Added silhoutte gui control

src/consts.cu

@@ -55,6 +55,8 @@ __device__ float d_alphaAcumLimit;
 __device__ int d_tfComboSelected;
 __device__ int d_tfComboSelectedColor;
 __device__ float d_opacityConst;
+__device__ bool d_showSilhouettes;
+__device__ float d_silhouettesThreshold;
 
 // ----------------------- Raycasting -----------------------
 __device__ int d_samplesPerPixel;