Mercurial > hg > orthanc-stone
diff Framework/Scene2D/Internals/OpenGLLinesProgram.cpp @ 592:bbe29efd3d1c
OpenGLLinesProgram
author | Sebastien Jodogne <s.jodogne@gmail.com> |
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date | Fri, 26 Apr 2019 12:55:43 +0200 |
parents | |
children | e3f21a265be5 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Framework/Scene2D/Internals/OpenGLLinesProgram.cpp Fri Apr 26 12:55:43 2019 +0200 @@ -0,0 +1,459 @@ +/** + * Stone of Orthanc + * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics + * Department, University Hospital of Liege, Belgium + * Copyright (C) 2017-2019 Osimis S.A., Belgium + * + * This program is free software: you can redistribute it and/or + * modify it under the terms of the GNU Affero General Public License + * as published by the Free Software Foundation, either version 3 of + * the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + **/ + + +#include "OpenGLLinesProgram.h" + +#include <Core/OrthancException.h> + + +static const unsigned int COMPONENTS_POSITION = 3; +static const unsigned int COMPONENTS_MITER = 2; + + +static const char* VERTEX_SHADER = + "attribute vec2 a_miter_direction; \n" + "attribute vec4 a_position; \n" + "uniform float u_thickness; \n" + "uniform mat4 u_matrix; \n" + "varying float v_distance; \n" + "void main() \n" + "{ \n" + " v_distance = a_position.z; \n" + " gl_Position = u_matrix * vec4(a_position.xy + a_position.z * a_miter_direction * u_thickness, 0, 1); \n" + "}"; + + +static const char* FRAGMENT_SHADER = + "uniform bool u_antialiasing; \n" + "uniform float u_antialiasing_start; \n" + "uniform vec3 u_color; \n" + "varying float v_distance; \n" // Distance of the point to the segment + "void main() \n" + "{ \n" + " float d = abs(v_distance); \n" + " if (!u_antialiasing || \n" + " d <= u_antialiasing_start) \n" + " gl_FragColor = vec4(u_color, 1); \n" + " else if (d >= 1.0) \n" + " gl_FragColor = vec4(0, 0, 0, 0); \n" + " else \n" + " { \n" + " float alpha = 1.0 - smoothstep(u_antialiasing_start, 1.0, d); \n" + " gl_FragColor = vec4(u_color * alpha, alpha); \n" + " } \n" + "}"; + + +namespace OrthancStone +{ + namespace Internals + { + class OpenGLLinesProgram::Data::Segment + { + private: + bool isEmpty_; + double x1_; + double y1_; + double x2_; + double y2_; + double miterX1_; + double miterY1_; + double miterX2_; + double miterY2_; + + Vector lineAbove_; // In homogeneous coordinates (size = 3) + Vector lineBelow_; + + public: + Segment(const PolylineSceneLayer::Chain& chain, + size_t index1, + size_t index2) : + isEmpty_(false) + { + if (index1 >= chain.size() || + index2 >= chain.size()) + { + throw Orthanc::OrthancException(Orthanc::ErrorCode_ParameterOutOfRange); + } + else + { + const ScenePoint2D& p = chain[index1]; + const ScenePoint2D& q = chain[index2]; + + x1_ = p.GetX(); + y1_ = p.GetY(); + x2_ = q.GetX(); + y2_ = q.GetY(); + + const double dx = x2_ - x1_; + const double dy = y2_ - y1_; + const double norm = sqrt(dx * dx + dy * dy); + + if (LinearAlgebra::IsCloseToZero(norm)) + { + isEmpty_ = true; + } + else + { + isEmpty_ = false; + const double normalX = -dy / norm; + const double normalY = dx / norm; + + miterX1_ = normalX; + miterY1_ = normalY; + miterX2_ = normalX; + miterY2_ = normalY; + + Vector a = LinearAlgebra::CreateVector(x1_ + normalX, y1_ + normalY, 1); + Vector b = LinearAlgebra::CreateVector(x2_ + normalX, y2_ + normalY, 1); + LinearAlgebra::CrossProduct(lineAbove_, a, b); + + a = LinearAlgebra::CreateVector(x1_ - normalX, y1_ - normalY, 1); + b = LinearAlgebra::CreateVector(x2_ - normalX, y2_ - normalY, 1); + LinearAlgebra::CrossProduct(lineBelow_, a, b); + } + } + } + + bool IsEmpty() const + { + return isEmpty_; + } + + static double ComputeSignedArea(double x1, + double y1, + double x2, + double y2, + double x3, + double y3) + { + // This computes the signed area of a 2D triangle. This + // formula is e.g. used in the sorting algorithm of Graham's + // scan to compute the convex