visual art The dynamics of cel shading

[Kel_Grym 1,917]

I'm working on a piece of art where I'm having a tough time with cel shading.

 

No, I can't show you.

 

Pls, Don't ask. Trust me.

 

My main problem is understanding how certain lighting angles work with cel shading. I've looked at many artists and seen many variations of cel shading styles, however it seems that i'm only capable of doing the simplest of things.

 

Anything too complicated and it turns to shit.

 

Pls...amazing cel shading artists....

 

Tell me your secrets.

 

 

[Bucky McGillyCuddy 956]

Are you doing actual 3D work you want to get a cell shaded look on instead of soft realistic soft shadows or are you doing 2D drawing that you want to simulate the cel shading effect?

 

It's a little hard to help without an example but I wont press you for one. No one will crucify you for not being able to draw physically accurate shadows. I always say subtlety is important with lighting unless you need the shadows to really give a scene a particular effect.

 

Reference is key and practice practice practice. 

[Kel_Grym 1,917]

@@Bucky McGillyCuddy,

 

2d work.

 

Reference is important, but it seems with the particular combination of figure placement and lighting, I can't find an appropriate reference.

 

I could say screw it and go with a different lighting or minimal cel shading, but I'm trying to do something advanced.

[SasQ 1,376]

The actual cel shading algorithm is actually a version of tangent shading. It is based on the idea that when you look at the face of some 3D object at the angle roughly perpendicular, you see a flat area of color. But when you look at the same area at a very narrow angle, almost tangent to the surface, it appears as the edge of the object. In cartoons, such an edge is being drawn as contour line, usually black, or dark version of the face's color. The simplest approach is two-state: Either you look at the edge (tangent ray) and you see the outline, or you look at the face (perpendicular angle) and you see the solid-color area of the face (fill). To achieve shading, just add some intermediate steps between 0° and 90° with gradually changing brightness. (But not too much, if you don't want it to look too much realistic.) In 3D graphics rendering, it is usually done by using a texture with a step-wise color gradient (just several stripes of solid color), and using the normal vectors of surfaces to find out the angle at which the particular surface is being observed, and then mapping the angle (using a dot-product of the ray with the normal vector) into a particular point on that texture.

Edited November 5, 2014 by SasQ

[Kel_Grym 1,917]

@@SasQ,

 

That is informative, however a wee bit too technical for me to digest and practically apply.

 

I work intuitively from reference, though some of the things I'm trying to do aren't really in my references.

 

However, I will show one of my cel shaded works. [incomplete -- very simple]

 

 

Don't laugh at my orange guy.

 

He's tough and will beat you up.

 

One of my issues in the other thing that I'm working on is casting hard shadows from direct lighting. I this leg that casts a hard shadow on another figure, but it makes the figure look way too flat.

 

Maybe its my layer order, or just not planning ahead better, I dunno.

 

While I can't show that picture, maybe there are some things that could be worked with on my orange guy that'll help me understand how some of light angles work better.

[SasQ 1,376]

 

 

That is informative, however a wee bit too technical for me to digest and practically apply.

 

Oh.. OK, I'll try somewhat simpler:

 

 

Imagine rays of light linking the eye with different points on the surface of some 3D object (here a sphere, for simplicity). Such a ray can touch the surface at different angles. Imagine that at each point on the surface there's a little "needle" sticking out of it (blue ones in the picture) called normal vector. These normal vectors, or "normals" in short, point at the direction exactly perpendicular to the surface. When your line of sight is aligned with this vector, you're looking straight at the surface and you see its "flat" color. But if the ray of light is perpendicular to the normal vector, this means that it is parallel to the surface, and it just smidges it, touching it, but not being stoped by it. Such a line is called "tangent", because it just touches the surface from the side. The point where it touches the surface, is a point on the edge, where it changes from being front-side to you, into being back-side to you. Everything up to this point is visible and appears flat (solid fill color), and everything which is beyond that point is back-side to you and invisible, so the point of tangency is the edge between visible and invisible, and there you would see a contour line in cartoons.

 

It's interesting that although cartoon animators work in 2D, they need to actually visualize their characters as if they were 3D objects, to figure out where they should draw contour lines.

 

 

 

Don't laugh at my orange guy.

 

 

Why should I laugh? It looks quite OK. I would only match up his hand with his head a bit more, because his head is made of crude straight lines, and his hand looks more softer, since it's made of curved lines. Straight lines doesn't look very good in graphics, because they look very sharp and artificial (unless that's how you want them to look like and you use it for artistic effect).

 

 

 

One of my issues in the other thing that I'm working on is casting hard shadows from direct lighting. I this leg that casts a hard shadow on another figure, but it makes the figure look way too flat.

 

 

It might be that your lighting doesn't match up. For example, you did very well with the shadows on his face. If you cover the rest of this image, they look OK. But when you uncover it, they look odd, because the lighting isn't reflected at other parts of his body, so they seem flatter or detached, as if they were in another dimension where this lighting doesn't reach them. Try to imagine where the rays of light and shadow go, from what directions, and match them up everywhere on your image. If you light his face from one side, try to light the rest of his body from the same direction.