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 bitplanes (six bits per pixel). [3] [5] [6] The first five bitplanes index 32 colors selected from a 12-bit color space of 4096 possible colors. If the bit on the sixth bitplane 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 only using 32 color registers. [8] The number of color registers is a hardware limitation of pre- AGA chipsets used 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 the aforementioned 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]
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 bitplanes (six bits per pixel). [3] [5] [6] The first five bitplanes index 32 colors selected from a 12-bit color space of 4096 possible colors. If the bit on the sixth bitplane 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 only using 32 color registers. [8] The number of color registers is a hardware limitation of pre- AGA chipsets used 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 the aforementioned 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]