Game Development Reference
In-Depth Information
FLOAT Angle
// Angle of rotation measured in radians.
);
cos
0
sin
0
0
1
0
0
Y
sin
0
cos
0
0
0
0
1
The D3DX function to build a y-axis rotation matrix is:
D3DXMATRIX *D3DXMatrixRotationY(
D3DXMATRIX* pOut,
// Result.
FLOAT Angle
// Angle of rotation measured in radians.
);
cos
sin
0
0
sin
cos
0
0
Z
0
0
1
0
0
0
0
1
The D3DX function to build a z-axis rotation matrix is:
D3DXMATRIX *D3DXMatrixRotationZ(
D3DXMATRIX* pOut,
// Result.
FLOAT Angle
// Angle of rotation measured in radians.
);
The inverse of a rotation matrix
R
is its transpose
R
T
=
R
-1
. Such a
matrix is said to be orthogonal.
The Scaling Matrix
Figure 10: Scaling
by one-half units
on the x-axis and
two units on the
y-axis
We can scale a vector
q
x
units on the x-axis,
q
y
units on the y-axis, and
q
z
units on the z-axis by multiplying a vector with the following matrix:
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