enough to light the whole room.

[paolo]

Ben,

KhrisMUC's diagram is excellent. I suggest you sketch something similar, and then do the following:

* Subdivide the indented curve (the part that is emitting the light) into (say) 6 equal-sized regions.
* Draw a straight line from the centre of each of these regions to the right edge of the indented region and keep going until you hit the wall.
* Do the same for the left edge.
* Each of these lines represents 1/6 of the light emitted by the light source.
* On each side, the highest point reached (in the diagram) will be (roughly) the furthest point back that is illuminated by the light. Points further into the corner are not illuminated by this light (but might be illuminated by other light sources or by ambient light).
* Moving out from the corner and looking at the lines you've drawn, you should get a some idea of how the light changes from shadow to full-on brightness - where rays meeting the wall are bunched-up, you've got a lot of light, and where they are spread out, there is less light.

I'm not sure how clear that is, but hopefully it helps a little.

You could go into the physics of it all (the strength of a light drops off proportionally to the square of the distance from the light source, and the amount of light reflected off a surface is proportional to the cosine of the angle between the ray coming from the light source and a line at right angles to the surface) but then you'd be better off simulating the room in a ray-tracer and seeing what result you got. It will look best if you do it by eye.

EDIT: Of course, the curved walls of the light don't receive any light from the light itself, unless they are translucent.

By the way, the room looks really cool!

Another suggestion... if you can, get hold of a fluorescent light bulb, mask it with opaque tape like your light, and stand it upright in a corner in a darkened room to see what the pattern of illumination is.

[Oliwerko]

Wow, this one is a great BG!

I would stick to what Khris and paolo already said, draw a diagram like that on paper and think about which walls are illuminated and which of them are not. It really helps to draw it first, you can get a much better idea of what is going on in that room. Using this technique you can also get the direction of shadows cast by the objects in the room.

OT: I reaaaaly like that background, is it going to be some kind of BASS sci-fi? I really love those classic sci-fis.

[Cluey]

Sorry for the low quality it was just to show you how the light would fall, note the darkness areas in the top and bottom corners. Other than that, you were pretty on the ball with the radiosity.

[ThreeOhFour]

Thankyou KhrishMUC and Cluey for your images. They are both very helpful.

I've done another version, mainly trying to get the shape of the lighting right. I have a feeling that the light may not be bright enough on the wall and the floors - Cluey's has very bright bits. Should I adjust it to allow for these? Also, let me know of any other changes you feel need doing.



Oliwerko, I am glad you like the background. I am not sure how to describe the game this background is meant for, but it is going for a slightly futuristic feel. Hopefully if we stay on task you'll see something soon.

Apologies for taking so many attempts to get it right, by the way. I am sure I'll have this one finished soon enough, and thanks again for your advice.

[paolo]

I think this is looking pretty much spot-on now.

The carpet will be illuminated by the light coming through the door as well - I take it you know that and are already intending to do it.

I think you do need very bright patches on the floor and ceiling like Cluey has done - if you draw rays from various points in the light towards the floor and ceiling, they will all will reach these areas, and as the floor and ceiling are close to the light, the light there will be concentrated.

[Galen]

No light beam coming from the light in the empty hole.

[ThreeOhFour]

I feel that this image nears completion. I have added in the discussed things. I am unsure as to whether I have accurately shown the light from the door however. Your thoughts are appreciated.



Cheers

[Evil]

I don't know much about lighting, but I'd think it'd look something like this? Also, for as long as the shadow is from the desk, I'd think there would be some dark places on the wall. Same with around the door, because the light source is bright.

[Oliwerko]

I think the transition between the shadow and illumination on the walls near the light source is a bit steep and fast. I would use a longer gradient there...

[auriond]

Something about the shadow  of the desk bothers me. It looks like the shadow of a much larger object. Cluey's version has the right kind of shadow - it gets lighter away from the desk because the light source is tall, and some rays of light would be coming from above at a different angle.

[Cluey]

Cluey's version has the right kind of shadow - it gets lighter away from the desk because the light source is tall, and some rays of light would be coming from above at a different angle.

It was done with a VRAY renderer, so it's pretty accurate.

[LimpingFish]

In fact, the rays closest to the top of the light source would miss the desk completely, so the shadow wouldn't be that long.

I also did a 3D version of the basic scene layout, and got pretty much what Cluey ended up with.

The shadow would seemingly end...



...more or less.