LowLevel Camera Properties
Camera Properties You Can Set
Camera graphics is based on a group of axes properties that control the position and orientation of the camera.
In general, the camera commands, such as campos
, camtarget
, and camup
, make it unnecessary to access these properties directly.
Property  Description 

CameraPosition  Specifies the location of the viewpoint in axes units. 
CameraPositionMode  In 
CameraTarget  Specifies the location in the axes pointed to by the
camera. Together with the 
CameraTargetMode  In 
CameraUpVector  The rotation of the camera around the viewing axis is defined by a vector indicating the direction taken as up. 
CameraUpVectorMode  In 
CameraViewAngle  Specifies the field of view of the "lens." If you specify a value for CameraViewAngle, MATLAB does not stretchthe axes to fit the figure. 
CameraViewAngleMode  In Setting

Projection  Selects either an orthographic or perspective projection. 
Default Viewpoint Selection
When all the camera mode properties are set to auto
(the
default), MATLAB automatically controls the view, selecting appropriate values based on
the assumption that you want the scene to fill the position rectangle (which is
defined by the width and height components of the axes Position
property).
By default, MATLAB
Sets the
CameraPosition
so the orientation of the scene is the standard MATLAB 2D or 3D view (see theview
command)Sets the
CameraUpVector
so the ydirection is up for 2D views and the zdirection is up for 3D viewsSets the
CameraViewAngle
to the minimum angle that makes the scene fill the position rectangle (the rectangle defined by the axesPosition
property)
This default behavior generally produces desirable results. However, you can change these properties to produce useful effects.
Moving In and Out on the Scene
You can move the camera anywhere in the 3D space defined by the axes. The camera continues to point towards the target regardless of its position. When the camera moves, MATLAB varies the camera view angle to ensure the scene fills the position rectangle.
Moving Through a Scene
You can create a flyby effect by moving the camera through the scene. To do this,
continually change CameraPosition
property, moving it toward
the target. Because the camera is moving through space, it turns as it moves
past the camera target. Override the MATLAB automatic resizing of the scene each time you move the camera by
setting the CameraViewAngleMode
to
manual
.
If you update the CameraPosition
and the
CameraTarget
, the effect is to pass through the scene
while continually facing the direction of movement.
If the Projection
is set to
perspective
, the amount of perspective distortion
increases as the camera gets closer to the target and decreases as it gets
farther away.
Example — Moving Toward or Away from the Target
To move the camera along the viewing axis, you need to calculate new
coordinates for the CameraPosition
property. This is
accomplished by subtracting (to move closer to the target) or adding (to move
away from the target) some fraction of the total distance between the camera
position and the camera target.
The function movecamera
calculates a new
CameraPosition
that moves in on the scene if the argument
dist
is positive and moves out if dist
is negative.
function movecamera(dist) %dist in the range [1 1] set(gca,'CameraViewAngleMode','manual') newcp = cpos  dist * (cpos  ctarg); set(gca,'CameraPosition',newcp) function out = cpos out = get(gca,'CameraPosition'); function out = ctarg out = get(gca,'CameraTarget');
Setting the CameraViewAngleMode
to
manual
can cause an abrupt change in the aspect
ratio.
Making the Scene Larger or Smaller
Adjusting the
CameraViewAngle
property makes the view of the scene larger or
smaller. Larger angles cause the view to encompass a larger area, thereby making the
objects in the scene appear smaller. Similarly, smaller angles make the objects
appear larger.
Changing CameraViewAngle
makes the scene larger or smaller
without affecting the position of the camera. This is desirable if you want to zoom in without moving the viewpoint past objects that will then no
longer be in the scene (as could happen if you changed the camera position). Also,
changing the CameraViewAngle
does not affect the amount of
perspective applied to the scene, as changing CameraPosition
does
when the figure Projection
property is set to
perspective
.
Revolving Around the Scene
You can use the view
command to revolve the viewpoint about the
zaxis by varying the azimuth, and about the azimuth by
varying the elevation. This has the effect of moving the camera around the scene
along the surface of a sphere whose radius is the length of the viewing axis. You
could create the same effect by changing the CameraPosition
, but
doing so requires you to perform calculations that MATLAB performs for you when you call view
.
For example, the function orbit
moves the camera
around the
scene.
function orbit(deg) [az, el] = view; rotvec = 0:deg/10:deg; for i = 1:length(rotvec) view([az+rotvec(i) el]) drawnow end
Rotation Without Resizing
When CameraViewAngleMode
is auto
,
MATLAB calculates the CameraViewAngle
so that the scene is
as large as can fit in the axes position rectangle. This causes an apparent size
change during rotation of the scene. To prevent resizing during rotation, you need
to set the CameraViewAngleMode
to manual
(which happens automatically when you specify a value for the
CameraViewAngle
property). To do this in the
orbit
function, add the statement
set(gca,'CameraViewAngleMode','manual')
Rotation About the Viewing Axis
You can change the orientation of the scene by specifying the direction defined as
up. By default, MATLAB defines up as the yaxis in
2D views (the CameraUpVector
is [0 1 0]
)
and the zaxis for 3D views (the
CameraUpVector
is [0 0 1]
). However, you
can specify up as any arbitrary direction.
The vector defined by the CameraUpVector
property forms one
axis of the camera's coordinate system. Internally, MATLAB determines the actual orientation of the camera up vector by
projecting the specified vector onto the plane that is normal to the camera
direction (i.e., the viewing axis). This simplifies the specification of the
CameraUpVector
property, because it need not lie in this
plane.
In many cases, you might find it convenient to visualize the desired up vector in terms of angles with respect to the axes x, y, and zaxis. You can then use direction cosines to convert from angles to vector components. For a unit vector, the expression simplifies to
where the angles α, β, and γ are specified in degrees.
XComponent = cos(α*(pi/180));
YComponent = cos(β*(pi/180));
ZComponent = cos(γ*(pi/180));
Consult a mathematics book on vector analysis for a more detailed explanation of direction cosines.
Calculating a Camera Up Vector
To specify an up vector that makes an angle of 30° with the zaxis and lies in the yz plane, use the expression
upvec =
[cos(90*(pi/180)),cos(60*(pi/180)),cos(30*(pi/180))];
and then set the CameraUpVector
property.
set(gca,'CameraUpVector',upvec)
Drawing a sphere with this orientation produces