Dynamic block: scaling a circle around a center point using diameter

[mrichardsKN4R4]

Goal 1: Dynamic block for a tree trunk (existing trees to remain) that can be scaled around its center point by entering its diameter in the properties panel.

Problem: Linear parameter + scale action only lets me scale by radius, or scales diameter from one edge of the circle, not from the center.

Goal 2: Tie an attribute to the parameter so that you can enter the DBH on block insertion, instead of opening properties.  I'm not actually sure if this is possible, but I remember having a block with similar functionality in a previous office.

[j.palmeL29YX]

goal 1: 

see attached suggestion

goal 2: "... enter the DBH on block insertion"   ???

[mrichardsKN4R4]

Thanks for #1 - that works.

#2 - sorry,  Tree lingo.  DBH = diameter at breast height.   I want to be able to set the diameter of the symbol when I insert it.  The block also has a "tree tag" attribute definition, so I don't want to just scale the entire block.

[j.palmeL29YX]

BTW: If you want to set the diameter during the insert, you don't need any dynamic block. Create a "normal" block with diameter=1 and set the scalefactor to the whished diamter while you insert the block. Or what I'm missing?

[j.palmeL29YX]

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@mrichardsKN4R4 wrote:

The block also has a "tree tag" attribute definition, so I don't want to just scale the entire block.

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Oops, I read this after posting my previous answer. 

If you need an attribute which "reflects" the current diameter, you can scale the block while inserting and use an attribute whose default value is a field which reads as blockplaceholder the current scale factor. Doesn't that meet your goal?

[mrichardsKN4R4]

Not quite, because scaling the block on insertion will still scale my other attribute text - unless I'm missing something?

[j.palmeL29YX]

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@mrichardsKN4R4 wrote:

Not quite, because ...

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Ok, that happens if we know only the half of the truth  😉 

At the moment I don't know further help.