Added cmdSampleIntersectMeshRay.cpp

cpp/SampleCommands/SampleCommands.vcxproj

@@ -108,6 +108,7 @@
     <ClCompile Include="cmdSampleIntepCrvOnSrf.cpp" />
     <ClCompile Include="cmdSampleInterpCurve.cpp" />
     <ClCompile Include="cmdSampleIntersectCrv.cpp" />
+    <ClCompile Include="cmdSampleIntersectMeshRay.cpp" />
     <ClCompile Include="cmdSampleIntersetCrvSrf.cpp" />
     <ClCompile Include="cmdSampleIterateObjects.cpp" />
     <ClCompile Include="cmdSampleJoinSrf.cpp" />

cpp/SampleCommands/SampleCommands.vcxproj.filters

@@ -693,6 +693,9 @@
     <ClCompile Include="cmdSampleTextureMappingEval.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="cmdSampleIntersectMeshRay.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="SampleCommandsApp.h">

cpp/SampleCommands/cmdSampleIntersectMeshRay.cpp

@@ -0,0 +1,83 @@
+#include "stdafx.h"
+
+/*
+Description:
+  Finds the first intersection of a ray with a mesh.
+Parameters:
+  mesh         - [in]   - A mesh to intersect.
+  ray          - [in]   - A ray to be casted.
+  face_indices - [out]  - Faces on mesh that ray intersects (can be nullptr).
+Returns:
+  >= 0.0 parameter along ray if successful. < 0.0 if no intersection found.
+Remarks:
+  The ray may intersect more than one face in cases where the ray hits the edge
+  between two faces or the vertex corner shared by multiple faces.
+*/
+double SampleIntersectMeshRay(const ON_Mesh* mesh, ON_3dRay* ray, ON_SimpleArray<int>* face_indices)
+{
+  double rc = -1.0;
+  if (mesh && ray)
+  {
+    ON_3dVector dir = ray->m_V;
+    const ON_MeshTree* mesh_tree = mesh->MeshTree(true);
+    if (mesh_tree && dir.Unitize())
+    {
+      // increase the range by a factor of 2 so we are confident the
+      // line passes entirely through the mesh
+      double range = mesh_tree->m_bbox.MaximumDistanceTo(ray->m_P) * 2.0;
+      ON_Line line(ray->m_P, ray->m_P + range * dir);
+
+      ON_SimpleArray<ON_CMX_EVENT> hits;
+      mesh_tree->IntersectLine(line, hits);
+      int hit_count = hits.Count();
+      if (hit_count > 0)
+      {
+        ON_SimpleArray<double> tvals;
+        ON_SimpleArray<int> indices;
+        // tmin should be between 0 and 1 for the line
+        double tmin = 100.0;
+        for (int i = 0; i < hit_count; i++)
+        {
+          const ON_CMX_EVENT& e = hits[i];
+          if (e.m_C[0].m_t <= tmin)
+          {
+            tmin = e.m_C[0].m_t;
+            if (face_indices)
+            {
+              tvals.Append(tmin);
+              indices.Append(e.m_M[0].m_face_index);
+            }
+          }
+          if (e.m_type == ON_CMX_EVENT::cmx_overlap && e.m_C[1].m_t <= tmin)
+          {
+            tmin = e.m_C[1].m_t;
+            if (face_indices)
+            {
+              tvals.Append(tmin);
+              indices.Append(e.m_M[1].m_face_index);
+            }
+          }
+        }
+        if (tmin >= 0 && tmin <= 1.0)
+        {
+          if (face_indices)
+          {
+            for (int i = 0; i < tvals.Count(); i++)
+            {
+              if (tvals[i] == tmin)
+                face_indices->Append(indices[i]);
+            }
+          }
+
+          double line_length = line.Length();
+          double ray_length = ray->m_V.Length();
+          if (ray_length > ON_SQRT_EPSILON)
+          {
+            rc = tmin * line_length / ray_length;
+          }
+        }
+      }
+    }
+  }
+  return rc;
+}