2.2 - Advanced Modeling Tools: Shell and Cover

Shell creates a hollowed-out form with a given thickness from a solid, and Cover creates a face from a closed loop of (not necessarily coplanar) edges. These are simple but powerful tools for quickly creating forms from just about any geometric shape.

In this exercise, we will create a penthouse on top of the Encode Campus Sample Model.axm using shell and cover, while touching on various other modeling tools that were not covered by the FormIt Primer Part I. If you have not already, you can download the file above from the FormIt Primer Part 2 Dataset..

Modeling the Penthouse Mass

First we will create the mass form for the penthouse, using a variety of modeling tools. Feel free to either follow along verbatim or get creative and make your own design!q

1 - With the Encode Campus Sample Model.axm open, go to the Penthouse scene (or adjust your view and layers so you can see the roof of the main building).

2 - Let’s use some geometric primitives to quickly create a form:

  1. From the Standard Toolbar, select Cube (Alt + B) from the Create Primitives dropdown button.

  2. With the cube’s preview active, press the Tab key to set its dimensions (Width: 100’, Depth: 15’, Height: 10’), and then place it on the roof in a similar location to the image below. Similar to placing a component, you can rotate the cube by 90-degree intervals by pressing Space.

  3. Add a second Cube (Alt + B), (Width: 30’, Depth: 15’, Height: 12’), and rotate it 8.5 degrees, so that it matches the angle of the façade and makes a 98.5 degree angle with the long cube. Position this cube so that it intersects the long cube similar to the image below.

Note: Make sure both cubes are sitting directly on the roof surface. It is easy to accidentally change their elevation when moving them around.

3 - To make the box into what will eventually be a more dramatic space, we will angle some of its faces using the Tilt Face (TF) tool.

  1. Select either the NE or NW face of the angled box, right-click to bring up the Context Menu, and select Tilt Face (TF).

  2. Tilt the face by an angle of 15 degrees outward. Just like many FormIt tools, you can either press Tab or just start typing a number.

  3. Do the same for the adjacent face as shown.

Note: While in the Tilt Face (TL) tool, you can rotate the selected face about any axis you would like. Just use the circular grips to adjust the axis of rotation (dotted blue line).

4 - To make the form a bit more complex, let’s add some curves:

  1. Open the Create Primitives dropdown, but this time select Cylinder.

  2. Using the default radius of 6’ and height of 12’, place the cylinder anywhere on the roof for now.

  3. Using the Non-Uniform Scale tool, stretch the cylinder in the direction parallel to the long box by 300%. To learn more about the scale tools, refer to chapter 1.11 – Import Models with Content Library.

  4. Move the cylinder so the center of its long axis is along the edge of the long box, as shown. Don’t forget that constantly toggling between views, like the Top View (VT) used in the second image below, can be helpful for modeling and moving objects into place.

Placing and scaling the cylinder
Moving the stretched cylinder into place

Note: Even though the shapes we have placed thus far overlap, you can still individually select each one by double-clicking on any of its faces or edges. This is because any time you place (or create) a closed shape, FormIt recognizes it as a ‘body’ and will keep track of its geometry together until you intentionally join it with something else.

Joining and Cutting

We can use the Join Geometry (JG) and Cut Geometry (CG) tools to merge the shapes we have just created into a single form.

1 - First, we will do the joining:

  1. In the Standard Toolbar, click on the Advanced Geometry Tools dropdown and select the Join Geometry (JG) tool.

  2. This will bring up the Join Geometry Wizard. Similar to using the Sweep tool back in chapter 1.9 – Adding Details, all advanced geometry tools have their own wizard to guide you through their use.

  3. Select one of the boxes. Make sure to double-click to select the entire solid, not just a single face. Notice that the wizard will automatically move on to the next step.

  4. Select the remaining box.

  5. Click on the checkmark in the wizard to complete the join. To check if it worked, you should be able to select all of your newly joined geometry with one double-click.

Note: If your current selection already contains geometry that can be joined, like two (2) or more overlapping solids, you can also access the Join Geometry (JG) tool from the context menu by right-clicking on your selected geometry.

2 – Now, we will cut the ellipse out of our boxy mass:

  1. With no geometry selected, go to the Advanced Geometry Tools and click on Cut Geometry (CG).

  2. The Cut Geometry Wizard will appear. Make sure to read what it says carefully, because when cutting, unlike joining, the order that you select the geometry is important.

  3. First Select the solid to be cut into, which in our case is the boxy mass we created above.

  4. Next Select solids to be removed, which is the elliptical cylinder.

  5. Click on the checkmark in the wizard to complete the cut.

Note: Notice that the ellipse set to be “removed” will not be deleted, but its geometry was carved out of the box geometry, as we will see in the next step.

3 – To finish up, drag the top face of the ellipse down by 11’-6”, so it becomes a 6” thick platform. We can use this as a start to our roof garden patio later. You should now be able to clearly see the cut we just made.

