67 lines
1.9 KiB
GLSL
67 lines
1.9 KiB
GLSL
#version 100
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precision mediump float;
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uniform float u_time;
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uniform vec2 u_resolution;
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uniform vec2 u_mouse;
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uniform sampler2D u_backbuffer;
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// Fluid Parameters
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#define DT 0.15
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#define VISCOSITY 0.99
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#define FADE 0.995
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// Pseudo-random
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float rand(vec2 co){
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return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
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}
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void main() {
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vec2 pixel = 1.0 / u_resolution;
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vec2 uv = gl_FragCoord.xy / u_resolution;
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// 1. Read current state (Vel, Density)
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if (u_time < 0.5 || u_resolution.x < 1.0) {
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gl_FragColor = vec4(0.5, 0.5, 0.0, 1.0);
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return;
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}
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vec4 state = texture2D(u_backbuffer, uv);
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vec2 vel = state.xy; // velocity range [-1, 1]? we store as [0,1]. Need remap.
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// Actually simpler to store raw flow in 0..1 range whre 0.5 is 0 velocity.
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// Let's assume 0.5 is 0.
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vec2 v = (vel - 0.5) * 2.0;
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float density = state.z;
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// 2. Advection (move state by velocity)
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// We look *back* along velocity to find where the current content came from.
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vec2 coord = uv - v * pixel * 5.0; // Scale velocity effect
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vec4 advected = texture2D(u_backbuffer, coord);
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vec2 new_v = (advected.xy - 0.5) * 2.0;
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float new_d = advected.z;
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// 3. Mouse Interaction (Splat)
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float d = distance(gl_FragCoord.xy, u_mouse);
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if (d < 30.0 && u_mouse.x > 0.0) {
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// Add density
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new_d += 0.5;
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// Add velocity (push away from mouse or just random?)
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// Ideally we need mouse delta (velocity). u_mouse is just pos.
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// We can just add a radial force or flow?
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// Let's just add some noise/movement
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new_v += vec2(rand(uv + u_time) - 0.5, rand(uv + u_time + 1.0) - 0.5) * 1.0;
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}
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// 4. Decay (Viscosity/Dissipation)
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new_v *= VISCOSITY;
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new_d *= FADE;
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// Remap velocity back to 0..1
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vel = new_v * 0.5 + 0.5;
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gl_FragColor = vec4(vel, new_d, 1.0);
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}
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