hull. + // https://en.wikipedia.org/wiki/Graham_scan + return (x2 - x1) * (y3 - y1) - (y2 - y1) * (x3 - x1); + } + + static void CreateMiter(Segment& left, + Segment& right) + { + if (!left.IsEmpty() && + !right.IsEmpty()) + { + Vector above, below; + LinearAlgebra::CrossProduct(above, left.lineAbove_, right.lineAbove_); + LinearAlgebra::CrossProduct(below, left.lineBelow_, right.lineBelow_); + + if (!LinearAlgebra::IsCloseToZero(above[2]) && + !LinearAlgebra::IsCloseToZero(below[2])) + { + // Back to inhomogeneous 2D coordinates + above /= above[2]; + below /= below[2]; + + // Check whether "above" and "below" intersection points + // are on the half-plane defined by the endpoints of the + // two segments. This is an indicator of whether the angle + // is too acute. + double s1 = ComputeSignedArea(left.x1_, left.y1_, + above[0], above[1], + right.x2_, right.y2_); + double s2 = ComputeSignedArea(left.x1_, left.y1_, + below[0], below[1], + right.x2_, right.y2_); + + // The two signed areas must have the same sign + if (s1 * s2 >= 0) + { + left.miterX2_ = above[0] - left.x2_; + left.miterY2_ = above[1] - left.y2_; + + right.miterX1_ = left.miterX2_; + right.miterY1_ = left.miterY2_; + } + } + } + } + + void AddTriangles(std::vector<float>& coords, + std::vector<float>& miterDirections) + { + if (isEmpty_) + { + throw Orthanc::OrthancException(Orthanc::ErrorCode_BadSequenceOfCalls); + } + + // First triangle + coords.push_back(x1_); + coords.push_back(y1_); + coords.push_back(1); + coords.push_back(x2_); + coords.push_back(y2_); + coords.push_back(-1); + coords.push_back(x2_); + coords.push_back(y2_); + coords.push_back(1); + + miterDirections.push_back(miterX1_); + miterDirections.push_back(miterY1_); + miterDirections.push_back(miterX2_); + miterDirections.push_back(miterY2_); + miterDirections.push_back(miterX2_); + miterDirections.push_back(miterY2_); + + // Second triangle + coords.push_back(x1_); + coords.push_back(y1_); + coords.push_back(1); + coords.push_back(x1_); + coords.push_back(y1_); + coords.push_back(-1); + coords.push_back(x2_); + coords.push_back(y2_); + coords.push_back(-1); + + miterDirections.push_back(miterX1_); + miterDirections.push_back(miterY1_); + miterDirections.push_back(miterX1_); + miterDirections.push_back(miterY1_); + miterDirections.push_back(miterX2_); + miterDirections.push_back(miterY2_); + } + }; + + + OpenGLLinesProgram::Data::Data(OpenGL::IOpenGLContext& context, + const PolylineSceneLayer& layer) : + context_(context), + verticesCount_(0), + thickness_(layer.GetThickness()), + red_(layer.GetRedAsFloat()), + green_(layer.GetGreenAsFloat()), + blue_(layer.GetBlueAsFloat()) + { + // High-level reference: + // https://mattdesl.svbtle.com/drawing-lines-is-hard + // https://forum.libcinder.org/topic/smooth-thick-lines-using-geometry-shader + + size_t countVertices = 0; + for (size_t i = 0; i < layer.GetChainsCount(); i++) + { + size_t countSegments = layer.GetChain(i).size() - 1; + + if (layer.IsClosedChain(i)) + { + countSegments++; + } + + // Each segment is made of 2 triangles. One triangle is + // defined by 3 points in 2D => 6 vertices per segment. + countVertices += countSegments * 2 * 3; + } + + std::vector<float> coords, miterDirections; + coords.reserve(countVertices * COMPONENTS_POSITION); + miterDirections.reserve(countVertices * COMPONENTS_MITER); + + for (size_t i = 0; i < layer.GetChainsCount(); i++) + { + const PolylineSceneLayer::Chain& chain = layer.GetChain(i); + + if (chain.size() > 1) + { + std::vector<Segment> segments; + for (size_t j = 1; j < chain.size(); j++) + { + segments.push_back(Segment(chain, j - 1, j)); + } + + if (layer.IsClosedChain(i)) + { + segments.push_back(Segment(chain, chain.size() - 1, 0)); + } + + // Try and create nice miters + for (size_t j = 1; j < segments.size(); j++) + { + Segment::CreateMiter(segments[j - 1], segments[j]); + } + + if (layer.IsClosedChain(i)) + { + Segment::CreateMiter(segments.back(), segments.front()); + } + + for (size_t j = 0; j < segments.size(); j++) + { + if (!segments[j].IsEmpty()) + { + segments[j].AddTriangles(coords, miterDirections); + } + } + } + } + + if (!coords.empty()) + { + verticesCount_ = coords.size() / COMPONENTS_POSITION; + + context_.MakeCurrent(); + glGenBuffers(2, buffers_); + + glBindBuffer(GL_ARRAY_BUFFER, buffers_[0]); + glBufferData(GL_ARRAY_BUFFER, sizeof(float) * coords.size(), &coords[0], GL_STATIC_DRAW); + + glBindBuffer(GL_ARRAY_BUFFER, buffers_[1]); + glBufferData(GL_ARRAY_BUFFER, sizeof(float) * miterDirections.size(), &miterDirections[0], GL_STATIC_DRAW); + } + } + + + OpenGLLinesProgram::Data::~Data() + { + if (!IsEmpty()) + { + context_.MakeCurrent(); + glDeleteBuffers(2, buffers_); + } + } + + + GLuint OpenGLLinesProgram::Data::GetVerticesBuffer() const + { + if (IsEmpty()) + { + throw Orthanc::OrthancException(Orthanc::ErrorCode_BadSequenceOfCalls); + } + else + { + return buffers_[0]; + } + } + + + GLuint OpenGLLinesProgram::Data::GetMiterDirectionsBuffer() const + { + if (IsEmpty()) + { + throw Orthanc::OrthancException(Orthanc::ErrorCode_BadSequenceOfCalls); + } + else + { + return buffers_[1]; + } + } + + + OpenGLLinesProgram::OpenGLLinesProgram(OpenGL::IOpenGLContext& context) : + context_(context) + { + + context_.MakeCurrent(); + + program_.reset(new OpenGL::OpenGLProgram); + program_->CompileShaders(VERTEX_SHADER, FRAGMENT_SHADER); + } + + + void OpenGLLinesProgram::Apply(const Data& data, + const AffineTransform2D& transform, + bool antialiasing, + bool scaleIndependantThickness) + { + if (!data.IsEmpty()) + { + context_.MakeCurrent(); + program_->Use(); + + GLint locationPosition = program_->GetAttributeLocation("a_position"); + GLint locationMiterDirection = program_->GetAttributeLocation("a_miter_direction"); + + float m[16]; + transform.ConvertToOpenGLMatrix(m, context_.GetCanvasWidth(), context_.GetCanvasHeight()); + + glUniformMatrix4fv(program_->GetUniformLocation("u_matrix"), 1, GL_FALSE, m); + glUniform3f(program_->GetUniformLocation("u_color"), + data.GetRed(), data.GetGreen(), data.GetBlue()); + + glBindBuffer(GL_ARRAY_BUFFER, data.GetVerticesBuffer()); + glEnableVertexAttribArray(locationPosition); + glVertexAttribPointer(locationPosition, COMPONENTS_POSITION, GL_FLOAT, GL_FALSE, 0, 0); + + glBindBuffer(GL_ARRAY_BUFFER, data.GetMiterDirectionsBuffer()); + glEnableVertexAttribArray(locationMiterDirection); + glVertexAttribPointer(locationMiterDirection, COMPONENTS_MITER, GL_FLOAT, GL_FALSE, 0, 0); + + glUniform1i(program_->GetUniformLocation("u_antialiasing"), (antialiasing ? 1 : 0)); + + const double zoom = transform.ComputeZoom(); + const double thickness = data.GetThickness() / 2.0; + const double aliasingBorder = 2.0; // Border for antialiasing ramp, in pixels + assert(aliasingBorder > 0); // Prevent division by zero with "t1" + + if (scaleIndependantThickness) + { + if (antialiasing) + { + double t1 = std::max(thickness, aliasingBorder); + double t0 = std::max(0.0, thickness - aliasingBorder); + + glUniform1f(program_->GetUniformLocation("u_thickness"), t1 / zoom); + glUniform1f(program_->GetUniformLocation("u_antialiasing_start"), t0 / t1); + } + else + { + glUniform1f(program_->GetUniformLocation("u_thickness"), thickness / zoom); + } + } + else + { + if (antialiasing) + { + double t1 = std::max(thickness, aliasingBorder / zoom); + double t0 = std::max(0.0, thickness - aliasingBorder / zoom); + + glUniform1f(program_->GetUniformLocation("u_thickness"), t1); + glUniform1f(program_->GetUniformLocation("u_antialiasing_start"), t0 / t1); + } + else + { + glUniform1f(program_->GetUniformLocation("u_thickness"), thickness); + } + } + + if (antialiasing) + { + glEnable(GL_BLEND); + glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA); + glDrawArrays(GL_TRIANGLES, 0, data.GetVerticesCount()); + glDisable(GL_BLEND); + } + else + { + glDrawArrays(GL_TRIANGLES, 0, data.GetVerticesCount()); + } + + glDisableVertexAttribArray(locationPosition); + glDisableVertexAttribArray(locationMiterDirection); + } + } + } +}