Oblique Elevation Drawing?

Hello,

I have been creating axonometric drawings using the shear command to great effect; however, now I wish to create an oblique elevation projection. I can draw this easily, but since my geometry is a bit too complicated to draw quickly. I have downloaded AxonOblique, which works for simpler geometry. I know this has been asked about in forums but I wonder if there is a way to set up the camera to create these receding lines.

Thank you,
Erik

I went through this with a couple of student requests last semester. The following is the way I finally ended up “faking it”:

  1. Decide on a common base point for the following operations - preferably one that lies on the front face of the object.

  2. From the Top view, scale 1D along the Y axis using the basepoint above as origin and a factor of “1 divided by the square root of 3” (~0.57735) This is necessary if you want the drawing to have true dimensions along the diagonal. For a more realistic effect, a smaller scale factor might be appropriate, the classic “cabinet oblique” style drawing used half the real dimension on the diagonal, so half of the scale factor above.

  3. From the Right view, Shear the model +45 deg. (CW) using the basepoint as origin and a horizontal line as the axis.

  4. From the Top view again, Shear the model -45 deg. (CCW) using the basepoint as origin and a vertical (Y axis) line as the axis.

  5. Voilà! Now do a Make2D with the Front view…

Obviously the 3D model is completely useless after this operation, so either do this on a copy or Undo back to where you started… I can create a quick vid tutorial if you need later.

Edit - it occurs to me that one might be able to set this up as a series of components in Grasshopper, so you could just plug the model into it, bake the result, then Make2D…

HTH, --Mitch

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What is the difference between Oblique VS Isometric projection?

Here is the Isometric projection micro… You might change some numbers to get it right…

! _Select _Pause _SetActiveViewport Top _Rotate 0 30 _SetActiveViewport Right _Shear w0 w0,0,1 -45 _SetActiveViewport Top _Zoom _All _Extents

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1 Like

Hi guys

I tried to edit the isometric projection macro.
What about this ?

! _Select _Pause
_SetActiveViewport Front
_Rotate 0 45
_SetActiveViewport Right
_Shear w0 w0,1,0 45
_SetActiveViewport Front
_Rotate 0 -45
_Zoom _All _Extents

Cheers

This is actually for creating an Axonometric projection (for doing a Make2D or printing), not isometric. It’s from my tutorial here.

For isometric views, you can use the following script (should run on both Mac and PC)…

IsometricView.py (740 Bytes)

–Mitch

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That should work. Here’s a script version, not tested.

Oblique
Function Oblique
  Dim S,P,F,A,B,M
  Call Rhino.Print("Oblique: Uses active c-plane, doesn't make copies")
  S = Rhino.GetObjects("Objects to transform",0,True,True) 
  If IsNull(S) Then Exit Function
  P = Rhino.ViewCPlane()
  A = Rhino.GetReal("Angle (deg)",45) 
  If IsNull(A) Then Exit Function
  F = Rhino.GetReal("Scale factor",1) 
  If IsNull(F) Then Exit Function
  B = Rhino.XformChangeBasis(P,Rhino.WorldXYPlane())
  M = Rhino.XformIdentity()
  M(0,2) = F*Cos(A*Rhino.PI/180)
  M(1,2) = F*Sin(A*Rhino.PI/180)
  Oblique = Rhino.TransformObjects(S,Rhino.XformMultiply(Rhino.XformMultiply(B,M),Rhino.XformInverse(B)))
End Function

Thank you @Helvetosaur and all other contributors.
I have tried your technique at ‘faking’ it and I haven’t been able to make it work properly. In step 1 does the location of the base point matter? In step 3 and 4, what does CW stand for?

I have tried a normal -45 shear in perspective and it seems to give me a result close to what I want. I have attached the files, but I think the elevation should remain flat and planar as a normal elevation would while the rest of the building shears. I wish to try your technique, but I am afraid I am confused by the points I listed above.
Thank you again! I have also attached my failed attempt using your technique.
Thank you very much. Elevation Oblique1 test.pdf (11.9 KB) Elevation1.pdf (10.5 KB) Elevation Test.3dm (4.7 MB) Helvetosaur Technique Test.pdf (12.2 KB)
Erik

FWIW - I was just going to answer that CW is clockwise but instead thought I’d tried the instructions.

Attached are the results - 2 because as far as I know, CW is -45º and CCW is 45º but then you would have to make a 2D from the BACK view. As base point, I picked a point on the right edge of the sloping wall where it meets the roof - not visible from the back view.

Oblique2-back-cw-ccw.pdf (5.6 KB)
Oblique2-front-ccw-cw.pdf (7.3 KB)

Hi Thomas

AFAIK, it works and looks like the result has to be seen from Z-.

My attempt tries to follow what Mitch posted and gives a result to be used from Y-

That’s good, Erik has one more option to try.

Thanks

Yes, CW is clockwise (-45 deg.) and CCW is counterclockwise (+45 deg). See if this quick video helps, I used a wireframe bounding box on the object to help establish and keep a reference point, which I later deleted.

The “correct” view for the result is the Front view, so I used Make2D with “current view” from that. For me, oblique views are sheared elevations, thus Front view seems the most logical. The Make2D result is of course placed in the top view.

HTH, --Mitch

Hello Mitch and Wim. I greatly appreciate the help you given to me with the process you have created to make this projection. Also @ helvetosaur - how nice it was to make a video! It was very informative. BTW what software is that? the full version of camtasia or the snagit?

Thank you to all who have helped me once more!
Best,
Erik

No, it’s Jing - free. I also have a full version of Camtasia (same maker - Techsmith), but I only drag that out for more involved projects.

–Mitch

Unless I screwed up something, it should use the current c-plane, not a fixed one, but may need a factor of -1 somewhere, i.e.
M(0,2) = - FCos(…
M(1,2) = - F
Sin(…
or enter -1 as scale factor.

Ah, OK, I must have run it with WorldXY CPlane …
Thanks

Hi Mitch I am also trying to make an elevation oblique.
I have managed to do step 2, rescale 1D along the Y to get approximately the right measurements
I managed to do step 3. and shear horizontally.
However I am unable to shear vertically. Why might that be? Is there another way to do it without the shear command? In the command line of shear I am not able to make a vertical line as the axis.