Hi Friends,
Is there any way to set 3D boxes to be a precise size? I'm working on an image where I'm using the 3D Box tool to make a realistic bookcase. I'm trying to make it as close as I can to scale with the bookcase in my living room. I'm rounding everything to the nearest inch or pixel, so it won't be precisely to scale. But it's generally using 1inch = 10 px.

Now I have a case where I need to cut out part of one of the faces of the 3d box, roughly a half inch in from the edges. Here's generally what I mean:

So there's a hole in the bottom of this box. What I need is to make the distance from all the edges equal. While I would like it to be half an inch/5 px, I'll be happy if I can find a way to make them all equal.

In order to do what I have there, I made one 3D box and duplicated it. Then without moving it or the vanishing points, I dragged the sides of the duplicate inward, and the bottom downward. Then I ungrouped the boxes and deleted the unneeded 5 sides of the smaller box. Then I differenced the bottoms. But I can't find a way to make the distance from the edges equal. I'm thinking of setting Guides where I can snap the handles, but I don't know how to set the guides, without doing a lot of math.

If there were a way to set precise sizes for these boxes, I could just make one 10 px smaller, and that would do it. But I'm not sure changing the width and height (using Selection tool) will do exactly that. I've also thought about scaling just the bottom side. But I don't think changing the height and width will scale it in perspective....will it? If I set it to stay in proportion, will it keep the proper perspective? Or will it only keep the original perspective? In this case, close enough is probably ok. But of course I'm always so curious Anyway, that's why I'm thinking it would be better to scale a whole 3D box than to scale one side.

But I can't see a way to scale it precisely. And I don't think there is a way. But I wanted to ask.

Thanks

PS - Oh, maybe the site Maestral found the other day?? I'll check

I`d recommend using the schematics from the same thread, since that way you could use the "brown rectangle" as a template for measurements / kind of a floor plan, so to say. For vertical reference, you should add a vertical reference line from the intersection/touching point of the two rectangles.

Then you could add a few guides aligned with the schematic and draw 3D box along these.

And, yes.. you could also use the Length calculator ,)

You queston really highlights the clever idea that went into the 3D box tool, as well as the problem with using that tool effectively.
the ingenious programmer(s) have used the sstrange-but-true fact that you can establish two VANISHING POINTS and construct right rectangular prisms (boxes) to your heart's content without ever establishing a VIEWPOINT.
The problem is that without a viewpoint there is no way to determine the relative dimensions of any of the line segments used to create your boxes - in other words, you can't determine when boxes are cubes or 'bricks'.
So to have an x inch wide border all the way around your face you first need to establish a viewpoint. Then you can use Maestral's nice diagram as a hint on how to transfer a dimension from your top elevation or 'plan view' to the perspective drawing.

To sum up: without a VIEWPOINT it looks like your perspective drawing has dimension but it doesn't!

Sigh! Ok, thanks guys. I guess it's pretty much what I thought.

Don't get me wrong, I'm not complaining. It's a fun tool, and quite precise by itself. But it can't be used with measurable precision outside of itself.

Anyway, thanks again