Surface entities are a number of faces joined together to give the impression of roundness (using soft edges). Although the individual planar faces that make up a curved face set are still separate entities, they can act like a single group when selected or painted.
There are three types of surfaces, though the Entity Info dialog box will recognize each as just a Surface entity:
- Arc surface. An arc surface is generated when a face with an Arc entity has one or more of its edges extruded (usually with the Push/Pull tool).
- Cylindrical surface. A cylindrical surface is similar to an arc surface, but is generated when a circular face is extruded to form a cylinder.
- Polyface surface. A polyface surface is generated when a face with a Polyline Curve entity has one or more of its edges extruded (usually with the Push/Pull tool). You can also create one manually by softening edges with the Erase tool or using the Soften/Smooth Control. Polyface surfaces do not have special editable properties, but respond to tool operations as a single entity.
The following image contains the three types of surfaces, an arc surface, cylindrical surface, and polyface surface, from left to right.