Presentation on theme: "Shared Graphics Skills Cameras and Clipping Planes"— Presentation transcript:
1Shared Graphics Skills Cameras and Clipping Planes Principles of Graphical Representation using Computer Graphics Software3D Representation2D RepresentationShared Graphics SkillsCameras and Clipping Planes
2“Workspace” or “Scene” An Imaginary Cubic BoundaryCartesian Coordinate SystemX, Y, Z Axes0,0,0 is the OriginZ up or Y up
3Geometry Building Blocks Point – also referred to as a vertex – the base geometric element in a computer graphics modeling packageLine – also referred to as Splines in 2D or Edges in 3D – at least 2 vertices, but can contain multiple vertices to become a contiguous string of segmentsClosed Spline or PolylineOpen SplinePlane – in Polygonal modeling / geometry consists of triangular Faces and N-Sided Polygons – contains at least 3 EdgesThe manipulation and plotting of the spatial relationships of these components require a coordinate system.
4Cartesian Coordinate System Points are always plotted in the order of X, Y, ZFrom the Origin, each plotted point is measured negative or positiveQuadrantsRight-Hand Rule2D and 3D is the same, with the Z axis being a value other than zero in 3D.
5Polar Coordinate System Polar Coordinates – Angle then Distance – Positive Counts Counter-Clockwise from Zero
6Absolute vs. Relative Coordinates Absolute Coordinate Input – Each point is always plotted relative to the Origin.Relative Coordinate Input – Each point is plotted relative to the last input.
7Relative Coordinates – Object Coordinate System Using Object Coordinate System (Relative Coordinates) each object has its own originTransformations and manipulations in an Object Coordinate System are relative to the object rather than the world origin.This makes it easier to transform and manipulate the objects
8Graphical Representation The vast majority is 2D representation of 3D objectsTechnical Documentation – Construction Documents, basic communication with peers3D conception –> 2D representation –> 3D realizationComputer Models can be “photographed” – images and line drawings can be generated much faster than can be drawnExtraction Methodology – design in 3D, extract 2D
9Orthographic Projection A means of representing a three-dimensional (3D) object in two dimensions (2D)A perspective projection with a hypothetical viewpoint—e.g., one where the camera lies an infinite distance away from the object and has an infinite focal length, or "zoom". (parallel projection)Multi-view Orthographic ProjectionAxonometric Orthographic ProjectionNon-Orthographic (Perspective)Orthographic
10Multi-View Orthographic Each projection plane is parallel to one of the coordinate axes of the object resulting in visual distortion / abstraction
11Architectural PlanAlso called plan view. a drawing made to scale to represent the top view or a horizontal section of a structure
12Architectural Section A representation of an object as it would appear if cut by a plane, showing its internal structure.
13Architectural Elevation A drawing or design that represents an object or structure as being projected geometrically on a vertical plane parallel to one of its sides.
14Axonometric Axonometric A skewed Orthographic Projection so that multiple sides are visible at oncea three-dimensional object is represented by a drawing having all axes drawn to exact scale, resulting in the optical distortion of diagonals and curvesTrimetric – arbitrary foreshorteningIsometric
15IsometricIsometrica three-dimensional object is represented by a drawing having the horizontal edges of the object drawn usually at a 30° angle and all verticals projected perpendicularly from a horizontal base, all lines being drawn to scale
16Clipping Planes Uses Orthographic Cameras – Relatively Universal Extracts from solids or surfaces alikeUses two planes perpendicular to the focal length of the camera – Near Clipping Plane and Far Clipping PlaneOnly displays graphical information between the near clip and the far clipping plane
18Plotting to File with Clipping Planes The clipping plane method can be used in conjunction with the plot to file method. Plotting to file allows three important options in a single method –Allows rendering – allows the use of hidden line projection to “hide” lines that should be obscured with planes in 3D space.Flattens the drawing – gets rid of the Z dimension and flattens the 3D model to a 2D vector drawingSeparates the line drawings – Drawings can be edited in respect to themselves without adversely altering the model