ThreeDimSim is a powerful 3D mechanics simulation and rendering application. 3D scene is defined by script using simple shapes and imported meshes from 3ds dxf and stl files. Mechanics of solid objects are simulated together with dynamic objects like springs and joints. Simulation includes an automatic exact collision detection and collision simulation. Simulation is rendered using an extensive color model using texturing (normal environmental and video) shadow rendering and can be reviewed using different viewpoints. The simulated scene can be exported to a VRML file including the animation. The scene can be exported as a video clip (avi file) as well.