Sci Vis I Exam Review

Unit 63D Modeling Concepts

Views

PERSPECTIVE

• Mimics the way the human eye works• Provides “natural” appearance• Parallel lines converge at VANISHING POINTS• Not good for placement or alignment

Views

ORTHOGRAPHIC

• Also called PARALLEL PROJECTION• ORTHO means STRAIGHT• 2D image of a 3D object• 6 Views: top, bottom, front back, left side, right side• Useful for accurate alignment & positioning of

objects

Viewing in 3D Software

PANNING• Moving across a scene (objects don’t move).

ZOOMING• Magnifying the scene (object size doesn’t

change).

Coordinate Systems

• 2D Cartesian coordinate system– Horizontal X Axis– Vertical Y Axis

• 3D coordinate system add Z Axis

• Origin = where axes intersect– 2D origin is (0,0)– 3D origin is (0,0,0)

• Coordinates identify locations in space

Coordinate Systems

• Local (User) Coordinate System– Assigns axes to a particular object

• World (Global) Coordinate System– Assigns axes to a scene

• Relative coordinates– Used to transform an object starting at its current position

• Absolute coordinates– Used to transform an object relative to the origin

Basic Objects in 3D Modeling Programs

3D Shapes• Sphere• Cube or box• Cylinder• Torus (looks like a donut)• Cone• Plane

Basic Objects in 3D Modeling Programs

2D Shapes• Arcs• Ellipses• Circles• Curves• Freehand curves• Polygons (plane figures made with 3 or more straight sides)• Regular polygons (have equal length sides and equal angles)• Splines (curves or polygons that are made of segments that

can be manipulated by control points along the curve_

Parameters

• Typical Parameters– Center Point– Radius– Height– Width– Etc.

• Parameters affect size, placement, & orientation of objects.

Modeling Techniques

BOOLEAN

– Tools or operations used to create objects by combining, subtracting, or determining common intersections• Union or Addition – combine objects into one new object• Subtract or Difference – remove part of all of an object where

objects overlay one another• Intersection – make overlapping parts of objects become the

object

Boolean is named after British Mathematician, George Boole.

Modeling Techniques

EXTRUSION or SWEEPING (LOFTING)

• Allows you to create a 2D shape and then extend it along a path or curve to form a 3D object

• LOFTING is a variation where open or closed curves are spaced parallel to one another and then a surface is created that connects the contours.

• These tools are used for things like modeling boat hulls and terrains.

Modeling Techniques

REVOLVE OR LATHE

• Allows you to create 2D shape and then revolve it around an axis.

• A lathe is a manufacturing tool used to rotate and shape material by bringing cutting tools against the material while it spins.

• Used to model objects such as bowls, bottles, & dishes

• Think about putting clay on a spinning pottery wheel and shaping the clay into an object using tools.

Modeling Techniques

TRANSFORMATIONS OR TRANSFORMS

Actions that scale, rotate, or move objects

• Scale changes size or proportions of an object

• Rotate tilts or changes direction an object is facing. You rotate about an axis and according to degrees.

• Move advances an object from one position to another along one of the axes. Movement may be constrained by a SNAP or GRID setting.

Modeling Techniques

DEFORMATION

Modifies an existing shape.

• Mimic the process of working with a piece of clay.

• Examples are taper, bend, twist, smooth, & stretch.

Other Modeling Techniques

• COPY or CLONE: allow selected objects to be reproduced in their exact size & form

• MIRROR: allow selected shapes to be copied or flipped about a defined center

VIEWING TOOLS

• WIREFRAME: draws objects as edges and vertices, simplest viewpoint

• SOLID: allows the object to appear as a solid

• OTHER: Transparent, Transparent Wireframe, etc.

VIEW NAVIGATION TOOLS

• ZOOM: magnification

• ROTATE: object remains in it’s position within scene while you rotate your point of view

• PANNING (Eye Move): allows you to drag the scene within the viewpoint (window) without changing the positions of objects.

EXPORTING

• Create objects and scenes in one software package and use it in another software package.

• File, Save As in the existing software package to save to the file format of the intended software package.