What is a Revit mass? What is its purpose? Why does Revit automatically hide them in all views? One may assume masses are irrelevant due to their hidden nature and limited utilization. Not true!  Revit masses are incredibly useful! In some instances, they are necessary to achieve a desired form.

What is the purpose of the mass function in Revit?

It is possible to use Revit for years and years and never touch the mass function. After all, Revit hides these by default, so they must not be very important.  Right?  Wrong.  Masses serve an integral role within the Revit user interface.

First, masses provide the user the ability to quickly explore various design options in many shapes or sizes early in Schematic Design. They provide free-flowing shapes that enable users to push and pull elements with ease and flexibility. If a designer is approaching an empty canvas, then they may quickly manipulate as many shapes as possible to develop ideas at a very high level. As the concept develops, she may introduce dimensions to incorporate accurate scale. This is true for massive skyscrapers, a piece of furniture, and everything in between.

Not only are masses helpful in the early stages of design, but they are also required to produce free form shapes like compound curves. Revit already includes a highly intelligent system to draw and document a wall. One may incorporate materials and thicknesses. Designers may indicate height and width. If the wall is not a rectangle, “Edit Profile” may be used to create any shape that occupies a single plane, assuming that plane is vertical.

Recent versions of Revit have built on this platform to provide additional functionality.  For example, Revit 2021 introduced Slanted Walls, which allow the user to define the angle variant from true vertical. Revit 2022 introduced the Tapered Wall which allows the wall to vary in thickness over the height of the wall. Neither of these were possible prior to the release of 2021, unless masses were used.

These new advancements are wonderful, but what if the intent is incorporate a compound curve into the plane of a wall? Well, out of the box Revit walls may not achieve this shape yet. However, with the use of Revit masses, compound curves or literally any shape is possible. Not only is it possible with the mass itself, but the complex shape may be applied to a traditional Revit wall, which holds all the parametric information.

Place Mass

Revit provides an “Out of the Box” command for those who need basic massing building blocks that can be manipulated quickly with limited articulation. Perhaps a designer is exploring a neighborhood layout, or providing a campus master plan? They may use the “Place Mass” command, which will direct the user to Autodesk’s standard mass shapes.

The Imperial Library contains about 20 families (.rfa) of standard shapes, including a box, cylinder, sphere, pyramid and simple gable house, among others. Once these families are loaded into the Revit project (.rvt), the user may move, rotate or adjust the scale of each component to quickly to represent the features within the schematic study.

As previously noted, the mass category is hidden in all views by default. This is not an accident or indicative of importance, or lack thereof. The mass category is hidden by design because it is not the intent for mass elements to be included within Revit documentation. It is intended as a vehicle to form complicated geometry, which is then applied to native Revit elements, like walls, roofs and floors.

A user may unhide the mass category in any view, which would show the mass elements permanently. Alternatively, a designer may use the “Show Mass Forms and Floors” function, which shows the mass category in all views temporarily. When toggled off, the category defaults back to “Hidden” in all views.

Join Geometry

As one quickly moves and manipulates many masses around in the workspace, it is helpful to define the Work Plane. If the site has many levels, for example, the designer may simply select the Placement Plane of each element as he clicks to place them within the design space. The Placement Plane can be any predefined Level that has been modeled in the file. Alternatively, he may utilize “Place on Face” if a mass sits on another mass or element.

If the two or more masses collide into each other and overlap, “Join Geometry” may be used to simplify the geometry. This command will cut one shape out of the other and provide a hard joint where they meet. In addition, materials may be applied to the shapes. This is especially helpful during early stages of design. The designer is not required to make a new Wall Type and define all the materials within the wall assembly, he may simply apply a material to the entire shape. Obviously, this would not be proficient as one rolls into Design Development or Construction Documents, but in Schematic Design, it provides incredibly useful insight as to how the overall palette of materials will interact with each other.

In-Place Mass

Often, “Out of the Box” shapes are not sufficient to accurately reflect the design intent. A more precise shape may be required. For this, Revit utilizes the “In-Place Mass,” which allows the user to draw any shape to define a single plane. After the flat shape is drafted, the “Create Form” command will extrude the shape into a 3-dimensional object.

Specific dimensions may be used to provide exact scale, or one may push and pull the planes if approximate size is sufficient. Not only is each plane accessible for adjustment, but each edge may also be manipulated. This maneuver will update every plane that meets that specific edge. Not only are the planes and edges flexible, but every single 3D point on the shape may be selected and moved in any direction as well. This includes movement both in the X-Y Plane as well as the Z direction. So, any shape is possible with this level of flexibility.

