View Full Version : Dfacto's Compilation of Random Mini-Tuts
08-26-2006, 12:48 PM
Some mini-tuts.... FOR THE HORDE! (that's you guys)
These will be short, but hopefully informative and helpful. I don't have a plan or anything so I'll just do whatever comes to mind.
Corners and Shadows:
When there is ambient lighting (which there almost always is) and a lack of direct lighting, a certain shadow effect will be visible in corners, grooves, depressions, and other such areas where a given point will be surrounded by other surfaces. The effect is a subtle soft shadow that appears to "radiate" out from the sharpest part of the corners and which gets weaker with increasing distance from those corners.
Left is a flat shading, right is with soft shadows in the corners.
The same effect can be seen here in certain corners of the room.
A bright light shining right into a corner will wash the shadows out, and a very reflective surface will also weaken the effect, even though it is still there. As a rule, if the corner is being hit with direct light, leave the shadows out. If the lighting is indirect then add it in, becoming stronger as the light becomes weaker. Remember however that it should always be subtle, so strength is relative here.
Put these shadows in grooves and corners of all kinds and it will give your piece that extra bit of visual punch, and it really doesn't take much effort. :)
08-26-2006, 01:05 PM
I think you're gonna have to make this a bit more read friendly. Had to read every sentence 2-3 times to understand what you meant, but okay I'm not really into 3D programs.
Theres also some of it I don't understand. What is the lightsource supposed to be? A 360*360 lightsource hovering in the middle of the room?
And even if it was a omni light, I don't see why the areas near the wall should recieve less light if it has a direct view to the lightsource, perhaps even more light if you calculate in the reflected light from the walls.
Okay, now I've read through the wikipedia definition of Ambient Occlusion. As far as I understand its a way of lighting the works in the exactly opposite way of how normal lighting. We understand lighting as something that comes from outside and object and hits the object.
With Ambient occlusion, the object itself is the light emmiter and emits light according to a very simple rule. Light that reaches the "sky", e.g. the background makes the surface it was emitted from more light. Should light from the point it was emitted make contact with another surface, the light point will become darker.
So basically, if an object or potrusion is in view of a light emitting point the point will become darker according to how many % of the light that is blocked.
I can see how this could be somewhat useful for 3D rendering if you need to show off a model the best way possible, making sure the viewer can get a sense of depth without have to put strategic lights all over the place.
But I guess that's really where it's functionality ends.
08-26-2006, 01:14 PM
Editing as we type. :)
OK, edited. See if that makes more sense.
08-26-2006, 02:39 PM
First of all, ambient light is not the opposite of ambient occlusion. Ambient occlusions opposite is Global illumination.
Ambient light is a subtle "mood" light.
Second, I don't think the "living room" example is very good as an example of ambient occlusion. The "corner effect" where it is darker in the corners with the GI could be seen as the same effect you get from AO, but the reasons is exactly opposite.
With AO, the darkness is generated from the walls being the lightsource itself and having their value detracted the more surfaces they hit. It is a method made for scenes without a real lightsource.
GI is basically that surfaces reflect light from a lightsource, but since corners are the point furthest away from the reflected lightpoints the reflection light between the two or three sides that makes up the corner will become exponentially worse the further you look into the corner since those sides can only reflect almost solely each others increasingly detereorating reflected light.
I'm sorry Dfacto, I'm not trying to shoot down your project here. It's just for the sake of understanding.
08-26-2006, 02:57 PM
Actually I'm trying to explain the real life effect from the 3d standpoint. Whether the reason is the same or not isn't all that important, because the effect in real life is still equivalent to AO. That is why AO is used by professional 3d studios like ILM and is a must for any good model render.
I also think we're using different definition here. Wikipedia's ambient light isn't really what I'm talking about. Rather I mean this: http://computing-dictionary.thefreedictionary.com/Ambient+lighting
Ambient light is light that has no specific light source, but comes from all directions. In terms of AO, the engine assumes that ambient light is present, and then calculates the falloff by drawing rays from each point in a scene going outwards and seeing where they go. In real life, ambient light is present in the form of reflected light, and the effect occurs because of the way the light rays interact with a surface.
The difference between real life and the 3d version is that the computer fakes it by going through the process backwards. But either way, the result is basically the same and applies to both 3d models and real life.
I admit that I'm doing this backwards, but I have yet to figure out what the real life equivalent of AO's effect is. I'm not even sure that there is a term for those sorts of shadows.
08-26-2006, 03:18 PM
Well I guess this all goes around to if your talking about real life physics or how the computer think of them.
I don't think you will find something in real life that can make an effect that resembles AO's. The very thought of a lightsource having the very shadow it produces reflected back and affecting itself would make any physicist choke on his cofee.
Why would you want to reproduce the effect in reallife too?
Could be mighty interesting, but the very concept seems to defy anything we know about lighting.
08-26-2006, 03:28 PM
The effect doesn't defy anything, you're just misunderstanding what I'm referring to. Look at the corner of your room and there is a chance, depending on whether you have harsh lighting or not, that the corners will be darker. I simply want to know what that type of shadow effect is called (if it has a name), because right now the only thing that I know about which looks the same is ambient occlusion, which is unfortunately just 3d related.
