added ray-inf-cylinder intersection, not really tested, possibly buggy.

core/FileSystemUtils.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Linq;
+using System.IO;
+
+namespace g3
+{
+    public static class FileSystemUtils
+    {
+        static public bool CanAccessFolder(string sPath)
+        {
+            try {
+                Directory.GetDirectories(sPath);
+            } catch (Exception) {
+                return false;
+            }
+            return true;
+        }
+
+
+        static public bool IsValidFilenameCharacter(char c)
+        {
+            return Path.GetInvalidFileNameChars().Contains(c) == false;
+        }
+        static public bool IsValidFilenameString(string s)
+        {
+            for (int i = 0; i < s.Length; ++i)
+                if (Path.GetInvalidFileNameChars().Contains(s[i]))
+                    return false;
+            return true;
+        }
+
+    }
+}

math/Vector3f.cs

@@ -71,6 +71,19 @@ public float Dot(Vector3f v2)
             return v[0] * v2[0] + v[1] * v2[1] + v[2] * v2[2];
         }
 
+        public Vector3f Cross(Vector3f v2)
+        {
+            return new Vector3f(
+                v[1] * v2.v[2] - v[2] * v2.v[1],
+                v[2] * v2.v[0] - v[0] * v2.v[2],
+                v[0] * v2.v[1] - v[1] * v2.v[0]);
+        }
+
+        public float SqrDistance(Vector3f v2)
+        {
+            float a = (v[0] - v2[0]), b = (v[1] - v2[1]), c = (v[2] - v2[2]);
+            return a * a + b * b + c * c;
+        }
 
 
         public void Set(Vector3f o)

queries/RayIntersection.cs

@@ -41,5 +41,44 @@ public static bool SphereSigned(Vector3f vOrigin, Vector3f vDirection, Vector3f
 
             return true;
         }
+
+
+
+
+        public static bool InfiniteCylinder(Vector3f vOrigin, Vector3f vDirection, Vector3f vCylOrigin, Vector3f vCylAxis, float fRadius, out float fRayT)
+        {
+            bool bHit = InfiniteCylinderSigned(vOrigin, vDirection, vCylOrigin, vCylAxis, fRadius, out fRayT);
+            fRayT = Math.Abs(fRayT);
+            return bHit;
+        }
+        public static bool InfiniteCylinderSigned(Vector3f vOrigin, Vector3f vDirection, Vector3f vCylOrigin, Vector3f vCylAxis, float fRadius, out float fRayT)
+        {
+            // [RMS] ugh this is shit...not even sure it works in general, but works for a ray inside cylinder
+
+            fRayT = 0.0f;
+
+
+            Vector3f AB = vCylAxis;
+            Vector3f AO = (vOrigin - vCylOrigin);
+            if (AO.SqrDistance(AO.Dot(AB) * AB) > fRadius * fRadius)
+                return false;
+
+            Vector3f AOxAB = AO.Cross(AB);
+            Vector3f VxAB = vDirection.Cross(AB);
+            float ab2 = AB.Dot(AB);
+            float a = VxAB.Dot(VxAB);
+            float b = 2 * VxAB.Dot(AOxAB);
+            float c = AOxAB.Dot(AOxAB) - (fRadius * fRadius * ab2);
+
+            double discrim = b * b - 4 * a * c;
+            if (discrim <= 0)
+                return false;
+            discrim = Math.Sqrt(discrim);
+            fRayT = (-b - (float)discrim) / (2 * a);
+            //float t1 = (-b + (float)discrim) / (2 * a);
+
+            return true;
+        }
+
     }
 }