Ptah

Ptah is a 3D level blockout editor for level designers, in a studio, a classroom or on your own. You block out a level to your engine's real player metrics, mark what every piece is for, drop in spawns and triggers, walk it at player height, and export a .usda file that opens in Unreal Engine or Unity with the geometry and the gameplay data intact.

Open Ptah

In your browser (nothing to install):

• https://levi-sterling.com/Ptah/
• https://smugsterling.github.io/Ptah/ (the same app)

Chrome and Edge save your level straight back to the file you opened. Firefox and Safari download a copy each time you save instead.

On a phone or tablet: https://levi-sterling.com/Ptah/mobile/ is the same editor laid out for touch. A phone that opens the main address is offered it.

• Phones: the tools sit in a bar under the view, and the panels (Inspector, Hierarchy, Metrics, Reference, More) in a sheet below it. Tap a tab to open it, and tap it again to close it.
• Tablets: the desktop arrangement, with bigger buttons.
• Camera: drag one finger on empty space to orbit, use two fingers to pan and pinch, and tap to select. Drag the gizmo's arrows to move, rotate or scale.
• Walk: the left stick moves you. Drag anywhere else on the view to look. Jump, Crouch, Run, View and Exit are buttons.
• Files: Open reads a .usda from Files or Downloads, and Save downloads one.
• What's missing: a phone has no box select or Ctrl-click, so you edit one object at a time. It has been tested on emulated iPhone, Android and iPad screens; real iOS Safari needs iOS 15.4 or newer.

As a desktop app: download the latest release from the Releases page.

Your computer	Download
Windows	Ptah-<version>-win-x64-setup.exe to install, or …-portable.exe to run without installing
Mac (Apple Silicon)	Ptah-<version>-mac-arm64.dmg. On an Intel Mac, use the browser version
Linux	Ptah-<version>-linux-x86_64.AppImage, or the .deb for Ubuntu and Debian

The desktop builds are not code-signed yet, so the first launch shows a warning:

• Windows: "Windows protected your PC". Click More info → Run anyway.
• Mac: right-click the app and choose Open, then Open again.

Without the internet: if you have a copy of this repository (Code → Download ZIP on GitHub) and Node.js 22 or newer, double-click the launcher in the folder:

• Mac: Launch Ptah.command
• Windows: Launch Ptah.bat
• Linux: launch-ptah.sh or Ptah.desktop

It opens Ptah in your browser. Leave the small terminal window open while you work.

Ptah never sends anything anywhere. There are no accounts, no tracking and no network requests; your level stays on your computer.

Your first level

1. Pick the template you are building for. Ptah asks once per new level: Unreal Engine Third Person or First Person, or Unity Third Person or First Person (Starter Assets). It loads that template's player size, eye height, speeds, jump and step height, and sizes cover, doorways and corridors from them. The file remembers your choice; Metrics → Change switches it later.

   

2. Block out.

   • Press C and click the grid to place a cube. Y, S, P, V and T place a cylinder, sphere, plane, wedge (ramp) and stairs.
   • W, E and R move, rotate and scale.
   • Type exact sizes and positions in the Inspector on the right.
   • The Presets menu places cover, doorways, corridors and step runs already sized to your template.

3. Say what each piece is. Pick an intent swatch in the Inspector: Floor, Wall, Cover, Blocker, Water, Hazard, Interactive or Placeholder. The colour is the intent, and it travels with the file.

4. Add gameplay markers. Press K (choose the kind in the Marker menu) to place a Player start, enemy Spawn, Cover point, Objective or Trigger volume. Add tags in the Inspector.

5. Walk it. Click an empty spot in the viewport, then press Tab:

   • WASD walk, Shift run, Space jump, hold C to crouch, the mouse looks around.
   • V switches between first and third person.
   • Esc returns to the editor.

