Orkuncakilkaya
9dff8f21bd
The grass had a gust built from two sines; the trees had no gust term AT ALL, only a per-instance wobble. So the meadow rippled and the canopy above it swayed to an unrelated rhythm, and nothing ever crossed the valley. wind.glsl is prepended to every stage (programs.ludic, and shaders.ludic for the SPIR-V build) so grass, crowns and water read the same field at the same world position. It declares no uniforms on purpose: u_time and u_wind already exist in several of those files and redeclaring them is a compile error in whichever stage includes both. The wavelength is what made it work. At 0.030 the front was 209 m crest to crest - longer than the meadow you can see - so the whole frame sat in one phase and the gust read as everything breathing together. At 0.085 it is 74 m and a front crosses a view in a couple of seconds. R3D_DEBUG_WIND=1 paints the field on the ground. It is the only honest way to show a gust in a still image, and two shots 0.3 s apart move by 39/255. 400 frames: GL 6.9 s, VK 7.2 s. Backends agree to 0.68/255. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
44 lines
2.7 KiB
GLSL
44 lines
2.7 KiB
GLSL
// ---- ONE WIND, and everything in the valley is moved by it ----------------------------------
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//
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// Before this the grass had a gust term built from two sines and the trees had NO gust at all -
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// just a per-instance wobble - so the meadow rippled and the canopy over it swayed to an
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// unrelated rhythm. Nothing ever crossed the valley. A real gust is a WAVE: you watch it come
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// over the grass, it reaches you, and it goes on into the trees behind you, and that single
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// fact does more for "this place is alive" than any amount of extra detail.
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//
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// It is prepended to EVERY stage (programs.ludic), so the grass's vertex shader, the crown's
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// vertex shader and the water's fragment shader all read the same field at the same world
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// position and cannot drift apart. No uniforms are declared here on purpose: u_time and u_wind
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// already exist in several of those files, and redeclaring them would be a compile error in
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// whichever stage happened to include both. The caller passes what it already has.
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// The prevailing wind down the valley. Maroon Creek runs roughly north-east, and a mountain
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// valley funnels its wind along itself rather than across.
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const vec2 WIND_DIR = vec2(0.86, 0.51);
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// 0 = still, 1 = the middle of a gust. Mostly low with fronts travelling through it, because
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// real wind is gusts separated by calm and not a constant shaking.
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float windGust(vec2 xz, float t) {
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float d = dot(xz, WIND_DIR);
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float across = dot(xz, vec2(-WIND_DIR.y, WIND_DIR.x));
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// three scrolling bands: a fast narrow front, a slow broad swell, and a slight variation
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// along the front so it does not arrive as one straight wall
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// The wavelength has to fit INSIDE a view or nothing is ever seen to travel: at 0.030 the
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// front was 209 m from crest to crest, longer than the meadow you can see, so the whole
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// frame sat in one phase and the gust read as everything breathing together. At 0.085 it is
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// about 74 m and a front crosses a normal view in a couple of seconds.
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float g = sin(d * 0.085 - t * 2.6)
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+ 0.65 * sin(d * 0.022 - t * 0.85 + 1.7)
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+ 0.40 * sin(across * 0.040 - t * 0.55);
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// tighter than a plain smoothstep either side: gusts with calm between them, not a wobble
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return smoothstep(-0.10, 1.35, g);
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}
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// What a plant actually does: a small constant tremble it always has, plus the gust, which is
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// most of the motion. `stiff` is how much the plant resists - grass near 0, a spruce trunk near
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// 1 - so the same field moves a blade a long way and a bole hardly at all.
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float windSway(vec2 xz, float t, float phase, float stiff) {
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float tremble = sin(phase) * 0.6 + sin(phase * 2.3 + 1.0) * 0.4;
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float gust = windGust(xz, t);
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return (tremble * 0.30 + gust * 1.35) * (1.0 - 0.85 * stiff);
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}
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