Game Development Reference
In-Depth Information
1.3.5 Wrapping up Rotations
Remember that so far we are able to perform rotations around the origin, however, often
we want to rotate points around an arbitrary point. To do this, we start by translating the
point around which we wish to rotate to the origin, once there, we apply the rotation to the
points we wish to transform and finally we translate them back to their original point.
Figure 19- Rotation must be done relative to the object's local space.
The first step is to translate
p
to the origin, we can do this be translating by the negated
valueof
p
,thisbringsthesquaretotheorigin.Onceattheoriginweapplytherotation R(π/
4) which gives the square a 45 degree clockwise rotation, once rotated, we can translate
back by
p
which brings us back to our initial origin.
The end result of this operation is the rotation about an arbitrary axis as we needed.
1.3.6 Scale
Whendiscussingscale,it'seasiertoimagineashaperatherthanasinglepoint.Scalerefers
to a factor by which we can grow or shrink the given shape. We can do it uniformly across
