Constraint formula Limits?

[Gatekeeper101]

So I'm creating a block with a block table and constraints. The constraints such as Geometric Constraints work just as assumed. When adding in dimensional constraints we start to have more fun. So I have dimensional constraints that use other dimensional constraints to manipulate itself.

 

EX. dimconC = (dimconB-dimconA)

dimconA is 12

dimconB is 14

dimconC would be 2

Now when ever dimconA or dimconB change dimconC would populate accordingly.

 

With this I wanted to make an attribute that could be placed in instead of a dimensional constant.

 

EX dimconC = ((Att1*dimconB)-dimconA)

Att1 is 02

dimconA is 12

dimconB is 14

dimconC would be 16

 

However when trying to place in formula that references a attribute I keep getting an error "A DEPENDENT EXPRESSION CANNOT BE EVALUATED" So I assumed it was missing an expression from the attribute, however once entering an expression in for it I still get the same error.

(full error message attached)

 

Is this something that is not allowed at all or have I over looked something?

All help would be nice, if I've left a detail out please just ask and I'll fill it in the best I can.

Thanks in advanced!

[SLW210]

Without seeing your attribute and block hard to say the cause of this, but it should be doable.

 

READ THIS

[Gatekeeper101]

Thank you for the quick response. This is a nice work around of what I was attempting to do. (stumbled apon this myself )

 

The example is showing a field to the parameter, the only way to modify the parameter is either by a grip point (if you set it up) or through the properties panel.

 

I was working on this late and after talking with an engineer I work with, the example provided is how it was decided to proceed forward. I guess some times the easiest solution is the best solution.

I'll upload the block once I'm done to show what I was making.

 

I wanted to go just the reverse. I wanted the Attribute to assist in the definition of the distance. So when the block was used and the user was prompted for the "Distance" that attribute would then be read by the constraint parameter. Maybe once the block is a working product I'll attempt again to get a Constraint Parameter to read from an attribute.

 

I should be done with it shortly . . . with any luck.

 

Again thanks for the quick response !!

 

***** Update *****

 

I've loaded the block and a snap shot of the parameter manager (Show the formulas used in the block)

 

I hope this inspires people, rather to push blocks to the limits, or avoid mistakes I've made.

AV300_PROJECTOR-TO-SCREEN+TOLERANCE.dwg

Edited August 26, 2011 by Gatekeeper101
Uploaded Block