Painting in lighting effects

Hi,
I was wondering if anyone could give any advice or point me to any specific tutorials on the technique of painting in lighting, shadows, and maybe even some specular effects by hand in photoshop. So far I have been using lighting effects in Maya to get these things but I thought I would try my hand at doing it manually. In theory I should be able to get much better control by painting the effects in by hand.

I'd say you've got equal control in each. The difference is just in the methodology, not in the capabilities of the tools themselves. It's really just a question of what you're most comfortable with. For every person who argues in favor of hand-painting, there's another who will prefer to work procedurally. Both have pluses and minuses in terms of the amount of work/thought that has to go into the texture at hand, but equal results can be achieved with each.

For me, the question of which method to use will be determined on a project-to-project basis. Sometimes it's one or the other, sometimes it's both. It all depends on what's going to most efficient for specific project at hand.



When I do lighting/shading in Photoshop, I usually work subtractively. A common mistake I think a lot of people make is try to "add lighting" to a texture. That usually doesn't work out too well, since most base textures are created as if they're already fully lit. Making them "lighter" just ends up making them looked unnaturally washed out. It's usually far more effective to go the other way around, "subtract shading" FROM the texture, don't add lighting to it.

Here's an easy example. Take an ordinary texture that you might use for flooring. Maybe something with tiles or boards on it. Put a solid black layer above it, and give the black layer a mask. Now, Put a black-to white radial gradient on the mask, with a lit of black in the center, fading to white just at the very edges of the canvas. Right away you've got a floor that looks naturally lit, not just a flat texture. Under most normal lighting conditions, real floors always have shadow on them near the the walls, especially in the corners, and are lightest toward the center of the room, and that's exactly the effect we just created.

By blackening the whole thing first, the question becomes in what places do you remove shadow to show the lit texture in its natural state. Make sense?

To do lighting by hand in PS I usually duplicate my skin or clothing item onto 2-3 layers. I make one my shadow layer, one my specular layer, and perhaps one a diffuse shadow layer or scattered specular layer, and I use levels and saturation adjustment layers to alter each of those layers for the way I want those lighting elements to look. Then I use layer masks to reveal each element in the areas I want it to appear. The nice thing about doing it that way is that it's completely non-destructive and generally much faster than trying to use dodge and burn or other painting methods..

That makes a whole lot of sense, both of you. Thank you very much

One thing I am still not quite clear on, though. I get the idea about the taking away of lighting and not washing out the image, and also what Chip is saying about the layer usage.

I'm still not quite clear about techniques when adding something like specular where the light, at least in one small part, shines and makes the color completely gone. I'm not quite sure how to make that effect look realistic especially when it comes to shaping and placing the light parts.

Specularity can be tricky to do realistically, but it helps if you keep in mind how specular light behaves on various types of materials. Specularity is directly reflected light and the way it looks is influenced by a couple of main properties of the material.

The first property is how reflective the material is. A highly reflective material like PVC will show a pure white specular highlight. A material that isn't reflective, like denim, will just show a lightening of the fabric color. So you can think of the range of specularity between there being no affect on the basic material color up through it turning pure white as the measure of the materials reflective quality.

The second important property that affects the way specularity looks is how rough or smooth the material is, which alters how the area of specularity blends in with non-specular areas. A perfectly smooth material will have a sharply defined edge to specular reflections. A rough material, which would scatter specular light, will have a gradual blending from the area of specularity to the surrounding diffuse light. The rougher the material, the wider the dispersion.

We can relate those material properties to brush properties in Photoshop. Shininess/reflectivity relates to brush opacity. The more reflective the material, the more opaque your brush should be (because the shinier a material is, the more the specularity will hide the underlying material color). Smoothness/roughness relates to the brush edge properties. The smoother the material, the sharper the brush edge (because more light is being reflected). The rougher the material, the more diffuse the brush edge (becuase more light is being scattered by the rough surface).

Thank you again Chip that is very helpful.

At the risk of you all getting tired of my questions (if you're not already) I have another one.

I was wandering what people thought about the balance between putting in your own shadows and lighting and going with the lighting within SL. Giving it some more reconsideration, I think in my quest for making things look eye catching and realistic, and oooh shiny, I might be getting a bit carried away.

The problem comes, as you all know, when you bake in shadows and lighting for an object presuming light is coming from one direction, and then it gets put somewhere in SL where the nearest source of in world light from the total opposite direction and suddenly your baked in shadows and lighting makes no sense.

So my question is, where is the line between making something look realistic and dynamic and still allowing it to look like it make sense wherever it might be placed in world? Of course this doesn't count when you're making entire enclosed rooms where you can permanently fix all the lighting in the places of your choosing.

Good question. I usually try to light most scenes as neutrally as possible. I go for the "overcast day" type of shading in most cases, lots of ambient lighting, diffuse shadows, very little direct lighting, almost no obviously directional shadows. This way, whatever direction the sun is in, the shading looks plausible.

It's kind of like the way good sculptors will focus the eyes of their characters dead center, to create the illusion that no matter what angle you're at, the statue is looking at you. If you keep your shading "centered", the observer will get the impression things are visually correct under the widest possible range of conditions.

Here's a pretty good example of what I mean:



Where's the sun in that photo? It could be directly above, it could be in front or in back, or off to either side. You really can't tell. All you know is that surfaces that are facing down are dark, surfaces facing up are bright, and surfaces facing sideways are in between. Each object's shadow, including those of the two people, fall pretty much directly beneath them.

Light your scene that same way in SL, and it will look plausible all day long. It won't be technically accurate to the actual sun, of course, but no one will notice.

Now here's an opposite example:



There are number of dead giveaways that the sun must be in a particular direction. The shadows are not directly underneath the umbrellas, but are offset to one side. The footprints in the sand are all shaded on one side, and lit on the other. The highlights on the vertical umbrella shafts all face that same direction.

You'd never want to light any outdoor scene that way in SL, unless it was on a private island, with the sun locked in place. Otherwise, as soon as the sun moves, the illusion would fail, and the scene would look even worse than if it had no shading on it at all.



The main goal with baked lighting/shading is not to create a perfectly accurate lighting scheme, but to merely to eliminate flatness. You want your baked texturing to make your work "pop". It doesn't have to follow every last law of physics in order to be convincing. As long as it looks less fake than everything else around it, it's "real".

For enclosed indoor settings, by all means be as directional as you want. But for outdoor stuff, keep it neutral.

I'm still experimenting with finding the right balance with the new lighting system. I think adding lighting effects is still very useful in making things look realistic, but you're right in that you can overdo it to the point where it conflicts with SL's own lighting. If you stick to overhead lighting that's fairly diffuse (meaning it casts only subtle soft shadows) your stuff will look fine in most situations.

Edit to add: Yeah, what Chosen said

You guys are awesome, thank you very much!

Having a better understanding now of the above issues, it leads me to yet another question. Now I would like to look at the issue to terms of performance.



Okay, so now I have my naturally lit 20x20 meter floor that no longer looks like a flat texture. The thing is, what was once a little tiny 64x64 texture tiled now has to be a single much bigger texture, maybe 512x512 or 1024x1024 since it's such a large floor space. I would like to know the best way to handle this.

From what I see, I could either:

a) Upload a single 1024x1024 texture and offset it on each of the prims that make up the floor so they fit together properly to make up the whole floor
b) Split the texture up in Photoshop and upload 4 different 512x512 textures one for each of the 4 floor prims
c) Do something even better that I haven't been able to think of.

Any suggestions?