We present a new surgical robot hardware-in-the-loop simulator, with 3D surgical field reconstruction in RGB-D sensor range, which allows tool-tissue interactions to be presented as haptic feedback and thus provides the situation awareness of unwanted collision. First, the point cloud of the complete surgical environment is constructed from multiple frames of sensor data to avoid the occlusion issue. Then the user selects a region of interest where the robot's tool must avoid (also called forbidden region). The real-time haptic force rendering algorithm computes the interaction force which is then communicated to a haptic device at 1 kHz, to assist the surgeon to perform safe actions. The robot used is a RAVEN II system, RGB-D sensor is used to scan the environment, and two Omni haptic devices provide the 3-DoF haptic force. A registration pipeline is presented to complete the surgical environment point cloud mapping in preoperative surgery planning phase, which improves quality of haptic rendering in the presence of occlusion. Furthermore, we propose a feasible and fast algorithm which extends the existing work on the proxy-based method for haptic rendering between a Haptic Interaction Point (HIP) and a point cloud. The proposed methodology has the potential of improving the safety of surgical robots.