Do not take square root of negative values.

FP exceptions were triggered in unit tests.

FIXES #2092

Signed-off-by: Bram Stolk <[email protected]>

Author: stolk

openvdb/openvdb/math/Stencils.h

@@ -1627,7 +1627,9 @@ class CurvatureStencil: public BaseStencil<CurvatureStencil<GridT, IsSafe>, Grid
         Real alphaM, alphaG, normGrad;
         if (this->curvatures(alphaM, alphaG, normGrad)) {
           const Real mean = alphaM*mInv2Dx/math::Pow3(normGrad);
-          const Real tmp = std::sqrt(mean*mean - alphaG*mInvDx2/math::Pow4(normGrad));
+          const Real base = mean*mean - alphaG*mInvDx2/math::Pow4(normGrad);
+          const Real clampVal = 0;
+          const Real tmp = std::sqrt(std::max(base, clampVal));
           pair.first  = ValueType(mean - tmp);
           pair.second = ValueType(mean + tmp);
         }

openvdb/openvdb/tools/impl/ConvexVoxelizer.h

@@ -389,7 +389,10 @@ class ConvexVoxelizer
     circleBottom(const ValueT& x0, const ValueT& y0,
                  const ValueT& r, const ValueT& x)
     {
-        return y0 - math::Sqrt(math::Pow2(r) - math::Pow2(x-x0));
+        const ValueT base = math::Pow2(r) - math::Pow2(x-x0);
+        return base <= 0
+            ? y0
+            : y0 - math::Sqrt(base);
     }
 
     /// @brief Computes the top y-coordinate of a circle at a given x position.
@@ -402,7 +405,10 @@ class ConvexVoxelizer
     circleTop(const ValueT& x0, const ValueT& y0,
               const ValueT& r, const ValueT& x)
     {
-        return y0 + math::Sqrt(math::Pow2(r) - math::Pow2(x-x0));
+        const ValueT base = math::Pow2(r) - math::Pow2(x-x0);
+        return base <= 0
+            ? y0
+            : y0 + math::Sqrt(base);
     }
 
     /// @brief Computes the bottom z-coordinate of a sphere at a given (x, y) position.
@@ -417,7 +423,10 @@ class ConvexVoxelizer
     sphereBottom(const ValueT& x0, const ValueT& y0, const ValueT& z0,
                  const ValueT& r, const ValueT& x, const ValueT& y)
     {
-        return z0 - math::Sqrt(math::Pow2(r) - math::Pow2(x-x0) - math::Pow2(y-y0));
+	const ValueT base = math::Pow2(r) - math::Pow2(x-x0) - math::Pow2(y-y0);
+        return base <= 0 // Do not take square root of negative numbers.
+            ? z0
+            : z0 - math::Sqrt(base);
     }
 
     /// @brief Computes the top z-coordinate of a sphere at a given (x, y) position.
@@ -432,7 +441,10 @@ class ConvexVoxelizer
     sphereTop(const ValueT& x0, const ValueT& y0, const ValueT& z0,
               const ValueT& r, const ValueT& x, const ValueT& y)
     {
-        return z0 + math::Sqrt(math::Pow2(r) - math::Pow2(x-x0) - math::Pow2(y-y0));
+	const ValueT base = math::Pow2(r) - math::Pow2(x-x0) - math::Pow2(y-y0);
+        return base <= 0 // Do not take square root of negative numbers.
+            ? z0
+            : z0 + math::Sqrt(base);
     }
 
     // ------------ nested classes ------------