Fixing photon ray first intersection filters for lemon/ovus.

Details in the github pull POV-Ray#358 request discussion thread. See especially
comments made in April of 2019. Note, this fixes only one of a layered set
of reasons photon rays can bleed through all or part of ovus and lemon
shapes.

Author: wfpokorny

source/core/shape/lemon.cpp

@@ -67,10 +67,6 @@ namespace pov
 // as it is used only with low power, precision can be high
 const DBL Lemon_Tolerance = 1.0e-10;
 
-// Tolerance used while selecting from solver returned roots.
-// TODO FIXME - can we use EPSILON or a similar more generic constant instead?
-const DBL ROOT_TOLERANCE = 1.0e-4;
-
 
 /*****************************************************************************
 *
@@ -221,9 +217,9 @@ int Lemon::Intersect(const Vector3d& P, const Vector3d& D, LEMON_INT *Intersecti
             vertical = Ipoint[Z];
             if ((vertical >= 0.0) && (vertical <= 1.0))
             {
+                DBL effectiveIRadius = sqrt(Sqr(Ipoint[X]) + Sqr(Ipoint[Y]) + Sqr(Ipoint[Z]-VerticalPosition));
                 horizontal = sqrt(Sqr(Ipoint[X]) + Sqr(Ipoint[Y]));
-                OCSquared = Sqr((horizontal - HorizontalPosition)) + Sqr((vertical - VerticalPosition));
-                if (fabs(OCSquared - r2 ) < ROOT_TOLERANCE)
+                if (effectiveIRadius < inner_radius)
                 {
                     Intersection[i].d = r[n];
                     INormal = Ipoint;

source/core/shape/ovus.cpp

@@ -226,9 +226,9 @@ void Ovus::Intersect_Ovus_Spheres(const Vector3d& P, const Vector3d& D,
         vertical = IPoint[Y];
         if ((vertical > BottomVertical) && (vertical < TopVertical))
         {
+            DBL effectiveIRadius = sqrt(Sqr(IPoint[X]) + Sqr(IPoint[Y]-VerticalPosition) + Sqr(IPoint[Z]));
             horizontal = sqrt(Sqr(IPoint[X]) + Sqr(IPoint[Z]));
-            OCSquared = Sqr((horizontal + HorizontalPosition)) + Sqr((vertical - VerticalPosition));
-            if (fabs(OCSquared - Sqr(ConnectingRadius)) < RootTolerance)
+            if (effectiveIRadius < ConnectingRadius)
             {
                 if (*Depth5 < 0)
                 {