Auto Contact Pen Scale to Proximity Factor

[srwopschall]

Replicate the use of the auto contact pen scale for general user controlled proximity detection. Now this is used to calculate an auto contact length (factor applied to element length) for the purpose of proximity detection (required for thin plates). Instead, extend the use of this calculation to general proximity detection between two faces. A couple considerations:

• If it is actually auto contact, then this factor can be whatever the user wants.
• If not auto contact, don't allow the proximity length scale to be less than the (default) length that is used now.