6. Save with Ctrl+S (Cmd+S on a Mac). The file is a .usda; see Taking your level into an engine.

What you can do

Building

• Primitives: cube, cylinder, sphere, plane, wedge (ramp) and stairs. Click to stamp one. With the cube, drag out its footprint instead: the press is one corner and the release the other, snapped to grid lines while Snap is on, with the size shown as you drag. Holding Shift inverts Snap for the drag, as it does everywhere: free with Snap on, snapped with it off. The other primitives move with the drag before you let go. Stairs have an editable step count.
• Extrude (X): drag a face of a block to lengthen it from one end; the opposite face stays put.
• Groups: Ctrl+G groups the selection and Ctrl+Shift+G ungroups. Drag rows in the Hierarchy to reorder or nest them; objects stay where they are in the world. The one exception is refused rather than done: a turned object can't leave a group scaled unevenly (or join one), because no position, rotation and scale could keep its shape. Give the group an even scale first.
• Selecting several objects: Shift+click, Ctrl+click, drag a box on empty space, or Ctrl+A. The gizmo then moves, rotates or scales them together.
• Editing numbers: with several objects selected, the Inspector shows the shared value (or a dash when they differ). Type +=64, -=8, *=2 or /=2 to change each one relative to its own value. The center / base toggle beside Position makes the Y field read the bottom of the object.
• Snapping: G snaps to the grid, and holding Shift flips snapping while you drag. Shift+G snaps faces flush against neighbouring blocks.
• Measure (M): click two points to read the distance in units and metres.

Designing to metrics

• Metrics panel: the numbers your level is built to: player height and width, eye, crouch and step heights, camera field of view, speeds, jump height and distance, and the cover, door and corridor sizes. Change any of them and the profile becomes Custom; Reset goes back to the template you started from.
• Height ticks (H): every Player start and Spawn capsule shows marks for player, eye, crouch, cover and step height, so you can drop one beside a block and read it like a ruler.
• Third person (V while walking): a mannequin at your template's character height, with a camera behind it like the engine templates. Third-person templates start in third person.

Planning

• Notes (N): pin a note to a surface. Its title and text are saved in the file.
• Reference image: load a floor plan or paper sketch in the Reference panel (or drop an image on it), set its width, rotate, move and dim it. It is saved inside the level file.
• Grid: the Grid field sets the cell size; the Ground field sets how wide the grid is drawn (it grows on its own if you build past it). The slider dims the grid so a reference image shows through.

Comfort

• Themes: the picker at the right end of the top bar recolours the bars and panels. Pick Ptah (the default), Catppuccin, Rosé Pine, Light, Light HC or Dark HC; the two HC themes are high contrast. The viewport and your level never change colour: intent colours are saved in the file and go to the engine. Every theme meets WCAG 2.2 AAA for body text and AA for all other text, and Ptah remembers your choice. Palettes: Catppuccin Mocha, Rosé Pine and GitHub's Primer Light, Light High Contrast and Dark High Contrast, all MIT-licensed (notices).

Safety nets

• Undo everything with Ctrl+Z: placing, moving, grouping, metrics and reference changes alike.
• Autosave: Ptah keeps a recovery copy a few seconds after every change. If the browser or computer crashes, reopen Ptah and a bar offers your work back. In a browser without a Save dialog (Firefox, Safari) a Save is a download, so Ptah keeps the copy until you tell it downloads arrive: dismiss the bar that offers a downloaded copy once and it stops keeping them. If the browser gives Ptah no storage at all, it says so once.
• Safe saves (desktop): the previous version of your file is kept next to it as <name>.bak, and a crash during a save never leaves a half-written file.

Keyboard reference

Key	Action
Q	Select, with no gizmo
W / E / R	Select with the move / rotate / scale gizmo
Esc	Back to Select (keeps the current gizmo) and clear the selection. Cancels a drag or placement in progress, and leaves walk mode
C / Y / S / P	Place cube / cylinder / sphere / plane
V / T	Place wedge (ramp) / stairs
N	Place a note
K	Place a marker (the kind last picked in the Marker menu)
X	Extrude: drag a face
M	Measure between two points
G	Grid snapping on / off
Shift (held)	Flip snapping while dragging
Shift+G	Face-to-face snapping on / off
H	Height ticks on marker capsules
F	Frame the selection (or the whole level)
1 / 3 / 7 / 0	Front / right / top / free camera
Tab	Walk mode, starting at the selected Player start. Works when nothing else has keyboard focus; otherwise use the Walk button
In walk mode	WASD move, Shift run, Space jump, hold C to crouch (or Ctrl in the desktop app), mouse look, V first / third person, Esc or Tab to leave
Shift+click or Ctrl/Cmd+click	Add to or remove from the selection
Drag on empty space	Box select
Ctrl+A	Select all
Ctrl+G / Ctrl+Shift+G	Group / ungroup
Ctrl+D	Duplicate
Del / Backspace	Delete
F2	Rename (or double-click a Hierarchy row)
Ctrl+Z / Ctrl+Shift+Z (or Ctrl+Y)	Undo / redo
Ctrl+S / Ctrl+Shift+S	Save / Save As
Ctrl+O	Open
Ctrl+N	New (desktop app; in a browser use the New button, because browsers keep Ctrl+N for a new window)
Middle mouse drag / right mouse drag / scroll	Orbit / pan / zoom the camera
Touch: one finger / two fingers / pinch / three fingers	The current tool (place, select, box select) / orbit / zoom / pan

