Intel 815 manual Gfxrenderstatemaplodcontrol, Opcode 4h

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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13.10.GFXRENDERSTATE_MAP_LOD_CONTROL

The Level-of-Detail dither weight and bias can be associated with each map using the following instruction.

Figure 37. State Variable Relationships

Coordinate Sets

Map Information

Texels

Blending Stages

Dword	Bit	Description
0	31:29	Client : 03h – Rendering Engine
	28:24	3DState16 : 1Ch
	23:19	Opcode : 4h
	18:17	Reserved: 00h (Additional Maps)
	16	Update Map Index : The valid range is 0–1.
	15:11	Reserved: 00h
	10	Texture LOD Dither Weight Mask : 0 = Do not update; 1 = Update
	9:8	Texture LOD Dither Weight: A 4-bit dither value can be added to the computed and
		biased LOD which softens the transitions between mip-maps. The position or weight of
		the dither value is specified as follows:
		00 = Full dither weight (the dither value has a range of 0.0 – 0.9375)
		01 = ½ dither weight (the dither value has a range of 0.0 – 0.4375)
		10 = ¼ dither weight (the dither value has a range of 0.0 – 0.1875)
		11 = 1/8 dither weight (the dither value has a range of 0.0 – 0.0625)
	7	Texture LOD Bias Mask : 0 = Do not update; 1 = Update
	6:0	Texture LOD Bias : This is a signed value that is added to the LOD when the LOD is
		determined at a textured pixel. This 2’s complement fixed point value has 2 integer bits
		and 4 fractional bits and is signed extended before being added to the LOD. Valid data
		value range from -4.0 to 3.9375. (S2.4) The default value is 0.

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