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Wind Sway

App: apps/wind_sway_demo/

Demonstrates the global frame-uniform block (engine PLM-236 / ADR 0072) — the universal prerequisite for animated shaders (grass/tree wind sway, water waves, moving clouds). The engine binds a { time, delta, frameIndex, wind } block at set 0, binding 4 every frame; a shader reads plume3d_time() and the wind and animates on its own, with no per-draw uniform plumbing.

Run from root

Section titled “Run from root”
Terminal window
% ./plume3d wind_sway_demo

A green quad’s top edge sways and its colour pulses — both driven by the frame clock. The demo takes two screenshots ~0.7 s apart; because the clock has advanced between them, the two frames differ, proving the frame time reaches the GPU.

What it does

Section titled “What it does”

  • Builds an NDC quad with Graphics.newMesh and a shader loaded from shaders/wind.

  • Sets a global wind once, which the engine folds into the frame block:

    Graphics.setWind(1.0, 0.0, 0.0, 1.0)   // blow along +X at unit strength

  • The shader #include "plume3d.slang" and sways the tip by the frame clock × wind, then pulses its colour with time:

    float sway  = sin(plume3d_time() * 2.0 + p.x * 3.0) * plume3d_windStrength() * 0.25 * tip;
    float pulse = 0.5 + 0.5 * sin(plume3d_time() * 3.0);

See Graphics.setWind and the frame-uniform note on /api/graphics. Screenshot-verified (two frames differ).