Model transform

GDDM V3R2 Base Application Programming Reference

Model transform

GDDM V3R2 Base Application Programming Reference
SC33-0868-02

The Model Transform order is a transformation matrix.


Fld len	Content	Meaning
1	*Set* X'24'	Model Transform order code
	*Push* & *set* X'64'	Model Transform order code
1	LEN	Length of following data
1	X'00'	Reserved
1	Flags:
	B'`000000..`'	Reserved
	B'`......00`'	Replace
	B'`......01`'	Postmultiply
	B'`......10`'	Premultiply (equivalent to GSSTFM preemptive)
	Other bit patterns	Not supported.
2	MASK	Load Mask Values
N	MATRIX	Transformation Matrix

Note: A segment transformation is defined by a matrix


                               
            | M11 M12 M13 M14 |
            | M21 M22 M23 M24 |
     M =    |                 |
            | M31 M32 M33 M34 |
            | M41 M42 M43 M44 |
            |                 |

which is applied to primitives p to give p' as follows:


     (x',y',z',1) = (x,y,z,1).M

The GDF order defines the matrix elements in the order

M11,M12,...,M14,M21,...,M44

This differs from the GSSTFM call, which specifies the matrix elements in the order

M11,M21,M31,M12,...,M33

The MASK field identifies those elements of the transformation defined by the MATRIX field. The bits within MASK correspond to, in order, elements

M11,M12,...,M14,M21,...M44

of the transformation. The values provided in MATRIX correspond, in order, to those elements of the transformation identified by bits set to 1 within MASK. All uninitialized values within the transformation matrix are set from the identity transformation.

Only elements M11, M12, M21, M22, M41, and M42 are processed by GDDM. All other elements must be zero or one (as in the identity matrix).

The transformation elements may be specified in one-byte, two-byte, or four-byte form, corresponding to the data type GDF coordinates.

The fixed-point representation of the matrix elements is: M41, M42 are twos complement numbers (8-bit or 16-bit). Elements M11, M12, M21, and M22 are twos complement numbers in the following form:


     SB.bb bbbb (bbbb bbbb)

   where S is the sign bit (1 = negative), B is the integer bit, and b the
   fractional bits (6 or 14 of them).

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