          bool opacityCorrection,
          bool jittering,
          bool clipSphere,
-         bool clipPlane
+         bool clipPlane,
+         bool useSphereAsProbe
         >
 __global__ void render(uint *d_output, const uint width, const uint height, const float dist,
                        const float3 volSizeHalf, const float3 L, const float3 H,

  return ((tmax >= tmin) && (tmax >= 0.0f));
}

__device__ void intersectSphere(const Ray& ray, const float3& center, const float radiusSqr,
                                float* tnear, float* tfar)
{
  Ray r = ray;

             true, // Opacity correction.
             false, // Jittering.
             false, // Clip sphere.
             false, // Clip plane.
             false // Show what's inside the clip sphere.
            ><<<gridSize, blockSize>>>(d_output, width, height,
                                       diagonalVoxels / (float)numSlices,
                                       volSize * 0.5f,
