Graphics Reference
In-Depth Information
void
CModel::ComputeTigerPosition(
float
sec) {
// Transform operator of the tiger scene node
UWB
_
XformInfo xf = m
_
TigerNode->GetXformInfo();
// user rotation settings (
R
)
mat3
tigerM = xf.GetRotation();
// forward direction in tiger oc space (
V
o
f
)
A:
B:
vec3
tigerFront(0,0,-1);
// forward direction in WC (
V
w
f
)
Source file.
Model
_
MoveTiger.cpp
file
vec3
currentFront = tigerFront
*
tigerM;
// speed of 0.4 unit per second
in
the
Model
folder
of
the
D3D
_
Orientation
project.
C:
float
tigerSpeed = 0.4f;
// tiger's current velocity (
V
t
)
vec3
tigerVelocity = currentFront
*
tigerSpeed;
// sets the velocity to the scene node
m
_
TigerNode->SetVelocity(tigerVelocity);
// computes:
P
t
=
P
t
+(
V
t
×
sec
)
m
_
TigerNode->MoveNodeByVelocity(sec);
D:
}
Listing 16.13.
Moving the tiger forward.
Now, to move the tiger forward, we compute a forward-moving velocity
V
t
,
V
wc
V
t
=
×
speed
,
f
where speed is some constant, and we change the tiger position
P
t
:
P
t
=
P
t
+
V
t
.
Listing 16.13 shows the implementation of moving the tiger in its forward direc-
tion. The
ComputeTigerPosition()
function is called from
CModel::Update
Simulation()
during each timer update event. We can see a straightforward im-
plementation of the mathematics we have derived. At label A, we obtain a matrix
representation of the user's rotation settings
R
, the forward direction in WC space
V
wc
f
is computed at label B, the forward velocity
V
t
is computed at label C, and
finally, the tiger's new position
P
t
is computed at label D.
Aiming with a rotation matrix.
Enable plane aiming by checking the “Aim
Plane At Tiger” checkbox. Notice that the orientation of the purple plane is
changed immediately to face toward the tiger. Now, enable the movement of the
tiger by checking the “Move Tiger” checkbox and navigate the tiger. Observe that
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