iLogic Formula with boolean in the math operation not giving expected results

[dwerner]

I am trying to capture the the total area of sign boards mounted to a structure.  The structure can have 1, 2 or 3 sign mounted to it.  Below is my ilogic formula based on user parameters.  I captured the current values above and below the formula

D1 = 2440 mm
B1 = 5 m
D2 = 3050 mm
B2 = 5 m
D3 = 610 mm
B3 = 7 m
Sign_Count = 2 ul

Sign_Area = D1 * B1 + (D2 * B2 * (Sign_Count >= 2)) + (D3 * B3 * (Sign_Count >= 3))

Sign_Area = -3.05 m^2

 I was expecting the area to be 27.45.  When I use the same structure formula in Excel is gives the answer of 27.45.

I was trying to avoid 

If Sign_Count = 1 then
     Sign_Area = D1*B1
ElseIF Sign_Count = 2 then 
     Sign_Area = D1*B1+D2*B2
ElseIF Sign_Count = 3 then
     Sign_Area = D1*B1+D2*B2+D3*B3
endif

[ryan.rittenhouse]

Not sure why it's evaluating like that - I don't have an answer for the logic end. This may not be of use to you, but if you have the signs modeled and want to pull the area of them straight out of the model, you can:

Sub Main()
	
	Dim signFace As Face
	Dim signArea As Double
	
	'Use this is you have named components and faces
	Dim signComp As ComponentOccurrence = Component.InventorComponent("Sign1")
	signFace = GetFace(signComp.ComponentDefinition, "Front")
	
	'Use this is you want to pick the sign and face
	signFace = ThisApplication.CommandManager.Pick(SelectionFilterEnum.kPartFaceFilter, "Click the front of the sign").NativeEntity
	
	signArea = signFace.Evaluator.Area / 10000
	
End Sub 'Main

Function GetFace(def As PartComponentDefinition, faceName As String) As Face

    For Each bod As SurfaceBody In def.SurfaceBodies
        For Each f As Face In bod.Faces
            Dim attSets = f.AttributeSets
            If attSets.NameIsUsed("iLogicEntityNameSet") Then
                Dim attSet As AttributeSet = attSets.Item("iLogicEntityNameSet")
                For Each at As Attribute In attSet
                    If at.Name = "iLogicEntityName" Then
                        If at.Value = faceName Then
                            Return f
                        End If
                    End If
                Next
            End If
        Next
    Next bod
    
    Return Nothing
    
End Function

[dwerner]

Interesting.  nice to see an demonstration of interacting with the model with picks.   Oddly enough, the signs themselves and the support structure for the signs are two different contracts.  The signs themselves actually never show up in the design drawing other in a table to give their position for mounting, and over all dimension for determining the structural requirements of the sign support components.  My basic check is to ensure the total sign board size is either under 45 m^2 of perform a special location calculation to determine a new sign limit.  So for the time being no signs in the assembly I am working on.  Though nothing to say I won't add it later as a follow up.

[Curtis_Waguespack · Accepted solution]

@dwerner, I think this would work for you. 
Hope that helps, Curtis

Sign_Count = 2
For i = 1 To Sign_Count
	Sign_Area = Sign_Area + Parameter("D" & i) * Parameter("B" & i)
Next
Sign_Area = Sign_Area + 3.05 m^2

MsgBox(Sign_Area)

Sign_Count = 2
For i = 1 To Sign_Count
	Sign_Area = Sign_Area + Parameter("D" & i) * Parameter("B" & i)
Next

MsgBox(Sign_Area)

[Curtis_Waguespack]

After setting this part up I noticed this actually did return 27.45 for me though

Sign_Count = 2
Sign_Area = D1 * B1 + (D2 * B2 * (Sign_Count >= 2)) + (D3 * B3 * (Sign_Count >= 3))
MsgBox(Sign_Area)

[dwerner]

I think you meant i instead of 1 within the for loop.  minor typo.

What perplexes me is why the +3.05 m^2 requirement  seems strange.

[dwerner]

Thank you for confirming that there is something amuck with my model since my formula is working for you!  Apparently Inventor just hates me 8)

[Curtis_Waguespack]

---

@dwerner wrote:

I think you meant i instead of 1 within the for loop.  minor typo.

What perplexes me is why the +3.05 m^2 requirement  seems strange.

---

Doh! 

You're exactly right. That explains the +3.05 m^2 part also, which seemed odd to me too... not sure what it was doing, but this works

[Curtis_Waguespack]

---

@dwerner wrote:

Thank you for confirming that there is something amuck with my model since my formula is working for you!  Apparently Inventor just hates me 8)

---

it could be the Length units for your document? Maybe

Tools tab > Options panel > Document Settings > units tab

[dwerner]

Is there something off in my model?

[dwerner · Accepted solution]

so I did a wee bit of msgbox debugging since i could not step through or watch the evaluation.  On my system I found a strange result.

Sign_Count = 2
msgbox(Sign_Count >=2)
'result "TRUE"
msgbox(1*(Sign_Count >=2))
'result "-1"

I would have thought the results of TRUE x 1 would have been 1, not -1.  When I adjust the formula with - put before the bracket for the boolean check, it works for me.  Wonder what setting causes TRUE to convert to -1?

Further research into the matter shows that VB.net uses -1 for TRUE and 0 for FALSE.  Further reading also highly suggests not to rely on the numeric value for True or False in a formula but instead to deal with the True or False cases in other ways.