Why is my distance in an isometric off

Rhino Rhino for Windows
1

Hi,

I’m using Rhino 5.0. I just drew a 100’ x 100’ x 100’ cube, and then used the Rhino 5.0 isometric tool bar. I then did the 2draw command and I thought the drawing would be 100x100x100. Instead the 2d draw spit out a 81’-7.75" cube. Easy enough to scale up but I was wondering why the drawing isn’t a true 100x100x100. Am I missing something? FYI, I did not rotate the drawing at all, just zoomed in a little…either way the 81’-7.75" comes out. Any insight would be grateful.

JJP

2

Checking it, thanks…

-Pascal

3

Yeah… so, this is not exactly designed behavior; it is more of a somewhat misnamed command. The tool sets a parallel view in the correct place but does none of the required distortion of the objects to make the lengths work out correctly. It looks like the scale factor is 1.22474 BUT if you measure, you need to set the CPlane to View, Project OSnaps to the cplane, and use Distance, not Length.

-Pascal

4

Thanks for the quick reply. As I’m cranking out many of these diagrams scale factor will keep the workflow going. Good info. Take care.

5

HI aztec

try the below Python Script:

#-*- encoding: utf-8 -*-
# Script per disegnare assonometrie isometriche
" write by  Ing.  Vittorio Carlotto  carlottovittorio@alice.it 12-6-2011"
# si usa il metodo XformChangeBasis2 e TransformObject
import rhinoscriptsyntax as rs
import math

strview=rs.CurrentView()
arrplane=rs.ViewCPlane()
plane =rs.WorldXYPlane()
cob2=rs.XformChangeBasis2((math.cos(math.pi/6),0.5,0.5),(-math.cos(math.pi/6),0.5,0.5),(0,0,1), 
                          (1,0,0),(0,1,0),(0,0,1))
objs=rs.GetObjects("get objects",False)
if objs !=None:
    rs.EnableRedraw(False)
    nobjs=rs.TransformObjects(objs,cob2,True)
    rs.Command("_SetView _World _Front",False)    
    rs.UnselectAllObjects()    
    rs.EnableRedraw(True)

Ciao Vittorio

6

Hello Vittorio,
This script is very cool but the geometry it creates is still not the same exact scale/distance. For example I had a 2’x 2’ x 2.5’ cube that when run thru the script was 2.24’ x 2.80’ Let me know if you have a solution or another script that does this to the exact dimentions.
Thanks,
James