Lecture Autodesk inventor Projection theory Perspective and parallel projections

Projection methods are developed along two lines perspective and parallel. Projection theory comprises the principles used to represent graphically 3D objects and structures on 2D media Drawing more than one face of an object by moving your line of sight relative to the object helps in understanding the 3D form. A line of sight is an imaginary ray of light between an observers eye and the object.

Projection Theory

Perspective and Parallel Projections

Projection Theory

A projection is a mapping of a 3D space onto a 2D subspace

2D space is called the projection plane

Projection also refers to image resulting from such a

mapping

Classification of Projections

O n e - p o i n t

T w o - p o i n t

T h r e e - p o i n t

P e r s p e c t i v e

P r o j e c t i o n

C a v a l i e r

C a b i n e t

G e n e r a l

O b l i q u e

I s o m e t r i c

D i m e t r i c

T r i m e t r i c

A x o n o m e t r i c M u l t i v i e w

O r t h o g r a p h i c

P a r a l l e l

P r o j e c t i o n

P r o j e c t i o n T h e o r y

Common Elements of a Projection System

Center of Projection

(Perspective)/Direction of

Projection (Parallel)

Projection Plane

Object(s) to be projected

Projectors

Some Terminology

Bounding Box = Principal Enclosing Box (PEB)

Center of Projection = Station Point = Viewpoint

of observer

Projection Plane = Viewplane = Picture Plane

Projectors = Sightlines = Line of Sight

Projection Theory

Perspective and Parallel Projections