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Three-Dimensional Concepts

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Chapter 9 Three-Dimensional Concepts Three Dimensional Graphics It is the field of computer graphics that deals with generating and displaying three dimensional ... – PowerPoint PPT presentation

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Title: Three-Dimensional Concepts


1
Three-Dimensional Concepts
  • Chapter 9

2
Three Dimensional Graphics
  • It is the field of computer graphics that deals
    with generating and displaying three dimensional
    objects in a two-dimensional space(eg display
    screen)
  • In addition to color and brightness, a 3-D pixels
    adds a depth property that indicates where the
    point lies on the imaginary z-axis.

3
  • When many 3-D pixels are combined, each with its
    own depth value, the result is a 3-D surface
    called a texture.
  • Objects are created on a 3-D stage where the
    current view is derived from the camera and light
    sources, similar to the real world.

4
Coordinate Reference
  • This coordinate reference defines the position
    and orientation for the plane of the camera film.

5
Three-Dimensional Coordinates
Right handed
Left handed
y
y
z
x
x
z
6
Shading left-handed
7
Shading right-handed
8
Wireframe
9
Three-Dimensional Display Methods
  • Parallel projection
  • Project points on the object surface along
    parallel lines onto the display plane.
  • Parallel lines are still parallel after
    projection.
  • Used in engineering and architectural drawings.

10
  • By selecting different viewing positions, we can
    project visible points on the object onto the
    display plane to obtain different two-dimensional
    views of the object.

Top View
Side View
Front View
11
Three-Dimensional Display Methods
  • Perspective projection
  • Project points to the display plane along
    converging paths.
  • This is the way that our eyes and a camera lens
    form images and so the displays are more
    realistic.

12
  • It has two major characteristics
  • Smaller as their distance from the observer
    increases.
  • Foreshortened the size of an objects dimension
    along the line of sight are relatively shorter
    than dimensions across the line of sight.

13
Three-Dimensional Display Methods
  • Depth cueing
  • Identify which is the front and which is the back
    of displayed objects
  • For wireframe displays
  • Vary the intensity of objects according to their
    distance from viewing position
  • For the atomsphere

14
Three-Dimensional Display Methods
  • Depth Cueing
  • To easily identify the front and back of display
    objects.
  • Depth information can be included using various
    methods.
  • A simple method to vary the intensity of objects
    according to their distance from the viewing
    position. Eg lines closest to the viewing
    position are displayed with the highest
    intensities and lines farther away are displayed
    with decreasing intensities.

15
  • Application is modeling the effect of the
    atmosphere on the pixel intensity of objects.
    More distant objects appear dimmer to us than
    nearer objects due to light scattering by dust
    particles, smoke etc.

16
Three-Dimensional Display Methods
  • Visible line and surface identification
  • Highlight the visible lines or display them in
    different color
  • Display nonvisible lines as dashed lines
  • Remove the nonvisible lines

17
Three-Dimensional Display Methods
  • Surface rendering
  • Set the surface intensity of objects according to
  • Lighting conditions in the scene
  • Assigned surface characteristics

18
  • Lighting specifications include the intensity and
    positions of light sources and the general
    background illumination required for a scene.
  • Surface properties include degree of transparency
    and how rough or smooth the surfaces are to be.

19
Three-Dimensional Display Methods
  • Exploded and Cutaway Views
  • To maintain a hierarchical structures to include
    internal details.
  • These views show the internal structure and
    relationships of the object parts

20
Three-Dimensional Display Methods
  • Cutaway view
  • Remove part of the visible surfaces to show
    internal structure.

21
Three-dimensional and stereoscopic views
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