Are Illustrator 3D effects not calculating accurate values to construct with

Question

I'm having an interesting issue I recently encountered when dealing with Illustrator 3D effects. I'm trying to explain this issue with a more simple example than it actually was.

I have two isometric left 3D cubes which I already have expanded to their appearance. Let's say these two cubes are two table legs of a desk. They are perfectly isometric left aligned to each other, but I don't know their distance.

Now I want to add the missing tabletop. I don't know how long the length of the tabletop should be so I thought I need to get the distance of those two anchor-points: So I checked transform, got x, y coordinates of both anchors and calculated the distance with an online calculator.

Let's assume the distance between these two points is 240pt. I created a line to doublecheck this and it fitted perfectly from one anchor to the other.

So I created a 2D shape with the exact width of 240pt, applied the same 3D effect as on the cubes, but it turned out: The tabletop was too short. I thought it must have to do with me mixing up some numbers, but I did it again and it did not work.

I wanted to make sure that the way I do the calculation is correct, so I did the exact same thing in Cinema 4D, and it worked. Is Illustrator not actually calculating with proper values? Is it behaving differently when it comes to coordinates and 3D?

Answer 1

No its accurate, in this sense, at least on my machine. But then depends on what you mean by accurate. I can easily show that cinema 4D is not accurate in lots of things.

Based on your description it seems you are in fact calculating the projected distance. Projected distance is not 1:1 proportional to non projected distance*. it is like flattening your 3D view and measuring distances from that (camera loses scale so you need to chose right sized scale to project it).

Image 1: It works perfectly fine.

But, I rarely use this tool. If i want 3D geometry i will use a 3d application for that. If I need vector art I just export my geometry form 3d app into illustrator. Or then draw by hand to keep up my practice. Example of the former and a example of the later

PS: you can measure distances with the line tool

* Its possible to make a isometric cardinal axis be, but illustrator chooses to foreshorten instead of keep length, this is perfectly valid if not really practical. Nothing says post camera scaling is not possible.

Answer 2

Select all areas 2d ago and the data groups and the command Extrude.