Hi, I have just started using blender to build models for stage lighting, and I want to create the models of stages and sets from paper drawings. I know how to get the dimensions up using the ‘n’ key, but I can’t get the dimensions to come out right.
As an example, I add in a plane and type in the X,Y dimensions- everything is fine but then when I extrude it and try to set the Z dimension directly, there seems to be no relationship between the size of the object and the number in th ebox.
Also, if I then add a new plane at right angles, it seems to be at a different scale to the first one.
I think you are missing something on how Blender works.
When you are in edit mode, you are changeing the data of an object. The coords of the verts are relative to the object’s center point. There is no (real) limit on how far from the center a vert can be. When you “extrude” like you said, you must have been in editmode. Odds are that you did not extrude exactly 1 unit. ( You can, however, use N in edit mode too, to set the exact coords of a vert relative to the object’s center.)
When you are in Object mode (out of editmode) you are scaling the objects “instance”. It multiplies the relative distances of the object’s vertex data by the appropriate scale factor.
So, if you add new plane, then edit a vert so that the next vert is 3 units away, the scale in that direction is still 1. If you then set that direction’s scale to 2, the verts are now 6 units apart.
This come in handy when you have several objects sharing the same mesh data (copy with ALT-D). They all have the same vertex data, but can be different sizes, because they each have their own scale factors.
The best way to get moderately accurate sizes is to set a convienient scale for the grid (say 1 grid = 6") and eyeball it. If you need it much more accurate than that, you really need to enter the data in a CAD program, then export/import a DXF. Blender is an artist’s tool, not an engineer’s tool.
Thanks for those hints. I am happy with the difference between edit and non-edit mode and I have been happily switching between the two. I am still mystified by the way two planes can come out at different apparent sizes on the screen even though I enter them at the same literal size. Does the view window have some strange effect on scale so that it is modified even though I don’t set it myself? The effect happens inconsistently and (although I have not kept track) I think it has to do with switching between views.
The accuracy I need is not very high, all I need is consistency!
The unit measurements should be consistent, as long as you’ve followed rwenzlaff’s advice.
Are you using different 3Dwindows for the views?
If so, are the Grid settings the same in each?
Shift_F7 (3DWindow settings)
Shift_F5 (to return to the 3DWindow)
Perhaps you could post the blend file example somewhere for us to look at?