/* This file is part of Magnum. Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023 Vladimír Vondruš Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ #ifndef NEW_GLSL #define in varying #define value gl_FragColor.x #define texture texture2D #endif #ifndef RUNTIME_CONST #define const #endif #if (defined(GL_ES) && __VERSION__ >= 300) || (!defined(GL_ES) && __VERSION__ >= 150) #define TEXELFETCH_USABLE #endif #ifdef EXPLICIT_BINDING layout(binding = 7) #endif uniform lowp sampler2D textureData; #ifndef TEXELFETCH_USABLE #ifdef EXPLICIT_UNIFORM_LOCATION layout(location = 0) #endif uniform mediump vec2 imageSizeInverted; #endif in mediump vec2 inputTextureCoordinates; #ifdef NEW_GLSL out lowp float value; #endif #ifdef TEXELFETCH_USABLE bool hasValue(const mediump ivec2 position, const mediump ivec2 offset) { return texelFetch(textureData, position + offset, 0).r > 0.5; } #else bool hasValue(const mediump vec2 position, const mediump ivec2 offset) { return texture(textureData, position + vec2(offset)*imageSizeInverted).r > 0.5; } #endif mediump float findMinDistanceSquared(const mediump #ifdef TEXELFETCH_USABLE ivec2 #else vec2 #endif position, const bool isInside) { /* Initialize minimal distance to a value just outside the radius. As the output coordinate is shifted by half a pixel from the input (see the diagram in main() below), the X/Y distances are always a whole pixel minus 0.5. Thus the max distance found in the below loop can be at most `RADIUS - 0.5`, and the next nearest distance is thus `RADIUS + 0.5`. */ mediump float minDistanceSquared = (float(RADIUS)+0.5)*(float(RADIUS)+0.5); /* Go in cocentric squares around the point */ for(int i = 2; i <= RADIUS; ++i) { /* Actual distance from the center for this iteration is half a pixel less (see the diagram in main() below) */ const mediump float iF = float(i) - 0.5; /* Check for points further away from the initial 2x2 square, except for corners. Every iteration checks all eight rotations/reflections at the same distance. If the distance in given iteration is not less than what's found already, we don't even check the texture -- but can't return, since next iteration can still have closer values. i = 2 i = 3 9108 10 a f 2 7 2 7 3p 6 3 p 6 45 b e c45d Once we find something, it's the closest value possible in this cycle, so we stop the cycle. But next iterations can still have values that are closer, so can't return. Note that the integer `position` isn't at the center, which means the offsets aren't symmetric. */ for(int j = 1; j < RADIUS; ++j) { /* Don't go further than current radius - 1 (i.e., excluding the corner). The loop needs to be compile-time bound otherwise some drivers crash on it, so we're breaking inside instead of having this directly in the loop condition. */ if(j >= i) break; /* Again, actual distance from the center is half a pixel less (see the diagram in main() below) */ const mediump float jF = float(j) - 0.5; const mediump float sideDistanceSquared = iF*iF + jF*jF; if(sideDistanceSquared >= minDistanceSquared) break; if(hasValue(position, ivec2( j, i)) != isInside || /* 0, 8 */ hasValue(position, ivec2(1-j, i)) != isInside || /* 1, 9 */ hasValue(position, ivec2(1-i, j)) != isInside || /* 2, a */ hasValue(position, ivec2(1-i, 1-j)) != isInside || /* 3, b */ hasValue(position, ivec2(1-j, 1-i)) != isInside || /* 4, c */ hasValue(position, ivec2( j, 1-i)) != isInside || /* 5, d */ hasValue(position, ivec2( i, 1-j)) != isInside || /* 6, e */ hasValue(position, ivec2( i, j)) != isInside) { /* 7, f */ minDistanceSquared = sideDistanceSquared; break; } } /* Then check for the corners, which is just four cases. Again the integer `position` isn't at the center, which means the offsets aren't symmetric. i = 2 i = 3 1 0 1 0 p p 2 3 2 3 If we find something, it's most probably not the nearest distance, since the following iterations can be much closer. */ const mediump float cornerDistanceSquared = 2.0*iF*iF; if(cornerDistanceSquared >= minDistanceSquared) continue; if(hasValue(position, ivec2( i, i)) != isInside || hasValue(position, ivec2(1-i, i)) != isInside || hasValue(position, ivec2(1-i, 1-i)) != isInside || hasValue(position, ivec2( i, 1-i)) != isInside) { minDistanceSquared = cornerDistanceSquared; } } return minDistanceSquared; } void main() { /* The -0.5 is to make the position aligned with the center of the input pixel, and in the integer case to make the conversion not round up */ #ifdef TEXELFETCH_USABLE const mediump ivec2 position = ivec2(inputTextureCoordinates - vec2(0.5)); #else const mediump vec2 position = inputTextureCoordinates - vec2(0.5)*imageSizeInverted; #endif /* +=======+===== H | | | H | | Assuming the ratio of input and output sizes is a H-+-+-+-H-+-+ multiple of 2 (in this diagram it's scaled 4x), the H |k|l| H | center of the output pixel `o` is always between four H-+-o-+-H-+ input pixels `i`, `j`, `k`, `l`.Then, depending on H |i|j| H which of the four input pixels have a value > 0.5, the H-+-+-+-H- following six cases can happen. Other combinations are H | | | just variants of these. +===== - In case A and F, the pixel is either inside or outside and we have to look further around to know the distance to the edge. - In case B and C, the pixel is exactly on the edge, i.e. distance is 0, and we don't need to look further. - In case D and E, the pixel is at a distance of 0.5 or (0.5, 0.5) from the edge, and we don't need to look further. A B C D | E F k---l k---l k l k l -k l k l | | | / / | | o | | o o | o o o | | |/ / | i---j i j i j i j i j i j The main complication is distinguishing cases C and D, in all other cases it's simply a matter of counting the number of pixels that have a value of > 0.5. Note that the integer `position` isn't at `o` (which is between pixels) but aliases `i`. Which means the offsets aren't symmetric. */ const bool i = hasValue(position, ivec2(0, 0)); const bool j = hasValue(position, ivec2(1, 0)); const bool k = hasValue(position, ivec2(0, 1)); const bool l = hasValue(position, ivec2(1, 1)); mediump float minDistance; bool isInside; const int sum = int(i) + int(j) + int(k) + int(l); /* Case B */ if(sum == 3) { isInside = false; minDistance = 0.0; /* Case C and D */ } else if(sum == 2) { isInside = false; if((i && l) || (j && k)) minDistance = 0.0; else minDistance = 0.5; /* Case E */ } else if(sum == 1) { isInside = false; /* sqrt(0.5*0.5 + 0.5*0.5) */ minDistance = 0.7071067811865475; /* Case A and F */ } else { isInside = sum == 4; minDistance = sqrt(float(findMinDistanceSquared(position, isInside))); } /* Final signed distance, normalized from [-radius + 0.5, radius + 0.5] to [0, 1] */ const highp float halfSign = isInside ? 0.5 : -0.5; value = halfSign*minDistance/(float(RADIUS) + 0.5) + 0.5; }