SIMD::Float4 lengthMasks = length.MaskNotEqual(kInfinity); // if length is finite, set mask to 0xFFFFFFFF
SIMD::Float4 end = start + (dirAndLen * length) & lengthMasks;

boxMin = SIMD::Min(boxMin, start);
boxMax = SIMD::Max(boxMax, start);
boxMin = SIMD::Min(boxMin, end);
boxMax = SIMD::Max(boxMax, end);