Virtual reality

Tasks

3D digital model from planes

3D digital model of existing objects

Office work

Field observations

Solid modeling

Photogrammetry

Solid modeling

From 2D elements

Body representation methods

Cross section and a vector (sweeping)

Cross section and a axis of rotation(body of revolution)

Constructive Solid Geometry (CSG)

Boundary representation (BR)

Voxels

Creating 3D world

Difficulties using 2D tools

CAD or special software (3D Studio)

Constructing from views (front view, top view, side view)

Different views at the same time (perspective, front, top, views)

Primitive objects (box, sphere, cone, cylinder, etc.)

3D faces, surfaces (NURBS, Non Uniform Rational B-Splines)

Materials, texture maps, material libraries

NURBS Non Uniform Rational B-Splines

Vizualization

Hidden lines, hidden surfaces

Z-buffer algorithm

ray traceingreflection, transparency

Wireframe

Rendering, light sources,materials

Digital model from photos

object

photo

f

t

x

x’photo II

x”

object

photox’

x

'xx

ft

Constantscale factor

Scale factor changing

Projective transformationPerspective projection between two non parallel planes,collinarity conditionForm with homogeneous coordinatas

Two linear equation for each point

Homogeneous coordinates

Projective transformation

Spatial solution (3D)

Relative orientation, minimum. 6 points onboth photos, reconstructing the relative position

Two photos from different point of views

Absolute orientation, minimum 3 known pointsin the used co-ordinate system

Analytical solution (mathematical projection,adjustment)

Connecting several photos to the model

Measuring control points•Intersection

•Polar points (Direct reflex)

•Laser scanner

•Robotic instruments

VRMLVirtual Reality Markup Language

Free viewers

http://www.parallelgraphics.com/products/cortona/

Cortona VRML Client

VRML 1 1995 (Silicon Graphics' Open Inventor ASCII format)

VRML 2 1996

Cosmo Player

VRML 97 (ISO/IEC-14772-1:1997)

.wrl files (world) Simple text files, platform independent

#VRML V2.0 utf8Shape { geometry Box { size 1 1 1 }}

VRML cont.

VRML features Description of 3D spaces (creation?)Moving objects, animationHyperlinks (html, wrl)Playing sound and video User interactivityProgrammable (java or javascript)

Application areas Visual design, cities, flats, etc. Advertisements, games, artist Education (geometry) Tourism (virtual cities) Simulation, mechanical engineering

Vrml.html