MULTIMEDIA TECHNOLOGY SMM 3001 MEDIA - GRAPHICS

In this chapter how the computer creates, stores, and displays graphic images how the computer creates, stores, and displays graphic images how painting programs allow the user to control computer graphic primitives how painting programs allow the user to control computer graphic primitives the tools and features found in drawing and illustration graphic applications the tools and features found in drawing and illustration graphic applications how graphics software helps to automate creating 3-D images and animations how graphics software helps to automate creating 3-D images and animations

Graphic Images for display) graphic images are composed of pixels for display) graphic images are composed of pixels this type of graphic is called bit-mapped or raster graphics this type of graphic is called bit-mapped or raster graphics the image is stored as a sequence of bits (a) representing the pixel properties (b) the image is stored as a sequence of bits (a) representing the pixel properties (b)

Graphic Images in most bit- mapped images, each pixel requires a sequence of feature bits in most bit- mapped images, each pixel requires a sequence of feature bits the number of bits needed corresponds to the bitplanes for the image the number of bits needed corresponds to the bitplanes for the image

Bitplane A single bit is not sufficient A single bit is not sufficient 4 bits (2 4 =16) are needed for each pixel to code specific value for 16 possible shades 4 bits (2 4 =16) are needed for each pixel to code specific value for 16 possible shades Therefore, 4 bitplanes is required Therefore, 4 bitplanes is required

Graphic Images object-oriented or vector graphics treat the image as a collection of graphic objects such as lines, curves, and figures object-oriented or vector graphics treat the image as a collection of graphic objects such as lines, curves, and figures vector graphics are resolution independent ( images don’t depend on the characteristics of a specific display device) and scalable vector graphics are resolution independent ( images don’t depend on the characteristics of a specific display device) and scalable vector graphics are more easily edited and often more compact in storage vector graphics are more easily edited and often more compact in storage vector graphic images must often be converted to bitmapped images for display vector graphic images must often be converted to bitmapped images for display

Vector Graphics the image is composed of graphic objects (lines, curves, figures, etc.) the image is composed of graphic objects (lines, curves, figures, etc.) each object is defined by its graphic properties each object is defined by its graphic properties these properties may be changed and scaled easily these properties may be changed and scaled easily

Vector Graphics each object occupies a separate layer each object occupies a separate layer layers may be moved, scaled, and arranged in different orders layers may be moved, scaled, and arranged in different orders objects may be deleted and inserted easily objects may be deleted and inserted easily

Graphics Applications Bit-mapped graphics painting programs painting programs Vector graphics drawing programs drawing programs illustration programs illustration programs 3-D modeling and rendering programs 3-D modeling and rendering programs

Painting Programs two-dimensional, bitmapped images/ files two-dimensional, bitmapped images/ files interface based on artwork metaphor interface based on artwork metaphor image (canvas) painted with brushes, pencils, chalk, etc. image (canvas) painted with brushes, pencils, chalk, etc. colors, patterns, and textures selected from palettes colors, patterns, and textures selected from palettes image is divided into foreground and background layers image is divided into foreground and background layers

Painting Programs offer a variety of patterns, textures, and colors offer a variety of patterns, textures, and colors have assorted tools for transforming selected portions of the image have assorted tools for transforming selected portions of the image have tools for creating pixel masks have tools for creating pixel masks

Drawing Programs are simple vector graphic programs are simple vector graphic programs best-suited for basic illustrations best-suited for basic illustrations employ an artwork metaphor for the user interface like painting programs employ an artwork metaphor for the user interface like painting programs an image is a set of graphic objects that are created individually and composed together an image is a set of graphic objects that are created individually and composed together

Illustration Programs are also vector graphic programs are also vector graphic programs generate PostScript (scalable) output generate PostScript (scalable) output have extensive tools, effects, and features have extensive tools, effects, and features used for professional applications used for professional applications

3-D Graphics 3-D graphic programs automate creating images with perspective projection and special effects of lighting and shading 3-D graphic programs automate creating images with perspective projection and special effects of lighting and shading these applications employ either volume-based or surface-based 3-D graphics these applications employ either volume-based or surface-based 3-D graphics

3-D Graphics Volume-based 3-D image is defined by voxels (volume elements) 3-D image is defined by voxels (volume elements) 3-D picture elements having location, color, intensity, transparency, opacity 3-D picture elements having location, color, intensity, transparency, opacity used for scientific visualization and modeling used for scientific visualization and modelingSurface-based 3-D image is composed of objects defined in 3 dimensions 3-D image is composed of objects defined in 3 dimensions regular shapes form the facets or components of each object regular shapes form the facets or components of each object rendering involves adding texture, shading, and lighting effects rendering involves adding texture, shading, and lighting effects

Surface-based 3-D Graphics 3-D image is created in stages model description model description each object is defined in 3 dimensions each object is defined in 3 dimensions scene description scene description objects are placed in scene objects are placed in scene rendering rendering Process of creating the illusion of photorealism Process of creating the illusion of photorealism perspective, and special effects added perspective, and special effects added

Surface-based 3-D Graphics SOLID MODELING - objects are composed of simple 3-D regular solids used as primitive SOLID MODELING - objects are composed of simple 3-D regular solids used as primitive POLYGON-SURFACE MODELING - objects are composed of facets shaped from polygons POLYGON-SURFACE MODELING - objects are composed of facets shaped from polygons WIREFRAME MODELING - objects are composed of facets including parametric curved shapes WIREFRAME MODELING - objects are composed of facets including parametric curved shapes Supported by most applications Supported by most applications

Solid Modelling

Polygon Surface Modelling

Wireframe Modelling

Surface-based 3-D Graphics Rendering techniques Lambert shading Lambert shading Also known as flat shading Also known as flat shading Gouraud shading Gouraud shading Take account the lighting effects on the surrounding surfaces Take account the lighting effects on the surrounding surfaces Phong shading Phong shading Recalculate the illumination model Recalculate the illumination model Ray-tracing Ray-tracing Take account of the light rays that are reflected from the object Take account of the light rays that are reflected from the object

Flat vs Gouraud shading

Phong Shading

Ray Tracing

Texture Mapping Another common technique for determining the appearance of a polygon is to use texture mapping. Another common technique for determining the appearance of a polygon is to use texture mapping. Think of texture mapping like wrapping a present. Each side of the box you are wrapping is a blank polygon. You could paint the box, but it would be very difficult to make it match all the designs on the wrapping paper. Think of texture mapping like wrapping a present. Each side of the box you are wrapping is a blank polygon. You could paint the box, but it would be very difficult to make it match all the designs on the wrapping paper. However, if you take the wrapping paper and tightly cover the box with it, you have completely transformed the box with just a little effort. However, if you take the wrapping paper and tightly cover the box with it, you have completely transformed the box with just a little effort. Texture mapping works the same way. Mapping requires the use of another image. This other image essentially is stretched over the object like a skin. Texture mapping works the same way. Mapping requires the use of another image. This other image essentially is stretched over the object like a skin.

Texture Mapping

Animation animations are composed of individual graphic images called frames animations are composed of individual graphic images called frames Professional-quality animations employ rates of 24 fps and higher Professional-quality animations employ rates of 24 fps and higher frames are displayed at a rate fast enough to be perceived as continuous motion frames are displayed at a rate fast enough to be perceived as continuous motion animation software help to automate the creation of animated graphics animation software help to automate the creation of animated graphics

Animation In-betweening automates the creation of animated sequences In-betweening automates the creation of animated sequences key frames are defined for starting and stopping positions key frames are defined for starting and stopping positions the software calculates the incremental frames the software calculates the incremental frames