 			uniform sampler2D waterHeights;
 			uniform sampler2D terrainHeights;
 			uniform float x;
+			uniform float deltaTime;
 			
 			float terrain(float2 uv) {
 				return tex2D(terrainHeights, uv);

			}
			
			float flux(float2 uv1, float2 uv2) {
				return max(0,x*(terrain(uv1)+water(uv1)-terrain(uv2)-water(uv2)));
			}
			
            float4 frag(v2f_img i) : SV_Target {

        		float left_flux = flux(i.uv, left);
        		float right_flux = flux(i.uv, right);           	
            	
            	//if up_flux + down_flux + left_flux + right_flux > water(i.uv)
            	
            	// calculate k
            
                return float4(up_flux, down_flux, left_flux, right_flux);
            }
