Intersecting roofs & dormers

[Eric9]

I think I posted this to the wrong section earlier ... oops. So I'll try one more time.

I am a new user and self trained so forgive me if these questions seem a bit out of touch...

What is the best way to intersect roofs? I have come across this dilemma a couple times in my model. One, when adding a shed dormer adjacent to a gable dormer and two, when modeling the main roof, which is two perpendicular intersecting gable roofs.

I'll try to explain the geometry of the second item above: The house perimeter shape is a rectangle. The gable ridge boards form a "T" when viewed from above. I have tried creating two separate rectangular polys as the foundation for the roof, which works, but the two roof shapes pass through each other. I also tried modeling a single block "T" shaped poly from which I created a roof. Then I modified "T" back into a rectangle that matched the walls. I can get the the top part of the "T" (the length of one of the gables) to be only a fraction of an inch longer than the width of the body of the "T" (the width of the other gable). However, when the roof perimeter truly matches the rectangular shape of the outside walls, Vectorworks gives me an error message that say something like "the roof was too complicated."

What is the best strategy for making a dormer without a window? Is there a symbol without any geometry that can be used for this?

[Jonathan Pickup]

try making a dormer with a window symbol, but make the symbol nothing more than a 3D locus point.

Also, as your roofs get more complex you might want to look at my Architect Tutorial manual...

[seanSF&A]

I am also self trained with the aid of the packaged manuals and also the VW training CD's.

None of the material supplied by NNA seems to show how to intersect roofs, creating new valleys.

Whilst I respect the fact that Jonathan would like to protect his intelectual property in the form of his training manuals, the fact is that this problem needs an answer from NNA. It is not acceptable that a single issue like this can only be answered by purchasing a complete new manual.

sean

[mike m oz]

OPTION A

The roof tool works as long as you do not try and have vertice points that are colinear - each vertice must represent a change in direction.

So if you make your change of direction very minor (for example the width of your eaves gutter) the roof will model correctly and you can then turn each hipped end into a gable by clicking on their handles one by one and selecting the gable option with your required overhang.

OPTION B

Create your two intersecting roofs separately and turn the ends that you require into gables.

Where they intersect there will be areas of roof that you do not want. For the first roof draw two triangular polygons to represent the areas of roof that you wish to remove. Select both of these and Cut them from the drawing. Select the roof and then Select Edit Group from the Organise Menu - this will takle you into the roof group. Do Paste in Place and then Exit the Group - you will find that the required areas of roof have been removed. (Note - do not double click on the roof as this will take you to the Edit Roof Settings dialog box.)

Repeat the above process for the second roof and you will have the result you want.

COMMENTS ON OPTION B

- You can reverse the 'removal' by editing the group and deleting the polygon or polygons.

- If you end up with a line of roof along the eaves just make your cutting triangles slightly bigger than they need to be so that they go outside the eaves line.

MORE COMPLEX ROOFS

Option B can be used to refine a simple roof into something much more complex.

For example a mansard roof can be modelled from two separate roof objects:

- Draw a polygon representing the outline of your roof.

- Offset it inwards by the required distance and then Copy it.

- Use the first polygon to create a roof with a pitch of say 70?.

- Edit the Group (from the Organise Menu) and Paste in Place. This will cut the top of this roof off at the required distance in.

- Use the second polygon to create another roof with a pitch of say 1.5?.

- Move the second roof to the appropriate height and you will have a mansard roof. (You may have to play around with the roof thicknesses to get exactly what you want but this is not hard.

There are other possibilities as well - you just need to learn to think laterally and not just assume that something can't be done.

There will be times however where you have to model each roof face separately. You can expedite the process by using the Roof Tool to get close, and then by ungrouping it you will have individual roof faces which you can modify as you need.

[ 03-20-2005, 06:27 AM: Message edited by: mike m oz ]

[islandmon]

There will never be a single 'magic' solution for every case. I've found that using the basic roof shape to set-up the frame and then doing all the real work with the Roof Framing is more intuitive ( creating symbol groups along the way). Everything I do is from the structural-material- contractors point-of-view. Hence, the power of the Roof Framing : ) Roof surfaces are ultimately a function of the underlying structural frame.

[seanSF&A]

Mike,

Thanks for your reply. However I have tried and retried this method and keep getting the same results as follows.

I draw two rectangles at rightanges to each other then overlap them to create the basis for the intersecting roofs. I then draw a polygon over the part of the secondary roof that is to remain, cut, select the primary roof, edit group, paste in place, exit group. That works, i get a neat cut-out in the primary roof where the secondary roof intersects.

I then draw a polygon over the remaining part of the secondary roof, cut, select secondary roof, edit group, paste in place, exit group.

That doesnt work. Each time i try it only removes one roof slope of the two sections (gabled roof or one of three if left as hipped). Each time i re-enter the secondary roof group, the part of the roof that remains, has somehow come to the front, over the polygon, whilst the the section that was removed has remained behind the polygon. By sending the roof slopes behind the polygons, they are once again covered by the polys, then on exiting the group it reverts again. Every time it keeps sending all but one roof face back up to the front, covering the polygons. Most frustrating. What am i doing wrong?

[seanSF&A]

PS.

I found the mansard roof worked great as well, thanks.

sean

[Robert Anderson]

Sean, it's hard to tell from your description, but why not just join the two rectangles using the "add surface" command before you create the roof, then edit the roof on a face-by-face basis to add gables? This would be a more 'normal' workflow for VW roofs.

[mike m oz]

Sean - I tried and experienced the same problem you have described.

I suspect that the Roof Object routine doesn't like the cutting triangle edge vertex coinciding with the roof eaves to gable vertex.

I overcame the issue by moving each of the triangles towards the eaves by 10 mm (3/8"). The cutouts in each roof then worked okay. This also removed the roof eaves line which also contiued to run across where the cutout was supposed to occur.

[mike m oz]

Sean - I also tried doing it as Robert suggested, but overlapping the two rectangles by 10 mm (3/8") so that you can still get the gable form at the top of the 'T''. It worked fine and is quicker and easier than the method I suggested.

It is a bit of a fudge (by 10 mm) but then so is the method I suggested. In both cases the 10 mm is visually insignificant so to my mind it is acceptable to get the result you require.