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In this video series we will create a detailed model of a pitched roof structure, making extensive use of the Propagate tool and other direct modelling tools.
We start off with the rough shape of our building; materials have already been applied to the different building elements. We’ll turn on ‘Display Composition’ to be able to ‘push-pull’ the different composition plies.
Using ‘Connect with nearest’ we can easily connect these plies to each other.
We will create a detail locally, and then later Propagate this detail over the entire perimeter of our roof. This detail includes a gutter, some coverings, a concrete ring beam and a wooden beam.
We will use ‘Propagate Planar’ to copy this detail. However, to make sure Propagate knows which detail to copy exactly, we will need to activate a section that cuts through all involved detail objects. For this reason, we will move this section plane slightly further into the model, to make sure it includes everything we need.
We are prompted to the select the base solids. These are the solids that define the situation where this particular detail should be applied. In this case it’s the floor slab, the roof slab and the wall. After pressing ‘Enter’ we are prompted to the select the detail objects. These are the objects that we wish to propagate or copy throughout the model, in this case the wooden beam, the concrete ring beam, the two covering elements and the gutter.
After pressing Enter, a 2D detail is constructed. It is an extrusion of this detail that will be applied over the perimeter of the roof. Let’s press Enter.
‘Propagate’ has now scanned the entire drawing for locations where this detail can be applied. A green check mark means that this detail will be applied when pressing Enter. The blue question mark means that the detail will not be applied, in this case because the original detail was only modelled locally; we will click it so it is replaced by an adapted extrusion, to make sure the detail is applied over the entire length of the wall.
After pressing Enter, this detail is applied over the entire perimeter of our roof.
Let’s create a new section to design the connection of the roof with the end walls; we want the facing brick to protrude further into the roof structure.
We will use ‘Propagate Planar’ to copy this detail to the other connections. The base solids are the roof slab and the wall. There are no detail objects in this case. We’ll press Enter to accept the constructed 2D detail, and press Enter again to accept the three suggestions.
We see now that the four corners of the roof are not what they are supposed to be; We can solve this detail once, and again use ‘Propagate’ to copy it to the other corners as well.
We’ll temporarily hide the gutter and these covering elements. We’ll make smart use of ‘push-pull’ and other direct modelling tools to design this corner correctly.
We’ve made sure that the insulation layers of both walls and the roof are now connected properly. We’ll finish this corner by creating ends for the gutter and the covering elements.
Now that we designed this corner correctly, we want to copy this situation to the other three corners. We will use the ‘Propagate’ command for this again.
The base solids are the two walls, the roof slab, the gutter and the covering elements. These solids define the locations where this detail can be applied.
The detail solids are the end caps of the gutter and the covering elements. These objects will be copied to the other locations.
We will propagate this detail as a copy by entering ‘C’ in the command line or by clicking ‘As Copy’ in the context menu.
The three other corners are suggested to copy this detail to. We’ll accept by pressing Enter.
Let’s create a new layer and move the four roof slabs to this layer, so we can easily toggle their visibility. Note that we can change their layer using the rollover tips.
We’ll create the rafters by extruding this boundary and slicing the resulting solid.
For this next step, we will temporarily turn off the subtract behaviour of ‘push-pull’ by going to the settings and typing in ‘pushpull’. If we now push-pull this rafter so that it goes through the insulation layer of the wall, we see that this volume is not subtracted from the wall. This is an interference that we will solve later.
Now that we’ve specified where the rafter ends, we want to copy this to the other side as well. We’ll do this with ‘Propagate Linear’.
The base solids are the wall and the rafter. We want to specify where the rafter ends, so we will use its end face as detail object. By pressing Enter we see that the rafter on the other side of the roof now also has the correct geometry.
We will copy these two rafters to the other end of the roof, again by using ‘Propagate Linear’. You could view these two rafters as elements connecting the two concrete ring beams. Thus, our base solids are the ring beams, and our detail objects are the two rafters themselves.
We’ll choose to copy this detail as a copy, and accept the highlighted suggestion. Note that a small exclamation mark appears to indicate that an interference will be introduced when applying this suggestion.
Next, we’ll copy these rafters and repeat this copy, so that the entire length of the building is covered.
Finally we will slice the rafters to make an L-shaped roof.
Let’s create some more wooden trusses. We’ll use the ‘Linear Solid’ tool and select the profile in the model by clicking one of the rafters.
Using the Manipulator we can easily shift this member so that it connects properly to the rafter and the beam. Remember: you can call the Manipulator by holding down the left-mouse button slightly longer when selecting an entity.
We want this collar tie to be cut off diagonally, like we did on the other side. Instead of using ‘slice’ we can again use ‘Propagate Linear’. The base solids are the collar tie and the rafter; there are no detail objects in this case.
We will also use ‘Propagate Linear’ to copy these wooden members to the rest of our building. You could view these members as a connection between the beam resting on the ceiling slab, and the rafter. Thus, our base solids are this beam and the rafter, whereas the detail objects are the members we just modelled.
‘Propagate’ provides a suggestion for every location where a rafter meets this horizontal beam. Notice again the exclamation marks, indicating the interferences between the objects that will be copied, and the already existing entities. We’ll press Enter to accept this.
The same technique can be used to copy this member connecting the two rafters.
We will now create a ridge beam and again propagate this beam so it is placed between every two pairs of rafters.
Finally we will clean up the interferences. We want our rafters and wooden members to go through the insulation layer of the wall, so we will subtract these volumes from the wall.
Now we’ll use ‘Propagate’ again to copy the connection of these elements. Our base solids are the wall, the rafter and the wooden beam. There are no detail objects in this case.
Note that we still have to manually solve the interferences in this corner; this is because for these two rafters there are no horizontal wooden beams involved; thus, ‘Propagate’ did not identify this situation as a possible location to apply this detail.
In this final video we will model some support elements for the gutter, and finalize the roof design.
Once we’ve created one of these supports, we can use ‘Propagate’ again to copy it throughout the rest of our drawing.
We will subtract the volumes of the rafters and collar ties from the roof solid, so they are no longer interfering.
By isolating the roof slabs we can see that there are now recesses in the roof slabs for the rafters and collar ties.
Finally we’ll pull this slab through the structural masonry layer of the wall and use ‘Propagate Planar’ one last time.
