Rendering; Tiling; Alpha Blending - Fujitsu MB86R02 Jade-D Hardware Manual

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MB86R02 'Jade-D' Hardware Manual V1.64

Rendering

Tiling reads the pixel color from the correlated tiling pattern and maps it onto the polygon. The tiling

determines the pixel on the pattern read by pixel coordinates to be drawn, irrespective of position and

size of primitive. Since the tiling pattern is stored in the texture memory, this function and texture

mapping cannot be used at the same time. Also, the tiling pattern size is limited to within 64 × 64

pixels. (at 16-bit color)

Alpha blending blends the drawn in frame buffer to-be-drawn pixel or pixel already according to the

alpha value set in the alpha register. This function cannot be used simultaneously with logic operation

drawing. It can be used only when the direct color mode (16 bits/pixel) is used. The blended color C is

calculated as shown below when the color of the pixel to be drawn is C

and the alpha value is A:

× A + (1-A) × C

The alpha value is specified as 8-bit data. 00h means alpha value 0% and FFh means alpha value

100%. When the texture mapping function is enabled, the following blending modes can be selected:

Blends post texture mapping color with frame buffer color

Uses MSB of texel color for ON/OFF control:

MSB = 1: Texel color

MSB = 0: Frame buffer color

Stencil alpha

Uses MSB of texel color for α/OFF control:

MSB = 1: Alpha blend texel color and current frame buffer color

MSB = 0: Frame buffer color

Note: MSB of frame buffer is drawn MSB of texel in both stencil and stencil alpha mode.

Therefore in case MSB of texel is MSB=0, a color of frame buffer is frame buffer, but MSB of frame

buffer is set to 0.

Example of Tiling

, the color of frame buffer is C