On a Mac, use Cmd wherever this table says Ctrl.

Hierarchy panel: the arrow keys move through the list (Shift extends the selection). Left and Right collapse or expand a group. Space adds or removes a row from the selection, Enter (or a double-click) renames, and Shift+H hides or shows. Alt plus the arrow keys reorders, and Alt+Right moves an object into the group above it.

Units and scale

• 1 unit = 1 cm. A 180-unit capsule is a 180 cm player. Unreal uses the same scale; Unity converts to metres on import.
• The default grid cell is 64 units, with a heavier line every 4 cells.
• An object's Size in the Inspector is its width, height and depth in units. Bounds is the box around it and its children, which differs from Size once something is rotated.
• A child inherits its parent's scale. To organise objects without stretching them, group them (Ctrl+G) rather than parenting them under a scaled block.

Taking your level into an engine

Save your level, then import the .usda file:

• Unreal Engine 5: enable the USD Importer plugin, then import the file or place a USD Stage actor.
• Unity: use Unity 6.3 LTS with the USD Importer package (com.unity.importer.usd), then copy the .usda into your project's Assets folder.

The geometry arrives with its intent colours. Markers, including triggers, arrive as named empty objects that draw nothing. Ptah's engine tools turn them into real Player starts, spawn points and trigger boxes: in Unity the Ptah Markers package (installed from Package Manager with a Git URL), in Unreal a Python script in tools/unreal/.

docs/importing.md walks through both engines step by step.

Things to know

• Saving in the browser: Chrome and Edge save in place. Firefox and Safari download a copy each time. The first download in Safari may ask for permission, so check your downloads folder after your first save.
• Opening other people's USD files: Ptah reads files from Blender, Maya, Houdini and the engines, but only the geometry and transforms from a single file. References, payloads and animation are not imported. A file that is Z-up or not in centimetres comes in inside one group that converts it; ungroup it (Ctrl+Shift+G) to apply the conversion to the objects.
• Walk mode is a scale check, not a game: you collide at knee height with a body as wide as the profile's capsule. Walls, posts and gaps narrower than the body stop you, however thin they are; risers up to the step height and ramps up to 45° carry you up, as in Unreal and Unity. There is no head collision: crouching lowers the camera to the crouch height, but letting go of C under a low ceiling stands you up through it. The third-person mannequin crouches as a person would, so its head can show through a ceiling the crouch height clears. The jump shows height and distance rather than game-feel.
• Snapping uses bounding boxes, so a rotated block snaps by the box around it, not its tilted faces.
• Extrude changes a block's size. It cannot cut a doorway out of a wall or extrude a sloped face; build doorways from blocks or use the Doorway preset.
• Scale and rotation together: a rotated child under a group that is stretched unevenly will shear. Unreal and Unity do the same.
• Keyboard-only use: placing a new object and orbiting or panning the camera need a mouse or trackpad. Once objects exist, selecting, editing (through the Inspector's fields), renaming, grouping and organising the Hierarchy all work from the keyboard, with the camera presets 1, 3, 7, 0 and F.

Help and feedback

Found a bug or have an idea? Open an issue on GitHub. What changed in each version is in CHANGELOG.md.

Ptah is made by Levi Sterling and released under the MIT licence. Developers: building, testing and releasing are covered in CONTRIBUTING.md.