How to best convey a rounded corners for pseudo-depth in Illustrator?

Question

I want to create a piece of wood. Think of a 2x4 with some pseudo-depth.

Using Illustrator I create the simple appearance of depth using two objects — a light and dark object. The dark object is adjusted so the sides are at opposing angles creating a pseudo-3d appearance. Simple enough. A basic box viewed from the front with fake depth.

I then want to visually convey that corners of this box are rounded. This is easy for exterior corners. But not for the interior corner between the shapes. I want to convey that this corner is also rounded. I want to try and keep object complexity relatively low.. standard gradient fills are okay overall, but I'm purposefully avoiding things like Gradient Meshes.

I'm seeking any methods, practices, tricks or tips for how to accomplish this appearance.

Simply rounding the corners creates an undesired gap, which is fully expected.

So what options are feasible to better create this rounded interior (?) corner?

I could create an additional object behind these 2 shapes and use a mid-tone color.. This seems like it will work but I can never determine what the fill should be... lighter? darker? mid-tone? And I'm not entirely certain it conveys the rounding to others as it does to me.

Or I could adjust one of the shapes to compensate for the gap...

The last two options seem workable as well. But neither of these "feels" correct to me - and never has. This method always "feels" like an actual joint between two separate pieces of wood.

I'm missing something.

So.. how does one convey that this interior corner is rounded using simple fills without a bunch of gradients or meshes?

Answer 1

How about just rouding the corners of the front face and aligning the angled top and bottom of the rear shape to the tangents of the front shape's corners?

This is how I'd expect a piece of timber to be shaped (that is, I don't thing the corners of the front face would curve back along the piece).

I also curved the back corners (by replicating the front face and scaling down, then joining the two faces with tangents to their outer corners) as this would be correct if the whole peice shared the same profile.

Answer 2

First of all, if you do not want unnecessary gradients, let me ditch the gradient you already have (A). This gradient adds unnecessary complexity. I'll comment on this later.

Let me approach this using two concepts.

I. Shape defines Shape

So we are assuming the block has some bevels. In this first case, the shape will define the boundaries of this bevel, the shape.

I am adding a simple shape (C), that can be put behind the other two (D). But one important thing is to reflect that these corners of the block are actually rounded, so we need to make the curve congruent with the other two shapes, so the vectors should align with them (E). Now we have the result (F).

But this solution only implies the corners are rounded, not the edges. So we need to actually define another color or zone between the two flat faces, so we make this gap (G). One problem I will not address is the possibility that the diagram would need to reflect that we have a bevel on the other sides (H).

II. Shading defines shape

A flat design could be a stylistic choice. But if it needs to describe a more realistic object, we need shading.

Shading for this case necessarily uses gradients.

We can add one gradient (I) and we have a rounded edge (J).

But again, depending on the simplification level we need, this could be enough or not.

If we need to only imply that the vertices are also rounded, we could add a stylistic element like a glossy reflection (K)(L).

or we need to start using... a bunch of gradients or meshes. Yea. A more detailed illustration needs them. But it all depends on the style we need.

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A simple method

But actually, if we use the concept of "bevel for all (H)" it is easier.

Let's start with the simple elements (D)

Separate them, duplicate the faces and make them smaller.

Change the color of the big one to the color used on the center piece. Use the blend tool and voilá.

Yes, it can be furder detailed... using gradients and more meshes. :)

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*About the gradient (A), it is not a stylistic gradient, it implies a light-shadow shaping, saying that the front face is not actually a flat face, but a curved one.

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Edition like one hundred

Ok, you want the hard way... :)

First. Making a gradient look like a continuous shape is really hard, and we need to blame your brain...

Here are two gradients (T), and some curves representing a simplification of what the gradients should look like.

The Upper gradient is a continuous one, and the bottom is a gradient coming to a halt on a color for a moment, and then continuing the gradient.

(U) Represents the upper gradient and (V) the bottom. But our eyes start compensating shades, and see (W)

That means, if you do not do that perfectly you will notice that.

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A Not that simple method

So. Rounded bevels on a cube or cuboid can be interpreted as sections of a sphere connected. That is how you could do that in a 3D modeling software.

Then, take a sphere (1) that is easily shaded to look like one. And divide it in 4 (2) (for nos as an example I am using a square grid) Now you have your vertices rounded (3). Now connect them with a rectangle using the exact same color values as the sections of the sphere. I used a mesh there so I have different nodes with specific colors.

I am lazy and only did 1 section as proof of concept.

But as you have perspective... you need to apply that to the vertices.

Now you have a perfect gradient for the corners... now you have to connect them. There is not an easy way to make those transitions.

This method at least answer very precisely your questions

I can never determine what the fill should be... lighter? darker? mid-tone?

Use a color picker on the zone that mimics the angle you want. That will give you more consistent colors on light and shade.

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Or use 3D software and make a stylized render...

Answer 3

What about something like this? There's an extra shape behind, filled a colour which is kind of half way between the light and dark shapes, and a gap between the light and dark shapes to form a kind of bevel all the way down.

Maybe even more of a gap and some slight rounding to fix the corner at the bottom

Answer 4

Much text and images has already been sown. The accepted answer presents a piece of planed plank with rounded edges, which is a common timber material. Probably just that was actually hovered in OP's thoughts, but the original (unedited) question asks how to draw a box which has otherwise sharp edges, only the corners are rounded.

If the corners are rounded to spherical they cannot be tangential with the planar surfaces. The rounded area has still sharp edges and one can draw them by inserting curved pieces to the corners. OP has already presented one such corner as an example. https://i.sstatic.net/IxkCd.png The idea seemingly wasn't fully satisfactory, so the question was written.

If the rounded area meets the planar surfaces tangentially, the case becomes interesting. The limitation "only simple fills, no complex gradients" makes an exact image impossible. A rendered 3D model (grey) in the next image shows such box:

Tracing the rendered greyscale version manually (to keep it simple) is easy, but the corner implants should have complex gradient fills or equivalent blurs or blends to fade the seams. Otherwise there's a non-tangential bevel.

In the right the corner implants are divided to 2 parts which have solid colors. They resemble a little more tangential roundings than single color implants, but essentially this is the roughest possible approximation of using gradient fills. Only the context where the image is used can create an impression of no-bevel tangency. If the image alone should do the job the problem is unsolvable without proper (complex) gradients.