Unfortunately, lighting a highest-quality render in SH3D -- or, for that matter, virtually any ray-tracer -- is as much an art as a science. If you look through the gallery forum, you'll find many of the best-looking renders may use a dozen or more light sources -- per room. And if you spend some time digging through the threads, you'll find there are nearly as many theories of how best to light a scene as there are users of SH3D. The good news is that while the learning curve can be steep, it's usually blessedly short: An hour or two devoted solely to lighting, and you should be comfortable dealing with pretty much any scene you can concoct.
I'm going to describe my approach -- but keep in mind what seems intuitive to me may make little sense to you. (When I first started working with SH3D, I slogged through the posts and tried to imitate scenarios that worked beautifully for others -- most notably the 'stacked' lighting array that places several large, relatively low-power lights at a single [x,y] location but at different elevations -- for instance, 2-foot diameter lights at 15% power at 2', 4' and 6' heights. No matter what I tried, my renders were always godawful, while the ones in the forum -- using the same settings -- looked great.)
First, though, some handy generalizations:
- First, un-check the box that says "Add ceiling lights." When checked, this places a single small light source at 50% at ceiling height at the calculated center of the room. This is typically (a) too bright a light, (b) too small a source, causing harsh shadows, and (c) an unattractive place to hang what is, essentially, a bare bulb.
- The smaller the light source, the sharper-edged the shadows it throws. Conversely, larger-diameter light sources throw softer-edged shadows.
- For the most part, SH3D does not support ambient lighting. Many ray tracers have a separate 'ambient light' value, which in effect causes objects to glow, slightly, emulating the effects of ambient lighting in the real world. ('Ambient light' refers to how, In Real Life, shadows are rarely jet black; instead, even heavily shadowed areas are illuminated, however dimly, as a result of stray photons bouncing off essentially everything else within eyesight, with some randomly continuing on to illuminate [a tiny little bit] an area that otherwise lies in shadow.) While SH3D does include some ambient processing, for the most part you'll want to supplement it with 'fake' ambient lighting generated by large-diameter (e.g., 3- to 6-foot), low-power (5 to 10%), low-elevation (1" to 2') light sources.
- However, if you do use large, low-elevation light sources, make sure they don't intersect or overlap walls, floors, ceilings, or items of furniture. A collision between a light source and, well, anything else woll cause a dark circle to appear on the anything else.
- You'll find a number of light sources in the furniture library under 'Lights.' If I recall correctly, as they come, unaltered -- that is, as they appear when first dragged into a scene -- they appear as roughly 3.5" spheres (about the diameter of your standard light bulb) at an elevation of around 7.65' (aka 2 meters) and 50% power. (In my experience, that's far too powerful a light; I usually drop that to 20 - 25%.)
- You'll find lights configured to have color temperatures roughly comparable to incandescent and halogen lamps. There's also a 'white light source,' which provides pure, balanced illumination of a sort not found in nature; you'll probably find it makes your renders appear a little unreal. You'll also find a collection of colored lights, which will come in handy if you ever need to model a 13-year-old's bedroom.
- Some furniture items -- mainly lamps and lighting fixtures, amazingly enough -- come complete with an integral light source; it's also possible to create or customize your own fixture + light source. It's a moderately painful process; should you somehow feel compelled to try, the place to begin is OK Hoff's excellent paper on SH3D and SVG.
Personally, for interior scenes, I've had the most luck when I begin by imitating how the scene would be lit in real life.
First, I place small (1" - 3") lights near the ceiling, more-or-less in the locations where ceiling fixtures would go. (I typically use a 'ceiling fixture' object, containing a small -- 1/4" or so -- light source, along with a 'parabolic reflector' and a slight rim to prevent spillover from burning out the ceiling when rendering from a low-elevation POV. However, before I became so anal about it, I had perfectly acceptable results using a 1" light source elevated to [ceiling height - 0.5"].) I usually start with a power of 25%, but may later drop that to as low as 15%, depending on the total number of light sources in the final scene.
Second, I place small, very low-power (5% to 8%) light sources in any non-ceiling light fixtures: wall sconces, swag lamps, spot or flood lights, task lights, table lamps, and so on. I've gone as low as 2% for special-purpose lighting (for instance, a lamp built into a piece of machinery intended to illuminate a work surface).
Third, I generate a high-quality (Q4) render -- which, more than likely, looks like... well, doesn't look very good, usually because there are large areas that are either underlit (dark) or poorly lit (overly contrasted). These I try to correct by dropping in large (1' to 5'), low- to medium-powered (usually 8% to 15%), low-elevation (1' to 5') light sources.
To avoid burned-out (overly illuminated) spots on walls or furniture, I try to keep lights at least 2' from the nearest anything else. This sometimes limits the maximum usable diameter: For instance, if I have a 3'-tall sofa in a room with 8' ceilings, the largest light source I can use is one 1' in diameter (3' + 2' = 5'; 8' - 2' = 6'; therefore, I can only have a light source between 5' and 6'). (In the previous example, I would probably create several 1' diameter lights at 5' elevation and, say, 8% power, and position them 2' to 3' apart.)
Of course, once I've placed a couple such 'fill' lights, I generate another Q4 render, since the addition of fill-in illumination may be enough to cause my primary lights to burn-in. In that case, I'll drop 5% off the offending ceiling light source(s) and render again. Render, tweak, render, da capo....
With a little luck, eventually it looks the way I want it to look.
I hope some of this helps -- and, let me assure you, it's nowhere nearly as difficult as I've made it sound!
maz
