## Tuesday, July 27, 2010

### Slope Arrow Direction, Source: Autodesk University

I’m quickly approaching 500 posts. Instead of creating new and different posts I’d thought I’d recycle some posts leading up to the 500th post. (Hey! TV shows do it all the time.)

Autodesk University is coming up soon. Here’s one of the tips I discovered when I went. It provided a foundation for a bunch of posts I’ve done since the original publishing of this post.

A coworker was looking for a method to have a slope arrow always point down hill. He saw the method at AU, but couldn't find the handout which had it. I found the method on the AUGI web site. Since I will probably need this in the future, and won't remember that I found it on the AUGI web site, I'm going to post it here in the form of a surface slope label.

The formula to use in the expression is the following:

IF({Surface Slope}<0,0,pi)

Put the expression in the arrow component rotation of the surface slope label, see below:

The value of pi is used because the rotation value is in radians. If you want the arrow to go the opposite way, just reverse the second 0 and pi. Now if you use the label the slope of a surface the arrow will always point in the direction you want, but the slope will be positive or negative. You could always drop the sign of the label, but that would be too easy. Another way to do it would be to add another expression:

IF({Surface Slope}<0,-{Surface Slope},{Surface Slope})