Slow Down and Render This

Yesterday, I received an email with an attached drawing. Verbally, the request was to determine why the drawing is so slow, especially when using the zoom extents.The email included the following additional information:

This file was messing up badly on Wednesday...crazy slow, etc.

This morning with my new reload of AutoCAD 2011, it wasn't as bad... but still has signs of corruption...

One thing that I noticed is that the TIN in the V-TINN-VIEW layer doesn't look right... the contours are fine... but I didn't know if you had a fix for that...

There are lots of things that can cause a drawing to be a little slow. I have a list of things I check in a drawing but I knew that many of those had already been checked by the owner of this drawing. The comment about the TIN not looking correct was definitely a clue to the problem as was the knowledge that the user had recently been working with point clouds including some third party software.

I knew the fresh install and absence of the third party software had ruled out that being the issue so my first option was simply to open the drawing. Here's what I saw in the bottom left corner of the application:

This is not the ucs icon that I typically see in my drawings. The thickness of the ucs icon elements was an indication to me that the visual style was set to something other than 2D Wireframe.

To verify my suspicion, on the View ribbon tab, I selected the dropdown on the Views Panel and found the visual style was set to Hidden.

 I left clicked on the Hidden visual style and changed the visual style to 2D Wireframe.

Now the ucs icon looks as expected and the speed of the drawing has returned to "normal".

Now if you are using AutoCAD 2012 or later, take a look at the upper left corner of model space. There you should find the Visual Style Controls.

As you can see, the visual style in this drawing is now set to 2D Wireframe. Changing this setting from Hidden to 2D Wireframe greatly improved the speed of the drawing.