GameKeyControl

GameKeyControl

A held-key spaceship demo, ported from NGL9Demos/AdvancedGameKeyControl. This one's about held keys rather than key presses -- Up/Down/Left/Right/R can all be down at once, and every combination has to move the ship sensibly (Up+Left should be a diagonal, not whichever branch happened to run last). Rather than a tree of if/elif checks, game_controls.py's MOTION_TABLE is a flat 32-entry lookup table indexed directly by the held-key bitmask, so the "what does this combination of keys do" question is answered once, offline, instead of every frame.

Space starts and stops recording every frame's bitmask to a KeyRecorder; P replays a recording back over the ship's original starting position; S/L save and load a recording to/from a .kp file. The maths and the recorder live in game_controls.py, shared with the WebGPU version of this demo -- see that file for move_ship(), ship_transform(), and KeyRecorder. This .kp format is a Python-native text encoding (one decimal integer per line), not the raw byte stream the original C++ AdvancedGameKeyControl writes for each frame, so a recording made by this port won't load in the C++ demo or vice versa -- it's only interchangeable between this port's own OpenGL and WebGPU entry points.

There's no mouse camera control here at all, which is unusual for this repo -- the C++ source never wires up a mouse handler, so this port doesn't either. The camera is one fixed look_at, set once in initializeGL.

It also runs on two independent timers rather than this repo's usual one, again matching the source: a 15ms timer samples the held keys and steps the ship, and a separate 30ms timer only triggers a redraw. Sampling input faster than you redraw is a reasonable thing to want in a game loop, and it's the whole reason this demo has two timers instead of one.

Controls

• Arrow keys : move the ship (held, not pressed -- diagonals work)
• R : rotate (held)
• Space : toggle recording
• P : toggle playback
• S / L : save / load a recording (.kp file)
• Esc : quit

WebGPU version

main_webgpu.py needs no reinterpretation for this demo's actual teaching point (the bitmask-indexed motion table and file-based record/playback are plain Python/Qt, identical on both backends) -- the only backend-specific work is drawing the ship and the HUD. ncca.ngl.WebGPUMesh uploads the same parser-only OBJ data used by the OpenGL version, and a small hand-rolled flat WGSL shader (GameKeyControlShader.wgsl) stands in for the OpenGL side's built-in nglColourShader equivalent. A recording saved from either backend loads and plays back correctly in the other -- the .kp format and the KeyRecorder class are shared, unmodified, from game_controls.py.