Planform

In technical drawing and computer graphics, a multiview projection is a technique of illustration by which a standardized series of orthographic two-dimensional pictures is constructed to represent the form of a three-dimensional object. Up to six pictures of an object are produced (called primary views), with each projection plane parallel to one of the coordinate axes of the object. The views are positioned relative to each other according to either of two schemes: first-angle or third-angle projection. In each, the appearances of views may be thought of as being projected onto planes that form a six-sided box around the object. Although six different sides can be drawn, usually three views of a drawing give enough information to make a three-dimensional object. These views are known as front view, top view and end view. Other names for these views include plan, elevation and section.A 3-D view of a beverage-can stove with a cross-section in yellow.A 2-D cross-sectional view of a compression seal.Cutaway of a Porsche 996Cross-section of a jet engineAn image of an object in a box.The same image, with views of the object projected in the direction of sight onto walls using first-angle projection.Similar image showing the box unfolding from around the object.Image showing orthographic views located relative to each other in accordance with first-angle projection. In technical drawing and computer graphics, a multiview projection is a technique of illustration by which a standardized series of orthographic two-dimensional pictures is constructed to represent the form of a three-dimensional object. Up to six pictures of an object are produced (called primary views), with each projection plane parallel to one of the coordinate axes of the object. The views are positioned relative to each other according to either of two schemes: first-angle or third-angle projection. In each, the appearances of views may be thought of as being projected onto planes that form a six-sided box around the object. Although six different sides can be drawn, usually three views of a drawing give enough information to make a three-dimensional object. These views are known as front view, top view and end view. Other names for these views include plan, elevation and section. The terms orthographic projection and orthogonal projection are sometimes reserved specifically for multiview. However, orthographic and orthogonal more correctly refer to the right angle formed between the projection rays and the projection plane, versus the angle formed between the subject of the drawing and the projection plane. Thus, orthographic projections include axonometric or auxiliary views in addition to multiviews. To render each such picture, a ray of sight (also called a projection line, projection ray or line of sight) towards the object is chosen, which determines on the object various points of interest (for instance, the points that are visible when looking at the object along the ray of sight); those points of interest are mapped by an orthographic projection to points on some geometric plane (called a projection plane or image plane) that is perpendicular to the ray of sight, thereby creating a 2D representation of the 3D object. Customarily, two rays of sight are chosen for each of the three axes of the object's coordinate system; that is, parallel to each axis, the object may be viewed in one of 2 opposite directions, making for a total of 6 orthographic projections (or 'views') of the object: