How to Model a Wall Opening with an Arched Top and Slanted Reveals

by GRAPHISOFT and lnagy · updated: 02.09.2012

Sometimes you may wish to create a Wall Opening that is not available as a Door/Window Library Part is ArchiCAD. In this case one of the choices is to model the special Door/Window Opening shape and save it as a Window/Door Library Part. There are articles on ArchiCADWiki outlining this procedure: Custom Shape Door Window and Create Custom Opening.

Let us now consider a more complex example, in which we wish to create a Wall Opening that has an arched top and slanted reveals.
The following article details how to achieve this.

Let us take a look at the following image.

picture1.PNGHere is a Wall into which we want to place this special Wall Opening. The Side View of the Wall Opening is drawn below the Wall.
There are several things we need to solve here:The first is the geometry of the Wall Opening. For this we are going to model the shape of the Opening using the Ruled Geometry Method of the Shell Tool.
Then we will cut the Trimming Body of the Shell out of the Wall’s body. This will give us the result in 3D.

However, as you know, SEO-type operations performed on construction element types is not reflected in the Floor Plan representation of the SEO-ed element (the two exceptions are the upgraded Roof Tool and the newly introduced Shell Tool, both available from ArchiCAD 15).
So we will not see on the 2D of the Wall that it has this Wall Opening in 3D.
In order to solve this will use the trick of modeling this Wall out of 3 Polygonal Wall Pieces. The middle piece will be a trapezoid shape defined by the slanted reveals, and will be able set its Floor Plan Fill so it represents a Wall cut.

Step 1: Create a Wall

Model a single Straight Wall at the desired thickness.


Step 2: Switch to Shell Tool

Switch to the ShellTool and select the Ruled Shell Geometry Method. Activate the Detailed Construction Method and make sure that the Morphing Rule button is set to “Paired”.


Step 3: Draw the first Profile Polygon

Draw the first Profile Polygon of the Ruled Shell by tracing the red polygon drawn on the Floor Plan. Start drawing from the upper left corner and switch to the Arc by 3 points method on the Pet Palette to draw the curved edge, then switch back to the Straight Segment method on the Pet Palette to draw the rest of the segments. Finish the polygon at the same node in the upper corner.

picture6.PNG picture7.PNG picture8.PNG

The Dialog comes up to enter the perpendicular distance between the places of the two Profile Polygons of the Ruled Shell. Enter the thickness of the Wall with a negative sign (-500 mm in our example). You will see the reason for the negative sign when we rotate this Shell into a vertical position in a later step.

Step 4: Draw the other Profile Polygon

Then draw the other Profile Polygon of the Ruled Shell. Draw it the same way as the previous Profile Polygon, starting from the upper left corner, starting with the curved edge and continuing with the straight edges.

Note: it is important that you start both Profile Polygons at their equivalent nodes are draw in the same direction. This way you can guarantee that the correct nodes on the Profile Polygons will be connected to each other and the resulting Shell geometry will not be distorted.

picture10.PNG picture11.PNG picture12.PNG

This is a conditional step: note whether the body of the Shell was generated to the inside or outside of the Polygon you entered. If it was generated to the outside, then select the Shell and click the Flip button in the Info Box to flip the body to the inner side of its Profile Polygon.


Step 5: Free Rotate

Right-click with your mouse and from the appearing context menu select the Show All in 3D command.
In 3D, select the Shell you created and choose the Free Rotate command from the Pet Palette.


Rotate the Shell 90 degrees around the X axis so the Profile Polygons of the Shell will be rotated from the XY plane into the XZ plane (they will be in vertical planes parallel with the side surfaces of the Walls.

picture16.PNG picture17.PNG


Step 6: Set Trimming Body to Editable

With the Shell still selected, go to its Settings Dialog, and in the Model panel, set the Trimming Body field to “Editable”. Click OK to accept this change and leave the Dialog.

Activate the View\On-Screen View Options\Trimming Bodies menu command to make the Trimming Body of the Shell visible on the screen (if it is not set to be visible). It appears as a pinkish colored translucent body.
The Editable option set for the Trimming Body, the Trimming Body is now completely within the boundaries of the body defined by the Profile Polygons. We will be able to use this Trimming Body to cut out the needed shape from the Wall.


Step 7: Connect

Drag the Shell to the middle Polygonal Wall so the two Profile Polygon planes of the Shell coincide with the two sides of the middle Polygonal Wall, plus two sides of the Shell Profile Polygons are at the ends of the Polygonal Wall.


Now, select the middle Polygonal Wall, right-click and select the Connect\Trim Elements to Roof/Shell command. Note: the Shell should not be selected when issuing this command.


With the House with Dark Roof cursor shape, click on the body of the Shell to select it as the Shell to Trim to.
Click outside the body of the Shell to define the part of the Wall to remain after the cut.


Step 8: Elevate Wall Opening

Use the Elevate command to move the Wall Opening to its proper position.


Step 9: Change Element’s Layer

Go to the Layer Settings Dialog and create a Layer for Trimming Bodies (e.g. with the name “- Trimming Bodies” – the dash character at its beginning will make it appear at the beginning in he list of Layers in Dialogs and pop-ups). Set the status of this Layer to Hidden in the Layer Settings Dialog.


Move the Shell element to this new layer to hide it. All we have visible left in 3D now is the Wall with the Opening the Trimming Body of the Shell has cut out of it.


Step 10: Convert Wall to Polygonal Walls

Switch to 2D Floor Plan view and select the modeled Wall. Change its Geometry Method from Straight to Polygonal Type.


Use the Split command to cut this Polygonal Wall into three pieces.

Step 11: Set Floor Plan Fill Type

Modify the Floor Plan Fill Type of the middle piece to “Empty Fill” to correctly represent the Wall Opening.


  • Was this Helpful ?
  • 1   ​0

Related content

Show All in 3D

To show the entire model in 3D, regardless of any current selection, use the View > Elements in 3D View > Show All option; or use the same command from the context menu. This command’s shortcut is Ctrl + F5 . The full model display resulting from…

Trimming Body of Shell

This article will try help you to understand the usage of the Shell Trimming Body . create a spline choose Extruded Geometry Method and with Magic Wand create a Shell rotate the Shell with Free Rotate option place a Wall and see the…

Trimming in 2D

Trim function helps you to edit the existing elements quickly and easily in 2D and 3D view. Elements can be trimmed with Scissors Tool. One can cut off unneeded portions of Walls, Lines, Arcs etc., split them in two pieces or extend them to another…