In this lesson, you will learn how to build a spiral staircase using polygon Boolean and a bend deformer.

This lesson highlights how deformers can be used to enhance the modeling process



Select Create > Polygon Primitives > Cube.

In the Channel box, set the cube's width to 5 and its Subdivision Depth to 10.

Move the cube so that it is sitting on the ground plane.

This cube will act as the first tread of the staircase. The subdivisions will help ensure a smooth bending later.



Select Edit > Duplicate > options.

Set Smart Transform to On. This option will allow you easily create multiple duplications. Click the Duplicate button.

In the side view, Move the duplicated cube up and to the right. This will be the second tread.

Note: Do not de-select the cube. If you do, Smart Transform will lose the offset information it needs to produce the duplicates created in the next step.



Press Ctrl - d. This will create another duplicate that is offset by the same amount as the second tread.

Press Ctrl - d eight more times to create the treads of the stair.

You now have several cubes that are all separate shapes. You will need to use polygonal Boolean to create a single surface for the stair.



Select the first two treads. Select Polygons > Booleans > Union. They are now one shape.

Note: you can only join two polysets at a time. Now you have to add the other treads.

Press the shift key then add the third tread to the selection. Press the g key to repeat the Boolean union. Repeat these steps until all the treads are combined into a single polyset.

The various Booleans have added history to the staircase that is not needed. Select the polyset then select Edit > Delete by Type > History to remove the extra input nodes.



Select Create > EP Curve Tool. In the side view, draw a single span curve where you would want to place a handrail.

Select Edit Curves > Rebuild Curve - options. Set Number of Spans to 20. Click Rebuild. This will add enough CVs to ensure a good bending when you add the deformer later.

In the top view, place one curve at one side of the stair and then duplicate the curve to create a second handrail at the other side of the stair.

Note: You have built a curve for the handrail so that you can extrude a profile after the bending. Building the handrail as a surface would add too much distortion after bending.



Select the curves and the stair polyset.

Select Deform > Create Nonlinear > Bend - options. Set Curvature to 4 then click on the Create button. This gives you a sideways bend that doesn't look like a staircase.



In the Channel box, set the bendHandle's rotateX to 90. This reorients the deformer to create more of a stair shape.

With the Move tool, move the bendHandle along the X axis to widen the bend. Now the handrail curves and the treads are bending nicely into a spiral stair.



In the Channel box, click on the bend Input node. Now select the Show Manipulator tool. You can drag on the curvature handle to adjust the amount of curve in the bend.

Note: You can also animate the bending of the stair by setting keys on the curvature attribute.



To create the handrail surfaces, create a primitive circle and scale it to a reasonable radius.

Select the circle and then one of the handrail curves. The path curve for an Extrusion must be picked last.

Select Surfaces > Extrude - options. Set Result Position to At Path and Pivot to Component. Click Extrude and the handrail will be placed on the handrail curve. Repeat for the other handrail.

Tip: If history is maintained as you extrude then you can later select the circle and scale it. The two handrail surfaces will update to show the new profile radius. This lets you evaluate the profile size after extruding to see it in context.


The bend deformer has made it easy to build a spiral staircase with handrails. You can now delete history or choose to keep it around in case you want to update some part of the model.