25. The method of claim 22 , wherein material properties include at least one of material type, density, friction and bounce parameters such as coefficient of restitution.
25. The method of claim 22 , wherein material properties include at least one of material type, density, friction and bounce parameters such as coefficient of restitution. 28. The method of claim 25 , wherein a first distinctive visual feature has associated semantic information including default material properties of a model component and a second distinctive visual feature has associated second semantic information including alternative material properties of the model component that differ from and override at least some of the default material properties.