HTML and CSS Reference
InDepth Information
Next we create our two points. The first point,
p1
, is close to the middle of the canvas on the
xaxis, and just above the top (
−20
) on the yaxis. The final point,
p2
, is in the same place on
the xaxis, but near the bottom of the canvas (
470
) on the yaxis:
var
var
p1
=
{
x
:
240
,
y
:
20
};
var
var
p2
=
{
x
:
240
,
y
:
470
};
Finally, we create a dynamic object for the
ship
that holds these values:
var
var
ship
=
{
x
:
p1
.
x
,
y
:
p1
.
y
,
endx
:
p2
.
x
,
endy
:
p2
.
y
,
velocityx
:
0
,
velocityy
:
0
};
In
drawScreen()
,oneveryframe,wefirstfindoutthedistancebetweentheshipandtheend
point by subtracting the current
x
and
y
values for the
ship
from the endpoint
x
and
y
values.
The distance will get shorter on each call to
drawScreen()
as the ship moves farther away
from
p1
and gets closer to
p2
. We do this for both
x
and
y
, even though, in our example, only
the
y
value will change as the spaceship gets closer to
p2
:
var
var
dx
=
ship
.
endx

ship
.
x
;
var
var
dy
=
ship
.
endy

ship
.
y
;
When we have the distances, we multiply those values by
easeValue
to get the
x
and
y
velo
cities for the
ship
on this call to
drawScreen()
:
ship
.
velocityx
=
dx
*
easeValue
;
ship
.
velocityy
=
dy
*
easeValue
;
Finally, we apply those values and draw the spaceship to the canvas:
ship
.
x
+=
ship
.
velocityx
;
ship
.
y
+=
ship
.
velocityy
;
context
.
drawImage
(
shipImage
,
ship
.
x
,
ship
.
y
);
Youcantestthisexamplebyexecuting
CH5EX18.html
fromthecodedistributioninyourweb
browser, or by typing in the full code listing shown in
Example 518
.
Example 518. Easing out (landing the ship)
<!doctype html>
<html
<html lang=
"en"
>
<head>
<head>
<meta
<meta charset=
"UTF8"
>
<title>
<title>
CH5EX18: Easing Out (Landing The Ship)
</title>
</title>
<
script src
=
"modernizr.js"
><
/script>
<
script type
=
"text/javascript"
>
window
.
addEventListener
(
'load'
,
eventWindowLoaded
,
false
false
);
var
var
shipImage
;
function
function
eventWindowLoaded
() {