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8/22/2019 3D Display Methods - Mod -3
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Three-DimensionalConcepts
Chapter 9
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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.
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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.
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Coordinate Reference
This coordinate reference defines the position andorientation for the plane of the camera film.
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Three-Dimensional Coordinates
x
y
z
x
y
z
Right handed Left handed
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Shading left-handed
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Shading right-handed
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Wireframe
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Three-Dimensional Display Methods
Parallel projection Project points on the object surface along
parallel lines onto the display plane.
Parallel lines are still parallel afterprojection.
Used in engineering and architectural
drawings.
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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 ViewFront View
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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.
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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.
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Three-Dimensional Display Methods Depth cueing
Identify which is the front and which is the back of displayedobjects
For wireframe displays
Vary the intensity of objects according to their distance
from viewing position For the atomsphere
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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.
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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.
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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
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Three-Dimensional Display Methods
Surface rendering Set the surface intensity of
objects according to
Lighting conditions in
the scene Assigned surface
characteristics
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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.
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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
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Three-Dimensional Display Methods
Cutaway view
Remove part of the visible surfaces to show internalstructure.
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Three-dimensional and stereoscopic views