Saturday, June 12, 2010

Roof Object - I was WRONG again !!! Part 11

I can't believe it !!  I am flabbergasted.  This beauty of a tool was hiding yet another secret.  One that I said it couldn't do.  I don't think Autodesk knew.  EVEN the roof creator himself didn't know!!  But I am about to show you what we all missed - IT CAN BE DONE!


This roof object (RO), that was created back for ADT1 can overlap itself.  Yes it's true it hasn't changed in all that time and it CAN do what we all thought it couldn't.  You just gotta know how to caress and seduce it.  Actually it's even Much easier than that.

Take a look at these examples and see.  This picture is of just ONE RO.
I discovered this all by accident and there must have been someone else out there that also discovered this but perhaps because you have been told to explode to roof slabs you didn't bother to explore.  But my obsession with this clever tool continues to lead me to discover new tricks.

So how's it done.  Simply by creating extra edges & a gap which allows the object some space and you the opportunity to add an overhang or underlap. These gaps can be made smaller than you can see on a print.  

This example is the centre hip in the roof above. It both overhangs and underlaps itself.  I've shown the gap big enough to see but it can be very small and I turn this blue (eave) line off in display anyway.  The red lines would need stretching into position once you create the roof object but you would then have the RO valleys showing to know where to stretch it to. (It should become obvious if you do one).
Here are 7 edges from the LHS of the roof as numbered above.  I've pasted in each face slope so you can see it collectively.  You can see the whole hip has a higher pitching height (3200) to raise it above the surrounding roof.  You can see an extra 90d slope added to get the gamblet on edge 6.   The height for those egdes with 90 slopes doesn't matter much.  Here's the strange one.  The overhang to edge 1 controls the length of the underhang!  Sweet!

There's a number of different ways to create this shape but possibly one easy way is to draw a RECTangle over the walls that will hold the raised roof.  Offset a small distance (10?) and then again.  Stretch the top of the outside square down 3 x 10 to get the short 45d edge to line with the valley.  (ok I've not shown square distances above-sorry) You would need to lock your walls so they are not stretched and pref have everything else turned off.  This should give you enough points to snap to as you draw around. Erase the rectangles and STRETCH the top of the shape to meet the created valleys.

You will notice the created eave line snapback controlls the under/overlap width.  Drag it back & forward to see how it controls the extent. 

One more BIG tip when manipulating the Roof Object.  We are taught to pick vertices and drag along.  Good advice for everything else but for the RO, the STRETCH (S) command will give you more consistent results.  If an edge won't move, Stretch it instead.  This tip was fed to me by my young drafter who remarked "I can get the roof object to pretty much do what I like now!".

Ok to restress the rules;
- The Eave line cannot overlap itself but the overhang can but only with a gap between.
- I turn off the eave line as it doesn't represent anything I want to show on my drawings.  There may be times when the eave line path required to get the roof object as you want it is not what you want to show either.
- Stretch - don't drag vertice
-Odin Cary found that you may need to have no general overhang set for the roof to work at first so you may need to add overhangs later rather than set them as default.

-Don't forget you can add vertices by my Trim Trick if you need to add extra edges but it may well be quicker to recreate it.

Here is a closeup on how to get that overhang happening in another common situation. Here the secret is a simple gap where it overlaps.  Again the blue line would be turned off and you are left with a clean roof shape. I would stretch the inside snapback blue line to the left once created to line up with the forward ridge.  This will align the underhang with the main roof as you will see if you do it.

Once you get the hang of the rules these are dead easy to create.  How did we all miss it?

Oh dear...... I am going to have to go back and edit my earlier blogs !! agian!

BTW in case you didn't realise, in IE you can RC on an image and ask to open in another TAB and it will open a larger image you can more easily read.  You can also hold the CONTROL key and scroll your mouse to enlarge a web page display.Cheers
Roof On

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