G Spring is a transition that "bounces" the incoming clip onto the video over the top of the outgoing clip as if it were attached to a spring. G Spring uses a physics based spring simulation. The majority of the controls for the transition govern the exact nature of the simulation. The transition works in an iterative manner. This means that each time FCP asks what a frame of the transition should look like, the transition calculates the new frame based upon the previously calculated frame. When rendering the transition, FCP asks for all the frames in order, and the transition will work. If you examine the frames of the transition before rendering, you will therefore not see exactly what you're going to get - this is a limitation of FCP and this physics based method of calculating a transition. Fortunately, it renders fast.
Due to the physics simulation, it cannot be pre-determined how long it will take for the bouncing video to settle at the centre of the screen. If the video doesn't settle before the transition ends, it may be necessary to lengthen the transition or speed up the motion of the bouncing video by altering the simulation parameters.
For the transition to work, the incoming image starts off the screen, and is allowed to bounce onto the screen. The Start Wipe Position points to the direction where the incoming image is waiting to begin the transition. To allow the image to bounce in a more interesting fashion, the "Start Wipe Direction" points in the direction the image is moving before the transition begins. The image has an initial velocity governed by "Start Wipe Speed".
Often video clips have borders or edges that don't look good when they're bouncing around the screen. The incoming clip has crop controls so that these edges can be cropped off. The crop controls work similarly to FCPs built in crop controls in the motion panel. If the incoming image is cropped then it may not look good, or it may "pop" when the transition ends. To avoid this situation, the Fade End Image can be used to fade up to the original version of the incoming video near the end of the transition. The Fade At Time controls the percentage through the transition that the original video will begin to fade in.
To enhance the effect, a motion trail can be added to the bouncing video.
Control
Settings
Notes
Start Wipe Position
-360 to 360
The offscreen angular position at which the incoming video starts.
Start Wipe Direction
-360 to 360
The direction the incoming video is moving at the start of the transition.
Start Wipe Speed
0 to 100
The velocity at which the incoming video is moving at the start of the transition.
Mass
0.1 to 10
The mass of the screen - increasing mass will slow the movement of the screen, but also give it greater inertia.
Spring
0 to 1
The spring constant of the simulation - increasing the spring constant will make the spring stronger and springier - decreasing it will make the spring looser and pull less on the screen.
Length
0 to 10
This is the "natural length" of the spring. This can be increased to allow the screen to move around further.
Friction
0 to 1
Friction acts like a viscous force that retards the motion of the screen. A friction of zero will send the screen in to chaos as there will be nothing stopping the spring stretching and the screen moving. Increasing the friction will dampen the movement.
Crop Left
0 to 100
Crops the incoming video from the left side.
Crop Right
0 to 100
Crops the incoming video from the right side.
Crop Top
0 to 100
Crops the incoming video from the top.
Crop Bottom
0 to 100
Crops the incoming video from the bottom.
Motion Trail
on
off
Turns on the motion trail effect on the emotion of the bouncing clip. Note that Motion Trails are not affected by cropping.
Trail Opacity
0 to 100
Sets how solid the trail appears.
Fade End Image
on
off
Fades from outgoing video to original (stationary) incoming video.
Fade at Time
0 to 100
Sets the percentage of the transition at which the original incoming clip should begin to fade in.
