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Cel Shading

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I know that cel shading is cartoony-looking images with black outlines, but could someone give me a more detailed description? And how would I go about drawing such an image? Is it faster and easier to draw than a realistic-looking image? Thanx in advance

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Guest Anonymous Poster
cel shading is a process used to render 3D models in a way that they look cartoony.
they are not drawn like good old cartoons, and not all 3D modeling programs support cel shading.

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You know how games nowadays are 3D instead of 2D? They use 3D models, which are created in a 3D modeling program, like 3D Max, then they are given textures and you render them.
Rendering == the software 'draws' the picture, not you.
You make the model, texture the model, add lighting, add a camera for the scene, and tell the program to render it.
I don't have 3D Max, but I do believe there is a plug-in for it to do cell shading.

[edited by - wolfmanyoda on November 21, 2002 10:55:40 PM]

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Any cellshading in max is for its own rendering engine. It won''t do any good for a cell shaded game, unless you''re using it pre-rendered in some way.

It''s pretty much in the coders hands to sort out toon/cel-shading, not the artists. Once it''s coded, then it''s the artists job to optimise their textures to look best, but the actual cel-shading is a feature of the engine.

There is a cheat, if you want celshading in an existing engine, and don''t want to code it in. You simply make your model. Duplicate it, scale it up a little bit, then flip the normals, so they point inwards, and color the whole mesh black. That will give you the black outline.
It doesn''t look as nice as genuine cell shading, and you have no control over the actual shading - merely the outline, but what can you expect? It''s just a cheat.
Note that this will double the polys of your models though.

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It depends on your definition of ''realistic''. Cell shading is simple in concept, and none too difficult to pull off. However theres lots of more advanced techniques you can add to make the whole thing more interesting (accurate ''toon shadows in Jet Set Radio for example).

Neither is ''easier'' since they can both be done to varying amounts depending on what you''re aiming for.

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I have been doing alot of research on this topic, so here goes my two cents. I'll skip the details. The way I have seen it is by way of vertex shaders. What the vertex shader does is get the cosine of the angle between them. This is between 0 and 1, so instead of using this for the texture coordinate, it gets a value from a 1-d texture that has 3 values: near-black, gray, and white. (ex. ) it then combines the color in that position with the color of the vertex. Doing so gives the vertices only 3 different colors, therefore giving the cel-shaded or cartoon effect.

To get the outline, you test the vertices and their neighbors for their normals. If one points away and one points towards you, then they are colored black. This gives the outline. It doesn't work so well on highly detailed objects, because it gives unwanted side effects with both effects.

All you do to use this effect is the same way you would use any other vertex shader, just attach it to the material and D3D takes care of the rest. I don't know about OpenGL or any software programs, e.g. 3DSMax, but that's how it works with vertex shaders. And there are many example vertex shaders and programs to view them, too. Some good examples of many vertex shaders and plugins for 3DS MAX are here.

This style is in a group of "non-photorealistic rendering" which you might have heard of. I'm using these type of effects in my game, and one of the benefits is that the models have to be less detailed in order for the effects to look good.

I hope I didn't confuse you, but that's how I understand it. A good cel-shading article for the theory

It is coming...8 years in the making and It is finally coming...

-Beavt8r


[edited by - Beavt8r on November 24, 2002 1:41:17 PM]

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Actually, u r confusing me. LOL. I''m just a newb. Oh and u kind of answered the question some1 else asked me. What I meant when I asked if cel-shading is easier than realistic-looking, I meant, which one needs less detail and is faster to make. Thanx for ur answer.

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Hehe...sorry....got a little off-topic. Well, if you have the vertex shader and have something to do with the programming, all you have to do is set the vertex shader and it does the rest. But with normal lighting, you just set everything normal. And as I said in the previous post, the models usually don't need much detail, because too much makes the effects look weird. So in a way, cel-shading is a little more difficult, but not by much. A few lines of code is all. Hope THAT helps this time.

It is coming...8 years in the making and It is finally coming...

-Beavt8r


[edited by - Beavt8r on November 24, 2002 1:49:33 PM]

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Well, I don''t mind putting a little more effort into it ONCE as long as it makes the rest easier. So u r saying that if I put a little effort into making it cel-shaded, I don''t have to put in as much detail into my drawings later? Thanx.

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Absolutely. I read somewhere that if there''s too much detail, the way the cartoon effect works (the 3 color levels) then it will look strange. Something to do with the way the outline is calculated or something...but anyway, I''m glad I could help. If you think of anything else, I''ll try to answer because since I''m using "non-photorealistic rendering" in my game, it helps to try to explain it...lets me learn more about it. Good luck!

It is coming...8 years in the making and It is finally coming...

-Beavt8r

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