V part 1 Obtained from a Guildford County workshop-Summer, 2014

Depending upon the software program, the image on the monitor could be a Perspective view, an orthographic view, or a combination.

 3D Studio Max, Rhinoceros, and some other modeling programs open with a four window display showing top, side, and perspective viewports.

 Various veiwports may be formed by viewing angles.  The image viewed depends upon the line of sight of the viewer.  To move across a scene is called panning.  The scene may be rotated about any of its three axes: x, y, and, z using the Orbit tool.  Views may be zoomed which magnifies the image. The size of the object is not increased.

 Perspective mimics the way a human eye works and provides scenes that have a “natural” appearance. Perspective windows are included in all 3D modeling programs.

 In perspective, lines converge at a vanishing point on the horizon. Perspective views typically contain one, two, three vanishing points.  Objects seem to become dimmer as they move away.  In perspective, objects seem to become smaller as they move away and larger as they come closer.

 Perspective viewports can distort space and “fool the eye” when trying to position objects in 3D. It is not a good idea to attempt object placement and alignment using the perspective window alone.

 Orthographic (Parallel Projection) “Ortho” means straight.

 Typically six different views can be produced by orthographic projection:  Top, bottom, front, back, left, and right sides.  Orthographic viewports are extremely useful in the accurate alignment and positioning of objects and features with respect to other features and objects.

 Coordinate systems are used to locate objects in 3D space.  Lines drawn perpendicular to each other for the purpose of measuring transformation are called the axes.  In the 2D Cartesian coordinate system there is a horizontal axis called the X- axis and a vertical called the Y-axis.  In 3D space a third axes is added called the Z-axis.

 Where axes intersect is called the origin  The origin numbers, or coordinates, identify locations in space.  The coordinates of the origin are 0,0 on the 2D plane and 0,0,0 in 3D space.

 Arcs, ellipses, circles, curves, and freehand curves are basic 2D shapes typically provided within modeling programs called SPLINES. Shapes may be combined to create complex objects.

 Parameters affect the size, placement, and orientation of the object.  Typical parameters include center point, radius, height, width, etc. 

 Values provided automatically by the software are called the defaults.

End Part I