AutoCAD

Circles and Lines: From 3D to 2D

8 Dec, 2006 By: Lynn Allen

Create 2D section views from 3D models with SectionPlane.


All this fabulous 3D is great; it's more rewarding, it's more visual, but let's face it -- we get paid to create 2D drawings. So although the 3D models are good at getting our design intent across, we still need to produce those flat 2D drawings with all the different drawing views, dimensions, section views and the like.

One of the biggest chores for a designer is creating section views. Getting the correct display, hatch pattern, linetypes and such can be very time-consuming. I have good news for those of you brave enough to create your models in 3D -- the new tool SectionPlane will do a good portion of this work for you. The concept is simple -- you use this new command to create a section plane that slices through an object and AutoCAD generates the correct section view for you, complete with varying linetypes and hatching. The end result is in the form of a block -- but you can update it should the part be redesigned or if your section plane must be changed. You need a jogged section line? No problem. This new command permits jogged sectioning as well. Let's take a look.

SectionPlane Explained
First of all, you must be in model space, because SectionPlane won't work in paper space. We'll start by creating a section object (yes, this is a new object type as well) by selecting a face. A section plane is created on the face you select. Select this new section plane (to turn, use its grips) and move the section plane to the desired location, as seen below. Find the option to display the cutaway geometry in the shortcut menu.

figure
Use the face option in the SectionPlane command to easily section your 3D model.

figure
The shortcut menu contains all the options you need to control your section planes.

When you use a face to determine a section plane, Live Sectioning automatically turns on. This lets you see the cutaway geometry as you move the section plane around. You could, for example, see the inside parts of an engine that would be difficult or impossible to see from the outside. You can turn Live Sectioning on or off at will, but you can only have one section live at a time if you have more than one section plane. To activate and deactivate Live Sectioning, simply select the section plane object and right-click on the section line. This brings up the shortcut menu.

You have complete control over the color, transparency and other aspects of the cutaway geometry in the Section Settings dialog box.

figure
Here you'll see that my cutaway geometry is red, with a medium transparency of 50%. Feel free to manipulate this to your liking.

If you don't have a face in the plane of the desired section plane, you can also draw your own section line from two points. After selecting the first point, a section representation displays, making it easy to select the second point.

Create a jogged section plane by using the Draw option in the SectionPlane command. Similar to the two-point option, you continue to select points until the jog is to your liking. Because the section line contains grips, it's fairly easy to modify your section after the fact.

Command: sectionplane

Select face or any point to locate section line or [Draw section/Orthographic]: d

It's sometimes easier to draw a section plane first and then add a jog to the existing section plane. To do this, choose the Add jog to section option in the shortcut menu. Once again, you can use the grips to move the jog to its proper location, as seen below.

figure
Use the grips on the section line to control the section plane.

And last but not least, here's the very simple Orthographic option. This makes a section object that aligns to the orthographic orientation of the UCS.

Command: SECTIONPLANE
Select face or any point to locate section line or [Draw section/Orthographic]:
O
Align section to: [Front/bAck/Top/Bottom/Left/Right] :

Create Section View
All of these section lines are cool, but you need to create an actual section view. To begin, return to the Section Settings dialog box to set up the final section view.

Activate the 2D section button at the top of the dialog box, as seen below. Then it's simply a matter of setting up the hatch pattern you want the section view to use, as well as the linetypes and lineweights. If you plan on doing a 3D isometric section view, do the same. If you plan on using the same settings for all your section views, be sure to select this option at the bottom of the dialog box so you don't have to go through the setup process again.

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Use the Section Settings dialog to set your section view settings to your company standards.

There are a zillion different customization settings available to ensure you get the exact results you're after. It would take several columns to touch on them all, so I suggest you resort to the Help menu for an explanation of all the various options -- really, give it a try!

Create a Section
Now you're ready to create your section! Select Generate 2D/3D section from the Shortcut menu. The dialog box prompts you to select the objects to include in your section view. Your section view inserts as a block, using the standard block options such as insertion point, scale and rotation angle.

figure
Create a section view block after setting up the section line.

You can insert this block of your shiny new section view into any viewport in paper space. If your model changes in any way (or should I say "when" it changes), you can update the block by repeating the last step, except select the destination as Replace existing block option. You'll also find that you can create a 3D section view by following the same steps.

figure
The finished section view is in the form of a block.

Give the new SectionPlane command a try -- you just might find yourself with a little extra free time on your hands! It's always so much better when you can get AutoCAD to do the work for you, isn't it?

Until next month ... happy AutoCADing!


AutoCAD Tips!

Lynn Allen

Autodesk Technical Evangelist Lynn Allen guides you through a different AutoCAD feature in every edition of her popular "Circles and Lines" tutorial series. For even more AutoCAD how-to, check out Lynn's quick tips in the Cadalyst Video Gallery. Subscribe to Cadalyst's free Tips & Tools Weekly e-newsletter and we'll notify you every time a new video tip is published. All exclusively from Cadalyst!
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