@kitware/vtk.js/Rendering/OpenGL/SurfaceLIC/glsl/vtkLineIntegralConvolution2D_LICI.glsl.js

Visualization Toolkit for the Web

var vtkLineIntegralConvolution2D_LICI = "//VTK::System::Dec\n\n//=========================================================================\n//\n//  Program:   Visualization Toolkit\n//  Module:    vtkLineIntegralConvolution2D_fs1.glsl\n//\n//  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen\n//  All rights reserved.\n//  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.\n//\n//     This software is distributed WITHOUT ANY WARRANTY; without even\n//     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR\n//     PURPOSE.  See the above copyright notice for more information.\n//\n//=========================================================================\n\n// the output of this shader\nlayout(location = 0) out vec4 LICOutput;\nlayout(location = 1) out vec4 SeedOutput;\n\nuniform sampler2D  texVectors;\nuniform sampler2D  texNoise;\nuniform sampler2D  texLIC;\nuniform sampler2D  texSeedPts;\n\nuniform int   uPassNo;          // in pass 1 hpf of pass 0 is convolved.\nuniform float uStepSize;        // step size in parametric space\n\nuniform vec2  uNoiseBoundsPt1;  // tc of upper right pt of noise texture\n\nin vec2 tcoordVC;\n\n//VTK::LICVectorLookup::Impl\n\n// We need to do this manually since CLAMP_TO_BORDER and and borderColor\n// are very poorly supported in webgl\nvec2 clampToBorder(vec2 uv){\n  if(uv.x < 0.0 || uv.x > 1.0 || uv.y < 0.0 || uv.y > 1.0)\n  {\n    return vec2(0.0, 0.0);\n  }\n  return getVector(uv);\n}\n\n// convert from vector coordinate space to noise coordinate space.\n// the noise texture is tiled across the whole domain\nvec2 VectorTCToNoiseTC(vec2 vectc)\n{\n  return vectc/uNoiseBoundsPt1;\n}\n\n// get the texture coordidnate to lookup noise value.\n// in pass 1 repeatedly tile the noise texture across\n// the computational domain.\nvec2 getNoiseTC(vec2 tc)\n{\n  if (uPassNo == 0)\n    {\n    return VectorTCToNoiseTC(tc);\n    }\n  else\n    {\n    return tc;\n    }\n}\n\n// look up noise value at the given location. The location\n// is supplied in vector texture coordinates, hence the need\n// to convert to either noise or lic texture coordinates in\n// pass 1 and 2 respectively.\nfloat getNoise(vec2 vectc)\n{\n  return texture2D(texNoise, getNoiseTC(vectc)).r;\n}\n\n// fourth-order Runge-Kutta streamline integration\n// no bounds checks are made, therefore it's essential\n// to have the entire texture initialized to 0\n// and set clamp to border and have border color 0\n// an integer is set if the step was taken, keeping\n// an accurate step count is necessary to prevent\n// boundary artifacts. Don't count the step if\n// all vector lookups are identically 0. This is\n// a proxy for \"stepped outside valid domain\"\nvec2 rk4(vec2 pt0, float dt, out bool count)\n{\n  count=true;\n  float dtHalf = dt * 0.5;\n  vec2 pt1;\n\n  vec2 v0 = clampToBorder(pt0);\n  pt1 = pt0 + v0 * dtHalf;\n\n  vec2 v1 = clampToBorder(pt1);\n  pt1 = pt0 + v1 * dtHalf;\n\n  vec2 v2 = clampToBorder(pt1);\n  pt1 = pt0 + v2 * dt;\n\n  vec2 v3 = clampToBorder(pt1);\n  vec2 vSum = v0 + v1 + v1 + v2 + v2 + v3;\n\n  if (vSum == vec2(0.0, 0.0))\n    {\n      count = false;\n    }\n\n  pt1 = pt0 + (vSum) * (dt * (1.0/6.0));\n\n return pt1;\n}\n\nvoid main(void)\n{\n  vec2 lictc = tcoordVC.st;\n  vec4 lic = texture2D(texLIC, lictc);\n  vec2 pt0 = texture2D(texSeedPts, lictc).st;\n\n  bool count;\n  vec2 pt1 = rk4(pt0, uStepSize, count);\n\n  if (count)\n    {\n    // accumulate lic step\n    // (lic, mask, 0, step count)\n    float noise = getNoise(pt1);\n    LICOutput = vec4(lic.r + noise, lic.g, 0.0, lic.a + 1.0);\n    SeedOutput = vec4(pt1, 0.0, 1.0);\n    }\n  else\n    {\n    // keep existing values\n    LICOutput = lic;\n    SeedOutput = vec4(pt0, 0.0, 1.0);\n    }\n}\n";

export { vtkLineIntegralConvolution2D_LICI as v };