Reduce dynamic block length by a set dimension

[DragonDesigns]

I have a simple dynamic block a rectangle to represent a brick with one dynamic dimension for the length.

Is there a way to reduce the length for multiple blocks by say 20mm?

I can use q-properties and take 20mm from the dimension for each block, or use grips.

Thanks.

[hwalker]

You might be able to do it with a lisp, but not with selecting properties if all the dimensions are different

[Libbya]

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@DragonDesigns wrote:

I have a simple dynamic block a rectangle to represent a brick with one dynamic dimension for the length.

Is there a way to reduce the length for multiple blocks by say 20mm?

I can use q-properties and take 20mm from the dimension for each block, or use grips.

Thanks.

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If the length parameter is the same for all of the blocks, then you can simply use q-select to select them and then edit the parameter value in properties.  If they are all different lengths, then it can be done but is more complicated.  Post your block and an example file to play with if you want more input.

[DragonDesigns]

I have attached an extract of an elevation of some brickwork.

We have an angled line of two types of brick. The dynamic block was a fast way of getting the size of the brick slips and any over 215mm. I also added a line to mark the 215mm size.

I often need to reduce or increase similar dynamic blocks, brick or timber slats, by a set dimension.

This was in a bit of a rush, so in retrospect, there must be a better way of doing it.

Thanks All.

[Libbya]

I looked at the file and read your description and I still do not understand what functionality/workflow you are wanting to achieve.  

[DragonDesigns]

I want to be able to reduce/increase all dynamic blocks (of different lengths) by a set figure, say, plus 20mm.

[Libbya · Accepted solution]

Here's your block back.  You can select all of the blocks and go to properties.  Under the 'Custom' section you will find a parameter called "PLUS-MINUS" and its value will be 100.  It's value will ALWAYS be 100 regardless of what you enter in properties.  If you enter 110, then all of the selected blocks will increase in size 10 units regardless of what their size currently is.  If you enter 90, then all of the selected blocks will decrease in size by 10 units.  Hopefully you will get the idea.  

[DragonDesigns]

Thanks, that is perfect; it shows how much I still have to learn after 36 years of using AutoCAD

I have looked at the block if it's not too much trouble, how have you done that?

[Libbya · Accepted solution]

It's strange but it isn't complicated.  The PLUS-MINUS linear parameter is drawn at 100 units.  Its endpoint stretches the other linear parameter and brick edge, but it also does the tricky part of moving the added chained point parameter.  That chained point parameter in turn stretches the basepoint of the PLUS-MINUS parameter.  If the endpoint is moved 10 units, it moves the point/stretch which stretches the parameter basepoint the same 10 units, making it so the PLUS-MINUS always equals 100 units.  It's the proverbial snake eating its own tail.  Because it always equals 100 units, all the blocks show the same value in properties so it can be adjusted there.  Hopefully that makes sense. 

[DragonDesigns]

Thank you for that. I will have a closer look at it later. I am already thinking of many places where I can use it. It is easy to modify a few items, but if I have to change dozens of them, proper planning will save a lot of effort, especially now I know it can be done.