Real Camera and Virtual Camera

Because Previzion uses actual measurements and knows where the real camera is in physical space, we need remember that we are dealing with two coordinate systems that are aligned with one another.  In other words, the virtual camera and the physical camera align to each other based on the positioning information Previzion’s sensors feed.  Just like satellites allows your GPS to know where it is, fiducial targets (in the case of the Intersense) lets Previzion know where it is.

In Previzion, the panels to look at in the tracking tab are:

  • Camera
  • Camera Offsets

When Camera Offset is all reset to zeros, meaning with no offsets, the figures displayed in the Camera panel are actual dimensions of where the physical camera is based on sensor information.  In the image above, Position y (cm) shows 156.00.  This mean the camera is actually 156.00 cm off the ground.

Positioning the Virtual Camera

The camera position tab shows a real time update of the current camera position.  When the Video input is Enabled, the update frequency is lowered, to lower the system overhead, updating every second or so.

To edit the virtual camera position directly, click the Edit button, in the Camera panel. The light next to it will go red, to indicate that the virtual camera is not being controlled directly by live tracking data. With the video signal enabled, the Camera position will still refresh at a slower rate, but Camera Offset will update at a faster rate while things moves about.

Like other settings in Previzion, the small opposing arrows to the left of the input box serve as sliders and work by clicking and dragging up and down to change the value in the corresponding box.  You may also type in a given value into each box.

  • Position X (cm) – translates front and back axis or  northing
  • Position Y (cm) – translates up and down axis or elevation
  • Position Z (cm) – translates side to side axis or easting
  • Pan (deg) – rotates side to side
  • Tilt (deg) – rotates up and down (not editable)
  • Roll (deg) – “dutch-angles” around x-axis (not editable)

Hold down Control while clicking and dragging for fine grained control, or scroll with the mouse wheel for high speed motion.

Un-click Edit to commit to your changes.


Free Form Camera Motion

For a more “Maya-like” position editing, you may mouse over the Viewer Window that is now marked by yellow corners.  Use the same mouse gestures that Observer View uses:

  • Scroll up/down – camera moves forward and back
  • Alt + center-click drag – moves side to side (holding shift speeds up this movement)
  • Alt + right-click drag – moves forward and back fluidly (holding shift speeds up this movement)
  • Alt + left-click drag – translates around the geometry/object the yellow center cross is pointing to
  • Shift + Alt + left-click drag – pans/tilts the camera from its nodal position

When editing these values, you will notice Camera Offset panel values changing to accommodate the changes.

Make sure to un-click Edit to commit to your changes.  Any offset Tilt and Roll will revert back to match the physical camera’s Tilt and Roll.