show t value along edge for selection

Author: nmwsharp

include/polyscope/curve_network.h

@@ -39,6 +39,7 @@ struct QuantityTypeHelper<CurveNetwork> {
 struct CurveNetworkPickResult {
   CurveNetworkElement elementType; // which kind of element did we click
   int64_t index;                   // index of the clicked element
+  float tEdge = -1;                // if the pick is an edge, the t-value in [0,1] along the edge
 };
 
 class CurveNetwork : public QuantityStructure<CurveNetwork> {
@@ -191,8 +192,8 @@ class CurveNetwork : public QuantityStructure<CurveNetwork> {
   float computeRadiusMultiplierUniform();
 
   // Pick helpers
-  void buildNodePickUI(size_t nodeInd);
-  void buildEdgePickUI(size_t edgeInd);
+  void buildNodePickUI(const CurveNetworkPickResult& result);
+  void buildEdgePickUI(const CurveNetworkPickResult& result);
 
   // === Quantity adder implementations
   // clang-format off

include/polyscope/elementary_geometry.h

@@ -0,0 +1,15 @@
+// Copyright 2017-2023, Nicholas Sharp and the Polyscope contributors. https://polyscope.run
+
+#pragma once
+
+#include <complex>
+#include <tuple>
+
+#include <glm/glm.hpp>
+
+namespace polyscope {
+
+float computeTValAlongLine(glm::vec3 queryP, glm::vec3 lineStart, glm::vec3 lineEnd);
+
+
+}

src/CMakeLists.txt

@@ -187,6 +187,7 @@ SET(SRCS
   slice_plane.cpp
   weak_handle.cpp
   marching_cubes.cpp
+  elementary_geometry.cpp
 
   ## Structures
 
@@ -283,6 +284,7 @@ SET(HEADERS
   ${INCLUDE_ROOT}/curve_network_vector_quantity.h
   ${INCLUDE_ROOT}/disjoint_sets.h
   ${INCLUDE_ROOT}/depth_render_image_quantity.h
+  ${INCLUDE_ROOT}/elementary_geometry.h
   ${INCLUDE_ROOT}/file_helpers.h
   ${INCLUDE_ROOT}/floating_quantity_structure.h
   ${INCLUDE_ROOT}/floating_quantity.h

src/curve_network.cpp

@@ -2,6 +2,7 @@
 
 #include "polyscope/curve_network.h"
 
+#include "polyscope/elementary_geometry.h"
 #include "polyscope/pick.h"
 #include "polyscope/polyscope.h"
 #include "polyscope/render/engine.h"
@@ -348,17 +349,18 @@ void CurveNetwork::buildPickUI(const PickResult& rawResult) {
 
   switch (result.elementType) {
   case CurveNetworkElement::NODE: {
-    buildNodePickUI(result.index);
+    buildNodePickUI(result);
     break;
   }
   case CurveNetworkElement::EDGE: {
-    buildEdgePickUI(result.index);
+    buildEdgePickUI(result);
     break;
   }
   };
 }
 
-void CurveNetwork::buildNodePickUI(size_t nodeInd) {
+void CurveNetwork::buildNodePickUI(const CurveNetworkPickResult& result) {
+  int32_t nodeInd = result.index;
 
   ImGui::TextUnformatted(("node #" + std::to_string(nodeInd) + "  ").c_str());
   ImGui::SameLine();
@@ -379,12 +381,14 @@ void CurveNetwork::buildNodePickUI(size_t nodeInd) {
   ImGui::Indent(-20.);
 }
 
-void CurveNetwork::buildEdgePickUI(size_t edgeInd) {
+void CurveNetwork::buildEdgePickUI(const CurveNetworkPickResult& result) {
+  int32_t edgeInd = result.index;
+
   ImGui::TextUnformatted(("edge #" + std::to_string(edgeInd) + "  ").c_str());
   ImGui::SameLine();
-  size_t n0 = edgeTailInds.getValue(edgeInd);
-  size_t n1 = edgeTipInds.getValue(edgeInd);
-  ImGui::TextUnformatted(("  " + std::to_string(n0) + " -- " + std::to_string(n1)).c_str());
+  int32_t n0 = edgeTailInds.getValue(edgeInd);
+  int32_t n1 = edgeTipInds.getValue(edgeInd);
+  ImGui::Text("  %d -- %d     t_select = %.4f", n0, n1, result.tEdge);
 
   ImGui::Spacing();
   ImGui::Spacing();
@@ -481,10 +485,10 @@ CurveNetworkPickResult CurveNetwork::interpretPickResult(const PickResult& rawRe
 
     // compute the t \in [0,1] along the edge
     int32_t iStart = edgeTailInds.getValue(result.index);
-    int32_t iEnd= edgeTipInds.getValue(result.index);
+    int32_t iEnd = edgeTipInds.getValue(result.index);
     glm::vec3 pStart = nodePositions.getValue(iStart);
     glm::vec3 pEnd = nodePositions.getValue(iEnd);
-
+    result.tEdge = computeTValAlongLine(rawResult.position, pStart, pEnd);
   } else {
     exception("Bad pick index in curve network");
   }

src/elementary_geometry.cpp

@@ -0,0 +1,22 @@
+// Copyright 2017-2023, Nicholas Sharp and the Polyscope contributors. https://polyscope.run
+
+#include "polyscope/elementary_geometry.h"
+
+
+#include <cmath>
+#include <vector>
+
+#include <glm/gtx/norm.hpp>
+
+namespace polyscope {
+
+float computeTValAlongLine(glm::vec3 queryP, glm::vec3 lineStart, glm::vec3 lineEnd) {
+  glm::vec3 lineVec = lineEnd - lineStart;
+  glm::vec3 queryVec = queryP - lineStart;
+  float len2 = glm::length2(lineVec);
+  float t = glm::dot(queryVec, lineVec) / len2;
+  t = glm::clamp(t, 0.f, 1.f);
+  return t;
+}
+
+} // namespace polyscope