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| 1 | +//Taken from https://github.com/sahaj-b/ghostty-cursor-shaders |
| 2 | +// -- CONFIGURATION -- |
| 3 | +vec4 TRAIL_COLOR = iCurrentCursorColor; // can change to eg: vec4(0.2, 0.6, 1.0, 0.5); |
| 4 | +const float DURATION = 0.08; // in seconds |
| 5 | +const float MAX_TRAIL_LENGTH = 0.15; |
| 6 | +const float THRESHOLD_MIN_DISTANCE = 1.0; // min distance to show trail (units of cursor width) |
| 7 | +const float BLUR = 2.0; // blur size in pixels (for antialiasing) |
| 8 | + |
| 9 | +// --- CONSTANTS for easing functions --- |
| 10 | +const float PI = 3.14159265359; |
| 11 | +const float C1_BACK = 1.70158; |
| 12 | +const float C2_BACK = C1_BACK * 1.525; |
| 13 | +const float C3_BACK = C1_BACK + 1.0; |
| 14 | +const float C4_ELASTIC = (2.0 * PI) / 3.0; |
| 15 | +const float C5_ELASTIC = (2.0 * PI) / 4.5; |
| 16 | +const float SPRING_STIFFNESS = 9.0; |
| 17 | +const float SPRING_DAMPING = 0.9; |
| 18 | + |
| 19 | +// --- EASING FUNCTIONS --- |
| 20 | + |
| 21 | +// // Linear |
| 22 | +// float ease(float x) { |
| 23 | +// return x; |
| 24 | +// } |
| 25 | + |
| 26 | +// // EaseOutQuad |
| 27 | +// float ease(float x) { |
| 28 | +// return 1.0 - (1.0 - x) * (1.0 - x); |
| 29 | +// } |
| 30 | + |
| 31 | +// // EaseOutCubic |
| 32 | +// float ease(float x) { |
| 33 | +// return 1.0 - pow(1.0 - x, 3.0); |
| 34 | +// } |
| 35 | + |
| 36 | + |
| 37 | +// // EaseOutQuart |
| 38 | +// float ease(float x) { |
| 39 | +// return 1.0 - pow(1.0 - x, 4.0); |
| 40 | +// } |
| 41 | + |
| 42 | +// // EaseOutQuint |
| 43 | +// float ease(float x) { |
| 44 | +// return 1.0 - pow(1.0 - x, 5.0); |
| 45 | +// } |
| 46 | + |
| 47 | +// // EaseOutSine |
| 48 | +// float ease(float x) { |
| 49 | +// return sin((x * PI) / 2.0); |
| 50 | +// } |
| 51 | + |
| 52 | +// // EaseOutExpo |
| 53 | +// float ease(float x) { |
| 54 | +// return x == 1.0 ? 1.0 : 1.0 - pow(2.0, -10.0 * x); |
| 55 | +// } |
| 56 | + |
| 57 | +// EaseOutCirc |
| 58 | +float ease(float x) { |
| 59 | + return sqrt(1.0 - pow(x - 1.0, 2.0)); |
| 60 | +} |
| 61 | + |
| 62 | +// // EaseOutBack |
| 63 | +// float ease(float x) { |
| 64 | +// return 1.0 + C3_BACK * pow(x - 1.0, 3.0) + C1_BACK * pow(x - 1.0, 2.0); |
| 65 | +// } |
| 66 | + |
| 67 | +// // EaseOutElastic |
| 68 | +// float ease(float x) { |
| 69 | +// return x == 0.0 ? 0.0 |
| 70 | +// : x == 1.0 ? 1.0 |
| 71 | +// : pow(2.0, -10.0 * x) * sin((x * 10.0 - 0.75) * C4_ELASTIC) + 1.0; |
| 72 | +// } |
| 73 | + |
| 74 | +// Parametric Spring |
| 75 | +// float ease(float x) { |
| 76 | +// x = clamp(x, 0.0, 1.0); |
| 77 | +// float decay = exp(-SPRING_DAMPING * SPRING_STIFFNESS * x); |
| 78 | +// float freq = sqrt(SPRING_STIFFNESS * (1.0 - SPRING_DAMPING * SPRING_DAMPING)); |
| 79 | +// float osc = cos(freq * 6.283185 * x) + (SPRING_DAMPING * sqrt(SPRING_STIFFNESS) / freq) * sin(freq * 6.283185 * x); |
| 80 | +// return 1.0 - decay * osc; |
| 81 | +// } |
| 82 | + |
| 83 | +float getSdfRectangle(in vec2 p, in vec2 xy, in vec2 b) |
| 84 | +{ |
| 85 | + vec2 d = abs(p - xy) - b; |
| 86 | + return length(max(d, 0.0)) + min(max(d.x, d.y), 0.0); |
| 87 | +} |
| 88 | + |
| 89 | +// Based on Inigo Quilez's 2D distance functions article: https://iquilezles.org/articles/distfunctions2d/ |