Shell and Cover

Now that our mass is constructed, we can use Shell Solid(s) (SH) to quickly create a space with walls, a floor, and roof that all have thickness. Then we can use Cover (CV) to quickly create some glass faces for our penthouse.

1 – If you select an entire solid, the shell tool will create an offset ‘shell’ from the selected geometry on all sides - making it hollow but still covered on all sides. Often, the more useful way to use the shell tool is by selecting the faces of a solid that you do not want to include in the shell. Sounds confusing? It is actually quite simple, let’s give it a try below:

  1. From the Advanced Modeling Tools, select Shell Solids(s) (SH).

  2. In the Offset Distance dialog that appears, enter a thickness of -8”, and press OK.

  3. Using single-clicks, select just the three faces we want to remain open; the curved surface and the two tilted faces we made previously.

  4. Click on the checkmark in the wizard to complete the shell.

Note: A negative shell offset value will offset the new surfaces towards the inside of the shape, while a positive value will offset them towards the outside.

Shell in progress
Finished Shell

2 - Now we almost have a complete penthouse, it is just missing a few walls. We can use the Cover (CV) command to quickly create some surfaces from a selected loop of edges. First, let’s cover the curved area:

  1. From the Advanced Modeling Tools, select Cover (CV).

  2. Select all four (4) edges around the curved opening. You may need to use the Tab key to select an entire curved edge at once.

  3. Click on the checkmark in the wizard to complete the cover.

Note: Whenever you are prompted to make a selection while using a wizard, be it one of the advanced modeling tools or a dynamo script, you do not need to hold Ctrl or Shift to deselect or select multiple objects. To remove a previously select object, simply click on it again.

3 - Do the same thing for the openings where the tilted faces were. If you have been following along with our design, there will be eight (8) edges you need to select.

Finishing Up

To finish up the penthouse, we will sample a few ways to make quick curtain walls out of the surfaces we just created.

1 - Let’s start by using the built-in Dynamo Storefront Curtainwall script. If you are new to using Dynamo in FormIt, check out chapter 1.10 - Computational Groups with Dynamo in the FormIt Primer Part I.

  1. In the Dynamo Palette, make sure the folder dropdown is set to Dynamo Samples.

  2. Scroll down and click on the Storefront Curtainwall tile, which will launch the wizard for this script.

  3. In the canvas, select the two angled surfaces we just made with the Cover (CV) tool.

  4. Click on the checkmark in the wizard, and then wait for the script to run. It may take a few seconds.

  5. (optional) Update the script parameters and re-run it until the mullion layout it adjusted to your liking. The inputs we changed from their default values were:

    1. Mullion Depth: 0.5

    2. First Horizontal Mullion Spacing (on center): 4.833

    3. Typ. Horizontal Mullion Spacing (on center): 4.833

  6. Paint the surfaces we used for the script’s input with the transparent material of your choosing. We used Glass - New.

Note: If you want to learn more about advanced uses of Dynamo within FormIt, check out the Primer Part II chapter that deal specifically with Dynamo: Dynamo FormIt Nodes.

2 – Unfortunately, the script we used in the last step does not always work well on curved surfaces. Another trick to quickly give a surface a curtain-wall appearance to a somple surface is to use a material with a Cutout map, which makes part of the material transparent. FormIt comes with three (3) built-in materials like this for curtain walls. All we have to do now is grab one, paint our surface, and then scale it using the Adjust Material Placement tool:

  1. In the Materials Palette, import the Glass – Storefront with Spandrel from Material Samples > Glass+Glazing, and then paint the curved surface with this material. For more information on importing and using materials, see Chapter 1.7 - Paint with Materials in the FormIt Primer Part I.

  2. Right-click on the curved surface you just painted and select Adjust Material Placement (MP).

  3. Using the up and down arrow, scale the material vertically until the mullion above the thin horizontal window band is just visible below the top edge of the curved opening. With our design, we have found that entering a height of 8’-7” works well.

  4. Now using the horizontal arrow, scale the material horizontally so that the vertical mullions are about 3’ apart, similar to the spacing used in our tilted curtain walls. With our design, we found that a value of 9’ works well.

Painting with a cutout curtain wall material
Stretching the material vertically
Stretching the material horizontally

3 - Add some finishing touches to the design! In the finished image below, some of the things we did to enhanced our roof include:

  • Used Sweep (SP) to add a parapet, bound to the roof’s outline.

  • Used the out-of-the-box Dynamo script Array Along Path to place roof pavers around the roof perimeter.

  • Added various tile materials to the penthouse, using the Adjust Material Placement (MP) tool from above to rotate and alight their joints.

  • Downloaded, converted a .skp file of a solar panel, and then imported it into the model. To learn more about importing various file types, refer to the Advanced Export and Import section.

  • Added some string lights using the Generate String Lights plugin – To learn more about plugins, make sure to check out the next chapter in Part II: Plugins.

Feel free to put your own creative touches to the model, and explore some of the other advanced modeling tools we did not get to in this chapter! You can compare your creation to our finished sample model by downloading and opening the Encode Campus Sample File_Completed.axm from the Encode Model Data Set.

Scene in completed model.