1/* 2 * Copyright (C) 2024 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17/** 18 * Draw a single splash. 19 * @param cellUv Range of [-0.5, 0.5]: left bottom (-0.5, -0.5), right top (0.5, 0.5). 20 * @param cellTime Normalized cellTime range of [0, 1]. 21 */ 22float drawSplash(vec2 cellUv, float cellTime) { 23 /** 0. Adjust UV and time. */ 24 cellUv *= 0.5; 25 // Moves drop a little bit down on the its grid cell. 26 cellUv.y += 0.15; 27 float t = 0.408 + cellTime * 4.; 28 29 /** 1. Start of drawing a splash */ 30 31 // Draw one side of a splash (a crescent) using two circles, by overlapping them with a slight 32 // offset. Then we reflect the splash to get the full splash. 33 34 // Reflect the splash. 35 vec2 uvAbs = abs(cellUv); 36 37 // Center of the splash (of the right splash) 38 vec2 center = vec2(0.22, -0.01); 39 float splashMaskCircle1 = sdfCircle(uvAbs - center, 0.164); 40 float splashMaskCircle2 = sdfCircle(uvAbs - vec2(0.04, 0.) - center, 0.164); 41 42 splashMaskCircle1 = smoothstep(0.052, 0.12, splashMaskCircle1); 43 splashMaskCircle2 = smoothstep(0.1, 0.152, splashMaskCircle2); 44 45 // Here, we have a full splash that covers the entire cell 46 float splash = splashMaskCircle1 - splashMaskCircle2; 47 48 // Mask the splash so that it doesn't cover the entire cell. 49 float circleMask = sdfCircle(cellUv - vec2(0., 0.15), -0.004); 50 float splashColor = splash * smoothstep(0.152, 0.1, circleMask); 51 52 // Another mask for the splash to reveal it vertically. 53 float maskThickHalf = 0.052; 54 float maskFade = 0.05; 55 vec2 maskMiddle = vec2(-0.1, -0.5); 56 maskMiddle.y *= sin(mod(t, 4.4)); 57 58 float mask = 59 smoothstep(maskMiddle.y - maskThickHalf - maskFade, 60 maskMiddle.y - maskThickHalf, 61 cellUv.y) - 62 smoothstep(maskMiddle.y + maskThickHalf, 63 maskMiddle.y + maskThickHalf + maskFade, 64 cellUv.y); 65 splashColor *= mask; 66 /** End of drawing a splash */ 67 68 /** 2. Start of drawing a vertical line of the splash */ 69 70 // Draw the vertical line. 71 float verticalLine = 0.035; 72 float lineCenter = 0.192; 73 float lineColor = 0.4 * 74 (smoothstep(-verticalLine, 0., cellUv.x) - smoothstep(0., verticalLine, cellUv.x)) * 75 smoothstep(0.008, -0.156, sdfCircle(cellUv - vec2(0., lineCenter), 0.164)); 76 77 // Mask the vertical line to reveal it vertically. 78 float lineMaskThickHalf = 0.124; 79 float lineMaskFade = 0.170; 80 vec2 lineMaskMiddle = vec2(-0.01, 2.71); 81 lineMaskMiddle.y *= sin(mod(t, 4.4) - 0.168); 82 float lineMask = 83 smoothstep(lineMaskMiddle.y - lineMaskThickHalf - lineMaskFade, 84 lineMaskMiddle.y - lineMaskThickHalf, 85 cellUv.y) - 86 smoothstep(lineMaskMiddle.y + lineMaskThickHalf, 87 lineMaskMiddle.y + lineMaskThickHalf + lineMaskFade, 88 cellUv.y); 89 float line = lineColor * lineMask; 90 91 /** End of drawing the vertical line of the splash */ 92 93 /** 3. Composite the splash and the line. */ 94 return splashColor * (1. - line) + line; 95} 96