Transitioning from 2D to 3D AutoCAD drawings 114

In my last “Transitioning from 2D to 3D” post, I finished creating the 3D VAV boxes in the HVAC plan. The VAV boxes are currently on the floor. I could move them to the ceiling now, but I decided to wait until I finish creating the ductwork so that I can move the ducts and VAV boxes at the same time.

The ductwork provides the opportunity to use a variety of AutoCAD tools. As usual, there are many different ways to create the same model. I’m going to focus on the methods that enable you to take advantage of the existing 2D geometry using the fewest steps and/or the least amount of thinking.

1. Zoom into an area with ductwork.
   
2. From the Dashboard, choose Cylinder.
3. Pick the midpoint and endpoint of the existing 2D duct to specify the radius of the cylinder. Don’t worry that the cylinder is oriented incorrectly.
4. Drag down a small distance and pick to set the height of the cylinder. You could just as easily drag up. We’ll rotate the cylinder into the proper position and then adjust its height by snapping to existing 2D geometry.
   
5. Select the cylinder and then pass your cursor over the Move grip at the cylinder base. The Move grip tool will display.
6. Select the axis around which you want to rotate. By default, AutoCAD will try to move the selected object along the axis but you can easily switch to Rotate functionality.
   
7. Press the spacebar twice to change from the Move grip tool to the Rotate grip tool.
8. Drag the cursor straight up (along the z polar axis) and pick or enter an angle of 90. If you drew the initial cylinder (step 4) up instead of down, you would do the opposite for this step.
   
9. Select the stretch grip at the end of the cylinder and stretch it to the proper height. The “proper height” depends on what your goal is for the model. If you want the model to be as close to real life as possible, you might want to create each duct segment, including the connectors, as separate objects. However, if you are only concerned with how the model looks, you can reduce steps by combining several “parts” into one. I decided to stretch the duct all the way to center of the large duct to which it will connect. It doesn’t exactly match the real-world parts, but it is quick and will “look” fine after I create the larger duct.
10. Pick the midpoint of the line at the end of the large duct.
    
    I could have “eye-balled” a distance that would extend the small cylinder far enough into the larger cylinder, but if I didn’t stretch far enough, there would be a gap at the intersection of the two cylinders. If I stretched too far, the small duct might protrude to the other side of the large one. By stretching to the middle of the larger duct, I know there won’t be any gaps or excess protrusions.

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