Loft object orientation angle - How to rotate cross section

Loft object orientation angle - How to rotate cross section

truckexpert
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Loft object orientation angle - How to rotate cross section

truckexpert
Advocate
Advocate

I am trying to create a guard rail using loft (open for alternate method). It seems pretty easy, but the rotation of the cross-section and orientation seems impossible to control. Attached is a simple model of what I'm trying to do, and what MAX keeps doing "wrong." How do I make the guard rail be vertical, and follow the terrain as shown?

 

Any help is greatly appreciated!

Dave

2025-01-09_11-05-20.PNG

Peace,
Dave

System Information:
------------------------------
3DS Max 2023 and 2024
Microsoft Windows 11 Pro
Dell Precision 5820
Intel(R) Core(TM) i9-10920X CPU @ 3.50GHz, 3504 Mhz, 12 Core(s), 24 Logical Processor(s)
Display Adapter: NVIDIA RTX A4000
Adapter RAM (1,048,576) bytes
Installed Physical Memory (RAM) 64.0 GB
Total Physical Memory 63.7 GB
Available Physical Memory 45.6 GB
Total Virtual Memory 81.7 GB
Available Virtual Memory 56.5 GB
Page File Space 18.0 GB
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Message 2 of 4

MartinBeh
Advisor
Advisor

Loft is really old code, and rather annoying in how it deals with transformations...

 

For starters: Are the cross sections changing at all, or do you simply want to use them for their orientation?

Maybe the Sweep modifier on your path with one of the shapes as Custom Section is useful?

 

Also note that with Loft, you can either start with a path and then use "Get Shape", or you start with a shape and then use "Get Path" - I often found the latter to be more predictable. And once a Loft is created, you can go into sub-object mode to access the Shapes and adjust them.

 

Creating all splines (path and cross sections) in the same viewport to make sure their local coordinate systems are aligned might also help.

 

NB: You can create meshes just from cross sections - for that you create and place as many cross sections as you want (e.g. by placing them along a path) and then attach them all into one shape; add a CrossSection modifier and a Surface modifier and finish with a Smooth modifier (or some other modifier to fix the surface normals). 

Martin B   EESignature
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Message 3 of 4

casey_hawley
Advocate
Advocate
Accepted solution

Rules for Sweeps/Lofts:

  1. Draw the path in Top view. Always. (If it's supposed to run vertically, rotate it up afterward.)
  2. Draw the profile in Front view. Always. (The profile will always run along its own LOCAL Z axis.)

Here is an example of a curb w/ gutter profile in LOCAL Front view. Notice the Z axis.

casey_hawley_0-1743033066201.png

 

And here it is in WORLD Front view:

casey_hawley_1-1743033333137.png

 

Don't you f*ing hate how the axes change between LOCAL and WORLD? I guess you could also say the profile will always run along its WORLD Y axis as well, but I learned about and think of Z as depth from the camera (of course) making it easier to remember, personally.

 

Memorize and follow these rules (or take time to methodically test and make your own rules), otherwise you will constantly be confused by how they turn out (well, I was at least lol) and then waste time rotating shapes, rotating pivots, or trying every setting to get lucky. This way is simpler and easier to remember for beginners, IMO.

 

Message 4 of 4

ads_czechoj
Autodesk
Autodesk

Hi Truckexpert, you need to follow the steps provided by Casey.

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