Visualising Solid Shapes
Plane shapes having only two measurements, i.e., length and breadth are called two-dimensional shapes (2-D). For example: square, rectangle, circle, etc.
Solid shapes having three measurements, i.e., length, breadth and height (or depth) are called three-dimensional shapes. 3-D objects occupy space. For example, cube, cuboid, cylinder, sphere, pyramid, cone, etc.
The flat surface of a solid is called a face. An edge of an object is a line along which two surfaces of a solid meet. A point that is formed by three or more intersecting edges of a solid is called a vertex.
A net is a 2-dimensional figure which when folded, forms a 3-dimensional figure.
A sketch of a solid shape can be drawn on a flat surface (like paper). It is called the 2D representation of a 3-D solid. The two types of sketches are:
Oblique sketch, in which the shape does not have proportional lengths. Isometric sketch, in which the measurements are kept proportional. It is drawn on an isometric dot sheet.
In viewing a solid shape, some sections may be hidden from the view. Visualization skill is very helpful to find such hidden shapes.
The ways to view different sections of a solid:
By cutting or slicing a solid, which gives the cross-section of the solid.
By observing the 2-D shadow of the 3-D shape.
By observing the front-view, the side-view and the top-view of the solid.