MB86296 Datasheet, PDF (106/352 Pages) Fujitsu Component Limited. – PCI Graphics Controller Specification

FUJITSU LIMITED PRELIMINARY AND CONFIDENTIAL
9.1.4 View port transformation (NDC→DC coordinate transformation)
The geometry engine transforms “XYZ” of the “NDC” coordinate system to the “DC” coordinate system
according to the transformation coefficient specified by G_ViewPort and G_DepthRange.
“X_Scaling,X_Offset” and “Y_Scaling,Y_Offset” are coefficients to be mapped finally to Frame Buffer.
Xdc and Ydc must be included within the drawing input range (-4096 to 4095). “Z_Scaling” and
“Z_Offset” are coefficients to be mapped finally to “Z Buffer”. “Zdc” must be included within the “Z
Buffer” range (0 to 65535).
DC: Device Coordinates
Xdc = X_Scaling*Xndc + X_Offset
Ydc = Y_Scaling*Yndc + Y_Offset
Zdc = Z_Scaling*Zndc + Z_Offset
9.1.5 View volume clipping
Expression for determination
The expression for determining the CORAL view volume clipping is shown below. W clipping is
intended to prevent the overflow caused by 1/W.
Xmin*Wcc ≤ Xcc ≤ Xmax*Wcc
Ymin*Wcc ≤ Ycc ≤ Ymax*Wcc
Zmin*Wcc ≤ Zcc ≤ Zmax*Wcc
Wmin ≤ Wcc
Note: Xmin, Xmax, Ymin, Ymax, Zmin, Zmax, and Wmin are the clip boundary values set by the
G_ViewVolumeXYClip/ZClip/WClip packet.
Clipping-on/-off
View volume clipping-on/-off can be switched by using the clip boundary values set by the
G_ViewVolumeXYClip/Zclip/WClip packet. To switch view volume clipping to off, set the maximum
and minimum values of the geometry data format (IEEE single-precision floating point(*1)) in the
“Clip.max” value(*2) and “Clip.min” value(*3), respectively. In this case, ‘All coordinate
transformation results’ can be evaluated as within view volume range, making it possible to obtain
the effect of view volume clipping-off.
This method is valid only when W clipping does not occur. When a clip boundary value (Wmin)
that causes W clipping to occur is set, clipping is also performed for each clip area. Consequently,
set an appropriate clip boundary value for Clip. Max value. and Clip. Min value., respectively.
If other values are set in “Clip.max” and Clip.min, view volume clipping-on operates. The
coordinate transformation result is always compared with the values set in “Clip.max” and
“Clip.min”.
*1: Maximum value = 0x7f7fffff, minimum value = 0xff7fffff
*2: Xmin,Ymin, Zmin, Wmin
*3: Xmax, Ymax, Zmax
MB86296S<Coral-PA>
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Specification Manual Rev0.1