Blitter object
Encyclopedia
A Bob was a graphical element (GEL) first used by the Amiga
computer. Bobs were hardware sprite
-like objects, movable on the screen with the help of the blitter
coprocessor
.
The AmigaOS
GEL system consisted of VSprites, Bobs, AnimComps (animation components) and AnimObs (animation objects), each extending the preceding with additional functionality. While VSprites were a virtualization of hardware sprites Bobs were drawn into a playfield by the blitter, saving and restoring the background of the GEL as required. The Bob with the highest video priority was the last one to be drawn, which made it appear to be in front of all other Bobs.
In contrast to hardware sprites Bobs were not limited in size and number. Bobs required more processing power
than sprites, because they required at least one DMA
memory copy operation to draw them on the screen. Sometimes three distinct memory copy operations were needed: one to save the screen area where the Bob would be drawn, one to actually draw the Bob, and one later to restore the screen background when the Bob moved away.
An AnimComp added animation to a Bob and an AnimOb grouped AnimComps together and assigned them velocity and acceleration.
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
computer. Bobs were hardware sprite
Sprite (computer graphics)
In computer graphics, a sprite is a two-dimensional image or animation that is integrated into a larger scene...
-like objects, movable on the screen with the help of the blitter
Blitter
In a computer system, a blitter is a circuit, sometimes as a coprocessor or a logic block on a microprocessor, that is dedicated to the rapid movement and modification of data within that computer's memory...
coprocessor
Coprocessor
A coprocessor is a computer processor used to supplement the functions of the primary processor . Operations performed by the coprocessor may be floating point arithmetic, graphics, signal processing, string processing, or encryption. By offloading processor-intensive tasks from the main processor,...
.
The AmigaOS
AmigaOS
AmigaOS is the default native operating system of the Amiga personal computer. It was developed first by Commodore International, and initially introduced in 1985 with the Amiga 1000...
GEL system consisted of VSprites, Bobs, AnimComps (animation components) and AnimObs (animation objects), each extending the preceding with additional functionality. While VSprites were a virtualization of hardware sprites Bobs were drawn into a playfield by the blitter, saving and restoring the background of the GEL as required. The Bob with the highest video priority was the last one to be drawn, which made it appear to be in front of all other Bobs.
In contrast to hardware sprites Bobs were not limited in size and number. Bobs required more processing power
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
than sprites, because they required at least one DMA
Direct memory access
Direct memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
memory copy operation to draw them on the screen. Sometimes three distinct memory copy operations were needed: one to save the screen area where the Bob would be drawn, one to actually draw the Bob, and one later to restore the screen background when the Bob moved away.
An AnimComp added animation to a Bob and an AnimOb grouped AnimComps together and assigned them velocity and acceleration.