That's the only reason I use ao, is because I have no idea what the real deal is which it mimics.
08-26-2006, 04:08 PM
Well, I'm not gonna be stupid enough to say "a shadow is a shadow", but it just seems like its a shadow that is produced from the lighting conditions of GI together with a diffuse surface as stated in Lambert Cosine's law.
Why do you want to know specifically what that shading is called? It's a shade that is just as natural as the one you get when the sun produces you shadow on the surface.
The conditions is a litle different, but that doesn't mean that it gets to have it's own name.
08-26-2006, 04:26 PM
So far I've noticed that a myriad of mundane light and color effects have special designations. Seemed possible that this would also have a name.
08-28-2006, 02:11 AM
On second though, forget the theory, I'll just briefly mention the effect and just let the pic show what happens.
09-13-2006, 04:57 AM
Maybe you can name it "dfactos theory of darkness"? o_O
It's a nice observation so kudos for pointing it out for anyone who hasn't noticed it (or payed much attention to it) before.
09-25-2006, 09:11 AM
I liked the tutorial. I learned something even if I didn't understand it very well :ugh:
I'm hoping there is going to come another random mini tut soon.
09-25-2006, 10:41 AM
And here it is:
BE LIKE MICHAEL BOLTON! GO THE DISTANCE!
Thanks to Missy for letting me use her pic as an example.
Anyways, I just took two parts and overpainted them.
Upped the contrast, put in darker shadows under raised objects, added stronger edge highlights and took the secondary green light, the coat shadow, and the coat highligh reflection into account, and generally tried to pop out detail and clarify shapes.
The detail in the original is good, but the color job is mostly flat and doesn't accentuate the detail. The first step is to draw it in, but the final one is to really make it live with the color job. I did a sort of cursory job here, but it looks better imo and only took me a few minutes of painting. If you do this stuff while painting you will get much clearner results. Don't wait until you're done to detail, do it along the way so that you can integrate shadows much more easily and naturally. Fine highlights and shadows come at the end.
One thing to note as well is that the original is very low contrast which washes it out. Put contrast in your pics to really separate the elements and make it pop out. Otherwise as least make sure that the character is a different color or value from the background. In the original the character is almost the same as the background, which is boring and lacks punch. Give the eye something to grab a hold of right away.
09-25-2006, 01:50 PM
Nice details. The boots leather part just looks a bit too metal'ish now.
Could be fun to see you do a total workover :)
09-29-2006, 02:29 AM
METAL IS FOREVER
Thanks to Nefastus for the source pic from this thread: http://www.polykarbonbbs.com/showthread.php?t=12345
Dfacto's quick guide to rendering shiny metal surfaces!
1) Your pic
2) Block in your main metal color (in this case I chose a dark grey) and then add in the basic highlights and shadows. I did this in grayscale, allowing me to simply use the dodge and burn tools. If you do it with the lighting color, then don't.
3) Block in some more, and start putting in finer details, like the plating, and the plating's individual highlights and shadows. Also, I put in a backlight. The main light is coming from the top back, but there is another light in front of the character which is illuminating the armor.
4) Put in hard highlights for the top light, and softer highlights for the backlight. Then, if you weren't working in color to begin with, add a color layer overhead and give each light's surfaces a color corresponding to the light's color. I made the backlight blue, and the top light yellow.
When doing shiny metal there are a few things that you have to remember.
-Reflections: shiny metal reflects. I did a quick job here, so you can't see that too much, but it does. Having it reflect it's surroundings is good, and even if it isn't that shiny, you need to have it reflect it's own highlights. The shoulder ball is a good example, with the side near the rim being lit up by the highlights on the rim.
-Contrast: Unless it's being bombarded by intense lights, there wil be very bright areas, and very dark areas. The dark areas will be the ones where the reflections are the most visible.
-Strong specular highlights: The light source will be reflected strongly, and this will look to the viewer like stark bright patches.
The ball bearing has a shiny but matte finish, but you can see that there are very bright spots which are reflecting the light into the camera. You need this effect, or else the feel of shininess will be lost. In fact, this is actually the most important part when painting metal, so I hope you read this far.
10-12-2006, 01:00 PM
10-12-2006, 01:03 PM
Do more Mr. D! Spread your wisdom wide and far!
05-11-2007, 05:56 PM
Been meaning to post this one for a while.
TAKE IT TO THE EDGE
By which I mean, pay attention to your edges, especially on curved surfaces.
All too often people draw edges like in the lefthand sketch. One edge flows into the next, depriving the shape of a proper fleshed out form. This is fine if it's a piece of paper or cloth or something like that, but all too often you see this kind of mistake on armor, or other thicker materials. When you have a thicker shape, you need to show that thickness, like on the right. Instead of having the top and bottom line meet directly, put space between them and a line to define the contour of the edge itself should be the one to meet the top edge rather than the bottom edge line.
And this can be taken further of course. Once you draw this way you can vary line weight and shape to change the feel of that edge. It can be hard, it can be rough, it can be smooth, it can be a complex machined shape, or it can be an edge which goes from smooth to hard or vice versa, etc.
But if you draw it like on the left then you can't draw that kind of detail in. Works, and can be pulled off just fine with style, but it doesn't have the visual impact of a nice fleshed out form.
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