Hi,
This is a fairly simple one I imagine. I would access the knowledge database but it doesn’t seem to be working for me at the moment.
I want to be able to make the diamater of a circle or cylinder the same width (for example) as that of a cube. How do I do that?
Is there a place where these figures are kept?
Well if you select your object and press “N” it will bring up a dialog box that lists all kinds of info like size and location etc… 
Well,
there isn’t any simple way since the data that the Nkey reveal has no absolute meaning. For example if you create a circle in the default grid size setting of 1.00 (check it in the shift+F7 window, shift+F5 to come back to the 3D window) and then press ‘n’ you’d get 1.00 for each sizeX, Y and Z. Now set the grid to something else, 0.25 for example. Create another circle and presse ‘n’ : you’ll get the same values for size X, Y and Z of 1.00 and yet that second circle has a diameter of only one fourth that of the first !
Coming from a CAD background like I did that’s simply pissing.
The complications don’t stop there but it no use to get into that.
I made for myself a whole set of primitives that are one blender unit big (diameters, side for cubes and squares). I take great care to change the size only through the nkey and if I ever lose track, like sometimes it is unavoidable, at least could I use the blender unit as a reference point. The blender models, when imported in AutoCAD through DXF, have a scale of one inch per blender unit.
What you can do is create a Cube with the size value of one. Create a Circle with the size value of .71. This is not exact, but you can only change the size value to the 100th decimal. I JUST found that out. Was trying to go for .705 ! Anyway…you can select the four outermost vertices where the Circle touches the Cube and use the Shift-S function to snap the selected vertices to the grid ( assuming that you created the Circle in the same spot as the Cube). This is not a perfect Circle…but for all practical purposes it should suffice. Maybe if you explained the reason why you wanted suh precision…I could help more.
By the way…have you ever used Rhino 3d ? Has much better snap functions and you can always convert to dxf and use that in Blender.
This is not quite exact : while Blender’s display is rounded off to the hundreds it still take into account a much much greater precision, although I can’t tell it’s limit. Anyway, there a difference between a circle scaled at 0.707 107 and another scaled at 0.707 106 781.
One can verify this by creating three identical circles in top view and first scaling one at .71 on the x axis, the second one at .707 107 and the last at .707 106 781. Reset the values of size X with ctrl+a applied to each and then scale up a big amount, like 1000 in all axes the circumference on the X axis will be quite different for each circle while indentical on the y axis which wasn’t first scaled to test precision for control of the experiment.
I’m a bit confused. Wouldn’t sizes be fundamentally important to modelling?
What I am trying to do is quite simple: I want to fuse a cylinder and a cube together, but the diameter of the cylinder has to be the same size as the width of the cube.
Are we saying that there is no perfectly accurate way of doing this in Blender?
It all depends : the relationship between modelling in Blender and other softs like Rhino or AutoCAD is much like that of free hand drawing is to drafting.
What I am trying to do is quite simple: I want to fuse a cylinder and a cube together, but the diameter of the cylinder has to be the same size as the width of the cube.
Are we saying that there is no perfectly accurate way of doing this in Blender?
Anyway we do it, anyhow we think it works there is no total accuracy in computer graphics no matter what program were talking about. But one can manage to get very, very close to it, so much that the difference doesn’t matter.
I have a file where I store all my primitives based on the Blender unit on layer 20 ; it also shows a square and a circle that seem to match perfectly the way you’re trying to achieve even at the highest zoom in.
I could send it to you if you want it.
Nah, that’s OK. Thanks for offering. I managed to get something close to what I was looking for…and that will be good enough.
At the moment, I’m also having problems using the intersect just to cut a circular hole out of a cube. And I can’t seem to make faces out of circular edges either.
Is it achieving the most simple things that is difficult in Blender or am I just missing something?
Caleb, I think you are getting yourself entangled in a web of perfection here, mainly because you want to do it from the numbers point of view. I might be wrong but I think there is a way to do it from the available tools point of view. Select your cube and hit ‘center new’ in edit buttons. Do the same for your circle or cyl. Now they each have their center point exactly central. Shift-S and hit Curs-> Sel. That puts the cursor on the center of the circle (it’s still selected).Select the cube then Shift-S and hit Sel-> Cur. Now both central points are overlapping and both objects too. Now if both objects have enough subdivision you should be able to zoom in and see the vertices touch one another as you scale one object to fit the other.
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Had to try it. Simple solution. Create a Cube with size of 1. Create a UVSphere, also size one (32 segments, 32 ring default). The eighth ring from the “top” of the Sphere matches the Cube as exactly as you can get in Blender.
Intersect ? That would mean that you are using a version that doesn’t have booleans. Use 2.25 : that work better. You may have to use ‘remove doubles’ and the decimator afterward.
Myself, I’d rather construct the intended result most of the time.
I have version 2.25 and it says intersect. Am I doing something wrong?
Oh I see the Boolean using “W”.
I find the Boolean functions (Intersect - whatever) a bit unsatisfactory actually. It just never works the way I think it is going to.
I’m sure it’s just a case of getting used to it.
Oh well. I just scrapped another piece of work because I think I’ve taken the wrong tack…again. sigh
I’ve started with AutoCAD, then MAX, then Blender : got used to dead end during apprenticeship so much !
It gets much better with time though.
Have a nice day.
With NKEY you get the size of the object, not of the mesh! If you scale your mesh in editmode, the object still has size 1. But if you TAB out of edit mode and scale your object, you get the exact size with NKEY.