How to Attack a Ceiling and Rafter Layout LISP

[treaves04]

I am working on putting together a lisp for drawing ceiling joist and roof rafter layouts. I have attached a dwg with a dynamic block that I have made that accomplishes part of my goal. I am just not sure what is going to be the best route to take.

 

I would like to prompt a user to trace the outside of the span area (which would create a closed polyline to trim to). Then specify the direction of the span by clicking and edge (nearest or mid) then clicking a point in the span direction. Next it would prompt for the pitch (0 if none). Where it would convert the pitch to degrees Next it will prompt the user for the inches on center. Where it will then draw a line across the longest section and offset each direction half of the width of the traced area. Next it would trim everything that extended outside of the traced area. Then if a pitch was specified above 0 use the angle in this formula [base length/cos(angle)] (I think) to figure the actual length. A tag would then be assigned to each line labeling it (ex. R11). Then the tag number and the length of the corresponding line will be added to a table.

 

I hope that is clear. I am trying to make sure I have all my ducks in a row and have some good direction. Looking for any and all suggestions. Thanks.

DYN JOIST.dwg

[BIGAL]

Have a look at the Chevron.lsp that I posted here some time ago its a solution to the pline trimming Lee-mac also did a similar function that may be more suited, if you keep a list of the length of the "Entlast" this will give the length of the rafters even for angled walls.

 

http://www.cadtutor.net/forum/showthread.php?82365-Filling-up-one-area-with-a-quot-oriented-quot-polyline.

[treaves04]

Those will surly aid in what I am trying to accomplish.

[spiker7221]

Good morning Treaves04,

I've just finished the same routine for my company. With all the same ideas as yours. But I used the hatch command instead of Offset. I created a hatch pattern for each member spacing...I.E. 12, 19.2, 24. Then I explode the hatch, and label the lines with text. I have a multiplier for each pitch to get the slope length before tagging it. Then simply erase the polyline when I'm done.

 

Not sure if my approach will work for you. Just an idea.

 

Good luck.

Mike

[treaves04]

Yeah that would work. That is how I am doing our roof decking layout. There is just not any labeling with it