Orthographic Projection Chapter 2

Orthographic Projection Overview

• Orthographic projection graphically represents an object's true shape through two or more views on perpendicular planes.
• Assumes the observer is directly in front of the object, where the line of sight is perpendicular to the projected view.

Specific Objectives

• Explain the concept of orthographic projection.
• Identify the different planes of projection: Frontal, Horizontal, and Profile.
• Describe and apply standard line practices for orthographic projection.
• Draw the necessary views based on principles of orthographic projection.

Planes of Projection

• Frontal Plane: Projects the front view of an object.
• Horizontal Plane: Projects the top view of an object.
• Profile Plane: Projects the side views of an object.

Regular Views of an Object

• Six regular views exist:
  • Front View: Shows the characteristic shape; irregular shapes outline this view.
  • Top View: Located above the front view.
  • Right Side View: Located to the right of the front view.
  • Left Side View: Located to the left of the front view.
  • Rear View: Found at the back of the front view.
  • Bottom View: Located below the top view.
• Principal views focus on the front, top, and right-side views.

Three Space Dimensions

• Width: Measured from left to right between two profile planes.
• Depth: Measured from front to rear between two frontal planes.
• Height: Measured from bottom to top between two horizontal planes.
• Each view displays only two of these dimensions (e.g., front view shows width and height).

Principles of Orthographic Projection

• Points project as points in all planes.
• Lines parallel to a plane appear in true lengths; perpendicular lines appear as points.
• Inclined lines appear foreshortened, and no line may project longer than its true length.
• Surfaces parallel appear in true size and shape; perpendicular surfaces appear as edges.
• Surfaces inclined retain shape but are portrayed smaller.
• Top view is drawn directly above the front view; both views should be vertically aligned.
• The depth of both top and side views remains equal.

Selection of Views

• Orthographic projection aims to accurately describe an object's shape using different views.
• Although objects can have six views, not all are necessary to describe shape.
• Select views based on:
  • Characteristic shapes or outlines that best represent the object.
  • Normal use positioning, whether vertically or horizontally aligned.
  • Views that minimize hidden lines for clarity and ease of understanding.