Filtering; Perspective Correction - Fujitsu MB86R02 Jade-D Hardware Manual

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MB86R02 'Jade-D' Hardware Manual V1.64

Filtering

MB86R02 'Jade-D' supports two texture filtering modes: point filtering and bi-linear filtering.

Point filtering

This mode uses the texture pixel specified by the (S, T) coordinates as they are for drawing. The

nearest pixel in the texture pattern is chosen according to the calculated (S, T) coordinates.

Bi-linear filtering

The four nearest pixels specified with (S, T) coordinate are blended according to the distance from

specified point and used in drawing.

This function corrects the distortion of the 3D perspective in the texture mapping. For this correction,

the 'Q' component of the texture coordinates (Q = 1/W) is set based on the W component of 3D

coordinates of the vertex.

When the texture coordinates are large values, the texture may not be drawn correctly when

perspective correction is performed. This phenomenon occurs due to the precision limitation of the

arithmetical unit for perspective correction. The coordinates for the texture that cannot be drawn

normally vary with the value of the Q component; as a guide, when this value is smaller than –2048 or

larger than 2048, normal drawing results are less likely to be obtained.