| 90 | +// Potencially optimized by eliminating conditionals and loops to enhance performance and reduce branching |
| 91 | + |
| 92 | +float seg(in vec2 p, in vec2 a, in vec2 b, inout float s, float d) { |
| 93 | + vec2 e = b - a; |
| 94 | + vec2 w = p - a; |
| 95 | + vec2 proj = a + e * clamp(dot(w, e) / dot(e, e), 0.0, 1.0); |
| 96 | + float segd = dot(p - proj, p - proj); |
| 97 | + d = min(d, segd); |
| 98 | + |
| 99 | + float c0 = step(0.0, p.y - a.y); |
| 100 | + float c1 = 1.0 - step(0.0, p.y - b.y); |
| 101 | + float c2 = 1.0 - step(0.0, e.x * w.y - e.y * w.x); |
| 102 | + float allCond = c0 * c1 * c2; |
| 103 | + float noneCond = (1.0 - c0) * (1.0 - c1) * (1.0 - c2); |
| 104 | + float flip = mix(1.0, -1.0, step(0.5, allCond + noneCond)); |
| 105 | + s *= flip; |
| 106 | + return d; |
| 107 | +} |
| 108 | + |
| 109 | +float getSdfParallelogram(in vec2 p, in vec2 v0, in vec2 v1, in vec2 v2, in vec2 v3) { |
| 110 | + float s = 1.0; |
| 111 | + float d = dot(p - v0, p - v0); |
| 112 | + |
| 113 | + d = seg(p, v0, v3, s, d); |
| 114 | + d = seg(p, v1, v0, s, d); |
| 115 | + d = seg(p, v2, v1, s, d); |
| 116 | + d = seg(p, v3, v2, s, d); |
| 117 | + |
| 118 | + return s * sqrt(d); |
| 119 | +} |
| 120 | + |
| 121 | +vec2 normalize(vec2 value, float isPosition) { |
| 122 | + return (value * 2.0 - (iResolution.xy * isPosition)) / iResolution.y; |
| 123 | +} |
| 124 | + |
| 125 | +float antialising(float distance) { |
| 126 | + return 1. - smoothstep(0., normalize(vec2(BLUR, BLUR), 0.).x, distance); |
| 127 | +} |
| 128 | + |
| 129 | +float determineIfTopRightIsLeading(vec2 a, vec2 b) { |
| 130 | + float condition1 = step(b.x, a.x) * step(a.y, b.y); // a.x < b.x && a.y > b.y |
| 131 | + float condition2 = step(a.x, b.x) * step(b.y, a.y); // a.x > b.x && a.y < b.y |
| 132 | + |
| 133 | + // if neither condition is met, return 1 (else case) |
| 134 | + return 1.0 - max(condition1, condition2); |
| 135 | +} |
| 136 | + |
| 137 | +vec2 getRectangleCenter(vec4 rectangle) { |
| 138 | + return vec2(rectangle.x + (rectangle.z / 2.), rectangle.y - (rectangle.w / 2.)); |
| 139 | +} |
| 140 | + |
| 141 | + |
| 142 | +void mainImage(out vec4 fragColor, in vec2 fragCoord){ |
| 143 | + #if !defined(WEB) |
| 144 | + fragColor = texture(iChannel0, fragCoord.xy / iResolution.xy); |
| 145 | + #endif |
| 146 | + |
| 147 | + // normalization & setup(-1, 1 coords) |
| 148 | + vec2 vu = normalize(fragCoord, 1.); |
| 149 | + vec2 offsetFactor = vec2(-.5, 0.5); |
| 150 | + |
| 151 | + vec4 currentCursor = vec4(normalize(iCurrentCursor.xy, 1.), normalize(iCurrentCursor.zw, 0.)); |
| 152 | + vec4 previousCursor = vec4(normalize(iPreviousCursor.xy, 1.), normalize(iPreviousCursor.zw, 0.)); |
| 153 | + |
| 154 | + vec2 centerCC = currentCursor.xy - (currentCursor.zw * offsetFactor); |
| 155 | + vec2 centerCP = previousCursor.xy - (previousCursor.zw * offsetFactor); |
| 156 | + |
| 157 | + vec2 delta = centerCP - centerCC; |
| 158 | + float lineLength = length(delta); |
| 159 | + |
| 160 | + float sdfCurrentCursor = getSdfRectangle(vu, centerCC, currentCursor.zw * 0.5); |
| 161 | + |
| 162 | + vec4 newColor = vec4(fragColor); |
| 163 | + |
| 164 | + float minDist = currentCursor.w * THRESHOLD_MIN_DISTANCE; |
| 165 | + float progress = clamp((iTime - iTimeCursorChange) / DURATION, 0.0, 1.0); |
