Extra Half Brite (also referred to as Extra-Half-Brite, Extra-Halfbrite, or EHB),[1][2][3][4] is a planar display mode of the Amiga computer.
This mode uses six bit planes (six bits per pixel).[3][5][6] The first five bit planes index 32 colors selected from a 12-bit color space of 4096 possible colors. If the bit on the sixth bit plane is set, the display hardware halves the brightness of the corresponding color component.[7] This way 64 simultaneous colors are possible (32 arbitrary colors plus 32 half-bright components) while using only 32 color registers.[8] The number of color registers is a hardware limitation of pre-AGA chipsets in Amiga computers.
Some contemporary games (Fusion,[9] Defender of the Crown,[10] Agony,[11] Lotus II,[12] or Unreal[13]) and animations (HalfBrite Hill[4]) use EHB mode as a hardware-assisted means to display shadows or silhouettes.[9][14] EHB is often used as general-purpose 64 color mode with its own restrictions.[9][15][16][17]
Some early versions of the first Amiga, the Amiga 1000, sold in the United States, lack the EHB video mode, which is present in all later Amiga models.[4][2]
See also
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References
edit- ^ Mortimore, Eugene P. (1986). Amiga Programmer's Handbook. SYBEX. ISBN 978-0-89588-343-8.
- ^ a b Maher, Jimmy (January 26, 2018). The Future Was Here: The Commodore Amiga. MIT Press. ISBN 978-0-262-53569-4.
- ^ a b "Amiga Hardware Reference Manual: Color Selection in Extra Half Brite (EHB) Mode". Amiga Developer Docs. Retrieved November 19, 2022.
- ^ a b c Sullivan, Kevin (1987). "HalfBrite Hill". Amiga Animations. Blair-Sullivan Computer Graphics & Animation. Retrieved November 19, 2022.
- ^ "The Atari ST and Amiga computing evolution!". Retroshowcase: oldschool game reference!. Retrieved November 19, 2022.
- ^ Peddie, Jon (June 8, 2022). "Amiga (1988)". IEEE Computer Society. Retrieved November 19, 2022.
- ^ Maher, Jimmy (January 26, 2018). The Future Was Here: The Commodore Amiga. MIT Press. ISBN 978-0-262-53569-4.
- ^ Amiga ROM Kernel Reference Manual: Libraries. Addison-Wesley. 1992. ISBN 978-0-201-56774-8.
- ^ a b c "Extra Half Bright (EHB)". Amiga Graphics Archive. Retrieved November 19, 2022.
- ^ "Defender of the Crown - Castle Norman - Amiga Graphics Archive". amiga.lychesis.net. Retrieved April 12, 2023.
- ^ "Agony - Loader 1 - Amiga Graphics Archive". amiga.lychesis.net. Retrieved April 12, 2023.
- ^ "Lotus 2 - Level 1 - Forest - Amiga Graphics Archive". amiga.lychesis.net. Retrieved April 12, 2023.
- ^ "Unreal - Amiga Graphics Archive". amiga.lychesis.net. Retrieved April 12, 2023.
- ^ "Enhanced Graphics - Extra Half-Brite (EHB) Mode". Hall Of Light - The database of Amiga games. Retrieved April 12, 2023.
- ^ "EHB images". Amiga Graphics Archive. Retrieved September 19, 2011.
- ^ Compute. Vol. 11. Small System Services. 1989. pp. 44, 53.
- ^ Kroah (2020). "The Bard's Tale serie - Bard's Tale Construction Set". Kroah's Game Reverse Engineering Page. Retrieved November 19, 2022.