topic Re: Angled Roof - How do I construct a skillion roof w/ 2 an in Modeling

Angled Roof - How do I construct a skillion roof w/ 2 angles

Anonymous — Tue, 23 May 2023 13:10:52 GMT

With the roof tool how do I construct a skillion roof with two angles/pitches.

For example.
Select the roof tool,
Selected the simple skillion roof,
enter the first node of the roof pivot line,
then the second node (usually vertical or horizontal)
draw a simple square roof with a 6 degree pitch.

Now this is where it gets tricky.
If I move the roof pivot line to an angle I get a roof with two angles.

What I would like to know is how to work out where or what angle to place the roof pivot line to get a main roof pitch at 6 degrees and be at 10 degrees (in its side elevation)

Is there any geometry or simple way of working this out.

Thanks in advance.

Brendon

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Thomas Holm — Tue, 20 May 2008 08:37:54 GMT

I'm not sure exactly what you mean. The pivot line is by definition horizontal, and the slope angle is defined perpendicular to the pivot line. Neither of the "two angles" you mention is the true slope angle.

But to approach this in a less theoretical way, I'd simply construct this by making one test roof 6° like you said, another with slope angle 10° and pivot line perpendicular to the section cut direction and then intersect them. Then make a section in the intersection, measure the angle and make your final roof with that slope, perpendicular to that section.

I'm sure there are other and maybe better ways.

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Barry Kelly — Tue, 20 May 2008 09:19:18 GMT

There was a soulution to this (or something very similar) in this forum some time ago.
The problem is coming up with the appropriate key words to do a search that will get a result - not jus a thousand posts about roof pitches.

Thomas' method should work but another would be to work it out mathematically or graphically.
At a certain length along the 6° pitch (say one metre) determine the height or rise of the roof.
How far along the 10° pitch would you have to go to get to the same height.
The pitching line will then run parallel to these two points.

I'm sure there is an easier way like stretching in 3D or finding that other post.

Barry.

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Tue, 20 May 2008 09:48:55 GMT

I would start with two (temporary) connecting roofs with the correct slope angle. Then stretching graphically (=trial and error) in the 3D window to achieve the best possible result. I still have not found another way of doing this...

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Thomas Holm — Tue, 20 May 2008 12:10:11 GMT

Joeri wrote:
I would start with two (temporary) connecting roofs with the correct slope angle. Then stretching graphically (=trial and error) in the 3D window to achieve the best possible result. I still have not found another way of doing this...

I think my way is faster

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Tue, 20 May 2008 14:30:50 GMT

The method Barry may be referring to is one Link explained
in a thread that I can't find but I copied his post and diagram.
See attached
Peter Devlin

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Tue, 20 May 2008 16:34:59 GMT

Use Meshtool

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Djordje — Tue, 20 May 2008 17:22:37 GMT

If you know three points of that roof, and you do, define them in 3D (place anything that you can snap to in 3D window), open 3D window, do the roof plane throught those three points, shape to taste.

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Barry Kelly — Wed, 21 May 2008 02:14:59 GMT

Djordje wrote:
If you know three points of that roof, and you do, define them in 3D (place anything that you can snap to in 3D window), open 3D window, do the roof plane throught those three points, shape to taste.

There - I knew there was an easy way - thanks Djordje.
I've never had the need to define a roof in 3D though but it works really well.
As Djordje says the trick is to define the three known heights in 3D so you can snap to them.

Barry.

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Mon, 26 May 2008 05:00:11 GMT

Ok,
following are a couple of snap shots of what I'm after.

The first is showing with two roof in plan what I trying to do with one roof and not using the mesh tool.

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Mon, 26 May 2008 05:03:03 GMT

The second is again a plan view but rotating the roof pivot line.

(This is what I'm chasing, how to work out the rotation angle of the roof pivot line to achive a 15° pitch in one elevation and in the other elevation 30° pitch - see more attached images).

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Mon, 26 May 2008 05:05:30 GMT

Elevation of roof with two pitches. Elevation 1

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Mon, 26 May 2008 05:06:53 GMT

Second elevation perpendicular to the prevoius elevation

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Mon, 26 May 2008 05:07:56 GMT

Final 3D view of want I'm chasing

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Thomas Holm — Mon, 26 May 2008 14:03:26 GMT

I think we understood your goal, brendon. You've got four (I think)different methods proposed. Did you try them?

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Wed, 28 May 2008 00:40:04 GMT

What you are looking for is tricky, and not just because of AC's level line method for defining roofs. It is inherently complicated to define a planar face of more than three points at an arbitrary angle. All the more so if you don't account for the roof thicknesses.

Following is the only way I know to do what you want accurately in ArchiCAD (short of a nasty experience with trigonometry and a calculator).

1. Make two roofs at the desired pitches (as you have already done). Make them zero thickness to eliminate height problems caused by the different pitches.

2. With the shallower roof selected, command/ctrl click to get the elevation of the roof at its high corner as shown (you can also get this from the "Z" coordinate in the 3D window) and copy the value to the clipboard.

3. Select the other roof and then use Design > Create Roof Level Lines. Paste the value copied above to get the line at the desired height.

4. Draw the final roof with the pitch reference line from the corner of the first roof to the intersection of the level line with the opposite wall as shown.

5. Elevate and adjust the pitch of the final roof as needed in 3D.

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Thu, 29 May 2008 04:14:04 GMT

Thanks Mathew,

Thats exactly what I was looking for and it works.

Much easier then the other methods proposed (Thomas).

Thanks.

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Thu, 29 May 2008 05:18:14 GMT

Ok.

It's not exactly correct/perfect, however this method is 98% there.
I would have liked to eliminated step 5 but will do.

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Barry Kelly — Thu, 29 May 2008 07:40:32 GMT

brendon wrote:
Ok.

It's not exactly correct/perfect, however this method is 98% there.
I would have liked to eliminated step 5 but will do.

Draw the two roof planes at your various pitches with zero thickness as Matthew suggested.
Then select and view in 3D.
Now draw the real roof - you will be picking three points to define the roof slope.
The first point is the low corner where the 2 roofs start.
The second point is the high side of the first roof (15°).
The third point is the high side of the second roof (30°).
Now all that is left to do is define the shape of the roof plane - ie two diagonal points for the rectangular roof or more more the irregular polygon method.
Barry.

Re: Angled Roof - How do I construct a skillion roof w/ 2 an

Anonymous — Thu, 29 May 2008 14:43:07 GMT

brendon wrote:
It's not exactly correct/perfect, however this method is 98% there. I would have liked to eliminated step 5 but will do.

To the contrary, it is precisely correct (at least within the limits of the floating point accuracy of the system). "Perfect" is more of a value judgment 😉

It seems step 5 can be skipped, along with steps 2 & 3, by using the method Barry suggests. I guess I'm too stuck in my old ways sometimes. I haven't drawn many roofs in 3D and didn't realize that you can set the pitch by the 3 point method. Thanks for the heads up Barry!