Stair Path Generator

With the Spline Stair Path Generator you draw a spline, and PolyBash builds a walkable corridor along it. Sections that rise become stairs, and sections that stay level become a flat path. The generator also adds side walls, openings with tunnels, edge trims, railings and colliders.

This page documents every section of the inspector. The page Spline Generators Overview explains the parts that both generators share, such as the build cycle, the stage system and the Info section.

How the spline becomes stairs and a path

The spline knots divide the corridor into sections, and one section spans the distance between two knots. The generator classifies each section with the fields of the Shape section.

A stair section receives the smallest step count that respects both limits. The generator divides the height by Max Step Height, divides the length by Max Step Depth, and then uses the larger of the two results. The step size that results from that count is rarely exactly your minimum or your maximum. The count keeps each step at or below Max Step Height, and it keeps the mean step depth at or below Max Step Depth. A step can be lower than Min Step Height or shallower than Min Step Depth. The generator compares the step height and the mean step depth of each section with the limits and their tolerance. It reports each breach as a warning in the Info section. A message names the section, the value and the accepted range. The message counts the sections from 0, so "Section 0" is the node Section-01.

A flat section receives the smallest piece count for which no piece is longer than Max Path Depth. A larger value lowers the polygon count of the path, and a curve becomes coarser. To keep the texture scale while you change that value, set Path Uv Mode to Arc Length.

To convert a section from a path into stairs, raise or lower one of its two knots. To convert stairs into a path, level the two knots.

Quick start

1. Create the generator, as Add a generator to a scene describes.
2. Draw a spline with at least three knots, and raise the middle knot.
3. Assign a material to Default Material.
4. In the Shape section, adjust the step limits, and edit the corridor widths in the Per-Knot Offsets foldout.
5. In the Walls section, select Add Walls.
6. In the Railings section, select a Side.

After a change outside the inspector, such as an edit of a material, select Regenerate.

Pieces

The generator builds its own meshes, and it needs no further asset. The Pieces section holds every parameter of those meshes.

PolyBash generates a set of template pieces from these parameters, and each template carries a deformation lattice. During the build, the lattice deforms each template along the corridor, so one template adapts to every step size, corridor width and curve. The parameters describe only the template, and the real size of a step comes from the spline and from the Shape section. The build only moves and rotates the balusters and the newels, so they keep the size of their parameters.

Include groups

Edges and rails need the stair pieces and the path pieces as a reference for their offset. As a result, PolyBash includes both groups automatically, and a note reports that behavior. The parameter groups appear only for the groups that you include, with two exceptions. Core — Stairs & Path always appears, and Edges also appears while Include Rails is selected.

Core — Stairs & Path

The UVs foldout holds Uv U Min, Uv U Max, Uv V Min, Uv V Max and Uv Pad. These fields select the region of the texture that the step bodies use. The path pieces use only Uv U Min, Uv U Max and Uv Pad. Their V coordinate spans 0 to 1 over the whole set of path pieces. Uv Pad removes a border inside that region, so that the pieces never sample outside it.

Edges

Rails

Posts

Arch Frame

Validation

The section reports every problem below the fields. An error blocks the build, and a warning describes a result that is probably unwanted. The most frequent messages concern a value of 0 or a side count below 3. A warning also appears when Edge Height or Rail Height is equal to Rise or lower.

A configuration without any group produces the warning "No piece groups enabled — nothing to generate", and the build stops.

Materials

An empty material field falls back to Default Material, at the top of the inspector.

While Add Walls is selected, the sidewalls of the steps use Wall Material, and their texture continues the texture of the wall.

Shape

Step

When the steps of one section differ in depth, select Constant Slope. Such steps appear, for example, on a spline that curves up and down between two knots.

Path

Dimension

The foldout Per-Knot Offsets holds one Left value and one Right value per knot, and the build uses only these values. A knot that you add at the end of the spline receives the two values above. Reset All To Global restores those values at every knot. Each value belongs to a knot index, so an insert or a deletion inside the spline shifts the widths of the knots after it. After such a change, verify the widths of the following knots. You can also drag the cyan handles in the Scene view to edit the same values. Hold Shift to move both sides at the same time.

Walls

A wall stands on each side of the corridor. Its top follows the corridor surface, and its bottom sits at the wall floor of each knot.

An override accepts three values. None and On build the wall while Add Walls is selected, and Off removes it. Use Off to open one side of the corridor toward a room.

Per-Knot Base Offsets

This foldout holds the depth of the wall floor below each knot, in meters. A value of 0 places the floor at the knot itself, so the wall has no height there.

The first build sets each depth so that every floor sits at the height of the lowest knot. As a result, the lowest knot starts with a depth of 0. A knot that you add at the end of the spline receives the depth that puts its floor at the current lowest floor. When you move a knot, its depth stays the same, and its floor moves with the knot.

While Add Walls is selected, an orange handle sits below each knot in the Scene view. The toggle Wall-Floor Base Handles in the Scene Gizmos section controls these handles. Drag the handle up or down to change the depth of that knot.

Select Reset All To Lowest Knot for a corridor that must stand on flat ground.

Because each depth belongs to a knot index, select a reset button after you insert or delete a knot inside the spline.

Wall Openings

The foldout Wall Openings holds one card per opening. Add Opening appends a card, and Remove deletes one.

The three frame fields need Add Tunnel, because a frame surrounds the entrance of a tunnel.

Two fields below the cards apply to every opening:

• Opening Min Clearance — the smallest vertical gap between the ceiling of an opening and the top of the wall, in meters. The default value is 0.1, and it prevents an opening that cuts through the upper edge of the wall.
• Arch Frame Material — the material of the frame blocks. An empty field falls back to Default Material.

The toggle Wall Opening Handles in the Scene Gizmos section controls the handles of the openings in the Scene view. The handles appear while Add Walls is selected.

• Drag the sphere on the spline along the corridor to change T.
• Drag one of the two cubes along the spline to change Width (m). The width grows on both sides, so the center of the opening stays in place.
• Drag the cube above the sphere up or down to change Height (m).
• The label above each opening shows its index, its width and its height.

Colliders & Physics

The Ramp foldout replaces the stepped collider with a smooth slab, so a character slides along the staircase instead of stopping at each step.

Stair Edges

This stage lays trim pieces along the boundaries of the corridor, and it produces nothing until an entry has a category. The foldout Edge Entries holds one card per entry, and each card title carries the index of the entry. Add Edge appends a card, and Remove deletes one.

After you add a card, select a Category, because a new card starts at (None).

A category that the pieces do not offer shows the suffix "(not in catalog)", and that entry produces nothing. For example, Handrails shows that suffix after you clear Include Rails.

Four fields below the entries apply to every entry:

For the usual result, add two entries: one entry with DefaultTrim for the trim at the foot, and one entry with Handrails for the rail.

Railings

This stage places the vertical posts: the balusters along the corridor, and the newels at the two ends of each staircase. While Side is None, only the sections with an override On receive posts.

The foldout Per-Section Post Overrides holds two rows per section: one row for the balusters, and one row for the newels. Each row overrides the left side and the right side. None follows Side, On forces the posts, and Off removes them.

Generated output

The generator creates one node per section, such as Section-01, and the names of the meshes describe their content.

Two stages emit their own roots, and each node below them carries the number of its section as a suffix:

• Edges holds one node per entry and section, such as Edge_0-00 for entry 0.
• Railings holds up to one Balusters node and one Newels node per section, such as Balusters-00 and Newels-00.

The suffix counts from 00, but the section nodes count from 01, so Balusters-00 belongs to Section-01.

Troubleshooting