Game Development Reference
In-Depth Information
Figure 6.5
With a negative slope and a negative y-intercept, the line slopes toward quadrant IV.
Negative Shifts
You can define linear equations so that the y-intercept is negative. As Figure 6.5
illustrates, when you combine a negative slope value with a negative y-intercept,
the line shifts down on the
y
axis and slopes downward toward quadrant IV. It
no longer passes through quadrant I. When you set the slope to
1 and the
y-intercept to
2, then the line crosses the
y
axis at
2. The value of
y
when
x
equals 2 is
4. On the other side of the
y
axis, when
x
is equal to
2,
y
is equal to 0.
Multiplying a negative value of
x
by the negative slope generates a positive value,
so the value of
y
continues to increase as the negative values of
x
increase.
