How to set dynamic block visibility based on an input value

[Anonymous]

I want to create a duct with a bellmouth vent at the end.  The block has the ellipses change based on the angle of view input.  So lets say the duct is viewed at a 45 angle and then at a -45 angle.  The hidden lines will change from the front to the back.  I'd like to have the user change the angle and have the hidden lines switch from hidden to viewed based on the user angle.  I could have 2 versions of this block but I'm looking to see what I can do cause I've got a bunch of other reasons and situations but they'd be more difficult to explain. 

[Charles_Shade]

The use of Double Lookups can allow for Vis States to change based on say a Flip Action.

I would think there is an option to do that regarding your DynBlk. 

The best thing to do would be to post a simple example to ask questions of.

You can also have the Flip occur based on a range of angles so you may not be limited to left and right (i.e. 0 and 180 or in your case 45 and -45)

ojuris did this in a block. It is attached here. Look at the Block with ELEV.

You can also search this Forum Board for Double Lookups and find many threads related to this funtionality