| 166 | + if (lineLength > minDist) { |
| 167 | + // ANIMATION logic |
| 168 | + |
| 169 | + float head_eased = 0.0; |
| 170 | + float tail_eased = 0.0; |
| 171 | + |
| 172 | + float tail_delay_factor = MAX_TRAIL_LENGTH / lineLength; |
| 173 | + |
| 174 | + float isLongMove = step(MAX_TRAIL_LENGTH, lineLength); |
| 175 | + |
| 176 | + float head_eased_short = ease(progress); |
| 177 | + float tail_eased_short = ease(smoothstep(tail_delay_factor, 1.0, progress)); |
| 178 | + float head_eased_long = 1.0; |
| 179 | + float tail_eased_long = ease(progress); |
| 180 | + |
| 181 | + head_eased = mix(head_eased_long, head_eased_short, isLongMove); |
| 182 | + tail_eased = mix(tail_eased_long, tail_eased_short, isLongMove); |
| 183 | + |
| 184 | + // detect straight moves |
| 185 | + vec2 delta_abs = abs(centerCC - centerCP); |
| 186 | + float threshold = 0.001; |
| 187 | + float isHorizontal = step(delta_abs.y, threshold); |
| 188 | + float isVertical = step(delta_abs.x, threshold); |
| 189 | + float isStraightMove = max(isHorizontal, isVertical); |
| 190 | + |
| 191 | + // -- Making the parallelogram sdf (diagonal move) -- |
| 192 | + |
| 193 | + // animate the TOP-LEFT corners |
| 194 | + vec2 head_pos_tl = mix(previousCursor.xy, currentCursor.xy, head_eased); |
| 195 | + vec2 tail_pos_tl = mix(previousCursor.xy, currentCursor.xy, tail_eased); |
| 196 | + |
| 197 | + float isTopRightLeading = determineIfTopRightIsLeading(currentCursor.xy, previousCursor.xy); |
| 198 | + float isBottomLeftLeading = 1.0 - isTopRightLeading; |
| 199 | + |
| 200 | + // v0, v1 : "front" of the trail (head) |
| 201 | + vec2 v0 = vec2(head_pos_tl.x + currentCursor.z * isTopRightLeading, head_pos_tl.y - currentCursor.w); |
| 202 | + vec2 v1 = vec2(head_pos_tl.x + currentCursor.z * isBottomLeftLeading, head_pos_tl.y); |
| 203 | + |
| 204 | + // v2, v3: "back" of the trail (tail) |
| 205 | + vec2 v2 = vec2(tail_pos_tl.x + currentCursor.z * isBottomLeftLeading, tail_pos_tl.y); |
| 206 | + vec2 v3 = vec2(tail_pos_tl.x + currentCursor.z * isTopRightLeading, tail_pos_tl.y - previousCursor.w); |
| 207 | + |
| 208 | + float sdfTrail_diag = getSdfParallelogram(vu, v0, v1, v2, v3); |
| 209 | + |
| 210 | + // -- Making the rectangle sdf (straight move) -- |
| 211 | + |
| 212 | + vec2 head_center = mix(centerCP, centerCC, head_eased); |
| 213 | + vec2 tail_center = mix(centerCP, centerCC, tail_eased); |
| 214 | + |
| 215 | + vec2 min_center = min(head_center, tail_center); |
| 216 | + vec2 max_center = max(head_center, tail_center); |
| 217 | + |
| 218 | + vec2 box_size = (max_center - min_center) + currentCursor.zw; |
| 219 | + vec2 box_center = (min_center + max_center) * 0.5; |
| 220 | + |
| 221 | + float sdfTrail_rect = getSdfRectangle(vu, box_center, box_size * 0.5); |
| 222 | + |
| 223 | + // -- FINAL SELECTING AND DRAWING -- |
| 224 | + float sdfTrail = mix(sdfTrail_diag, sdfTrail_rect, isStraightMove); |
| 225 | + |
| 226 | + vec4 trail = TRAIL_COLOR; |
| 227 | + float trailAlpha = antialising(sdfTrail); |
| 228 | + newColor = mix(newColor, trail, trailAlpha); |
| 229 | + |
| 230 | + // punch hole |
| 231 | + newColor = mix(newColor, fragColor, step(sdfCurrentCursor, 0.)); |
| 232 | + } |
| 233 | + |
| 234 | + fragColor = newColor; |
| 235 | +} |
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