Perhaps the design does not include a 3-dimensional object? Maybe the design is inspired by a single plane that undulates with various compound curves? For these applications, the designer may simply draft a single line or curve. The “Create Form” command will produce a plane from the unclosed line or lines. Afterward this plane may be pushed or pulled for a rippling surface, like a flag in the wind, for example.

Mass Form Types

As previously noted, the “Create Form” command is the vehicle that transforms a line or plane into a 3-dimensional object. Revit includes six basic methods as depicted below:

1. Extrusion – Draw a shape (called profile), then Create Form. An extrusion is produced.
2. Blend – Draft two profiles on different planes, then Create Form. A blend is created that connects the two profiles and interpolates the two shapes vertically.
3. Loft – Sketch three or more profiles on separate planes, then Create Form. A loft is created that connects all the profiles and interpolates between all the shapes vertically.
4. Revolve – Produce a 2-dimensional shape and an axis of rotation, then Create Form. The shape will be revolved around the axis. If the line of axis aligns with an edge of the shape, the revolve will be a solid circular shape. If the line of axis is offset from the shape, then a round hole will be in the center of the circular shape.
5. Sweep – Outline a profile and a path, then Create Form. The profile will be extruded along the path.
6. Swept Blend – Draw a path, and a profile at both ends of the path, then Create Form. The profiles will be extruded along the path, and the shapes will be interpolated between each other.

Edges and Profiles

After the initial form is created, additional access points may be required to achieve the design intent. For instance, an extrusion or blend may be a sufficient starting point to accurately reflect the top and bottom of an object. But, what if a certain amount of undulation is required between the top and bottom planes? For these cases, we have edges and profiles.

Just as the top and bottom of a blend are already Profiles, the “Profile” command will add additional profiles at any height within the existing shape. In essence, the extrusion or blend will become a Loft. This allows the designer to edit each profile individually, which will in turn have greater control over the waves and ripples of the object.

If the object requires the ability to manipulate in the vertical direction, then an edge may be useful. This applies a single vertical edge that connects multiple profiles. Users may utilize the full length of the edge or the point at either end to push/pull as required.

Divide Surface

The design elements are in their proper position. The overall shape of each component is roughly the correct form. The team is moving through Schematic Design nicely, but not quite ready to jump into Design Development. First, it would be nice to study the articulation of each face prior to producing actual Revit Walls.

For this design effort, the “Divide Surface” command comes in handy. This tool unlocks several other tools that enable the designer to study patterns or forms on any given plane. Grids may be placed on the face in both the U and V direction. The spacing, scale, rotation, justification and offset of these grids may be quickly modified via instance parameters. Not only is grid manipulation an option, but the designer may also start to incorporate patterns within the grid. These patterns may or may not make their way to the final design, but the exploration of these designs can be studied and evaluated in a fraction of the time.

Floors and Roof

The time has come to wrap up Schematic Design and move into Design Development. All components are properly arranged and drawn to scale. However, when a floor plan is created, the only thing that is shown is a translucent box. The same applies to sections. The overall height and shape are accurate, but it is just a diagrammatic frame. No indication of walls, roofs or floors.

Revit offers tools to seamlessly make this transition from SD to DD. Upon selection of a Mass element, a designer may execute the “Mass Floors” command, which will create horizontal planes at any or all selected Revit Levels. After the Mass Floors are created, native Revit Floors may be created with all inherent parametric information embedded. These are modeled via the “Floor by Face” command available in both the Architecture and Massing & Site tabs. Similarly, native Revit Roofs can be created via the “Roof by Face” command.

Walls

What about native Revit walls? They will not twist and turn like the mass, correct? No, they will not twist and turn by themselves. However, with the help of masses, native Revit walls can be any shape that was formed with the mass function. Simply use the wall command from the Architecture tab and select “Pick Faces” from the draw panel and select the desired face on the mass.

Alternatively, go directly to the “Wall by Face” command within the Massing & Site tab. This allows the user to model native Revit walls with all parametric information from the Wall Category and morph to any shape that was designed via the Revit Mass.

Mass Modifications

Design Development is now 50% complete.  All walls, roofs, and floors have been modeled from the mass element.  A decision was made to slightly rotate one of the Profiles by 5 degrees.  Or maybe a huge revision was ordered to manipulate many faces of the mass.  Does this mean the Revit elements should be deleted and re-drawn?  No.  “Update to Face” allow the designer to update any Revit element to realign with the revised mass.

Conclusion

Revit Masses are incredibly useful, yet highly underutilized. In some cases, a mass can save hours of time, while other instances a mass is required to achieve the desired result. Begin to incorporate Masses into your workflow today!

Matt Linn, AIA, LEED AP, ACI

Sr. AEC Technical Specialist

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