5D.Pixflow

PURPOSE
Produces an effect in which the colors of an image 'flow' out of their pixels in a fluid manner. The colors flow along vectors found at each pixel from the gradients of a control image. The colors mix together as they go. The effect is useful for novel transitions, as well as for creating animating texture maps for use in other software (e.g. planetary atmosphere textures).
The effect is applied to the current frame of the input clip. This is flowed under the influence of a control image (which can animate, if desired) to produce a sequence of output frames.

INPUT CLIPS
FRAME to Flow: an IMAGE to flow. Only the current image in the clip is used when Restart is set to 1.0.
Luminance Control: the gradients, of the clip's luminance, control the direction in which the Foreground IMAGE pixel colors flow at each pixel.
Background Reveal: can be revealed as the Foreground image flows.

HINTS
Pixflow smears ONE image along lines of flow (changes in intensity) in the control image. This effect can only work because of the way it evolves - from itself - over time. Usually an effect is created based solely on the input clip(s) at the given frame. In this case the next output image is created from the previously created output frame. Therefore using Pixflow is a little different.
See the exercises at the end of this section for further help.

RENDER

STYLE
Once Flow control
Flow Once=0: the flow field is calculated once, from the current image in the Control clip and applied to the current image in the first clip (when Restart Pixflow is pressed).
Flow Each=1: the flow field is computed for each frame of the Luminance Control clip and used to flow the Foreground image.

Black Background treatment

Black=0: colour flows off into oblivion and black flows in to fill partially empty edge pixels.

Reveal=1: as colour flows off the background clip is revealed.

Thin Pixel opacity
Thin=0: when color flows out of a pixel, the pixel is left partially (or wholly) empty. The pixel gets less dense, so (if options are selected appropriately) you can see the background through it.
Stretch=1: when color flows out of a pixel, the material in the pixel stretches without the pixel emptying.

Opaque Pixel treatment
Opaque=0: the 'stuff' that colours the pixel and flows out of it can be thought of as reflecting light to give color.
Luminous=1: the 'stuff' that colours the pixel and flows out of it can be thought of as emitting light. As color flows into a pixel, it will get brighter.

Wrap Edge behavoir.
Wrap=0: if color flows off the edge of the image, it flows in again at the opposite edge (think of the image as being wrapped so that the left and right edges are taped together, and similarly, the top and bottom edges).
Black=1: color flows off into oblivion and black flows in to fill partially empty edge pixels.

Fade (Min: 0.0 Max: 100.0 Default: 0.0)
Controls an overall reduction in density of the flowed image. At 100.0 the flowed image would be transparent everywhere, revealing the background image. Use this to ensure all the Foreground image has gone by the desired frame.

SMOOTH
Value (Min: 1.0 Max: 50.0 Default: 5.0)
Specifies how far apart to look on the control image (in pixels) when finding the control image gradients. Small values tend to give spurious gradients due to only having 256 possible luminance levels. Large value may smear the gradients too much, however.

Passes (Min: 0.0 Max: 10.0 Default: 1.0)
How many smoothing (averaging) passes are made on the flow field derived from the control image gradients. Some averaging is recommended, because flow fields are very sensitive to almost insignificant variations in the control image.

MOTION
Rate (Min: 0.0 Max: 5.0 Default: 1.0)
Maximum radius a pixel color can flow to, between output frames.

DIRECTION
Gradients Gradients=0: the direction of movement is from dark to light areas in the control image.
Tangents=1: the direction of movement is at right angles to the gradients. Tangents tend to give swirly flow, while gradients give straighter paths.

Dirrection Vector flow control
Dir=0: all the vectors are the same length; only the field direction changes.
MagDir=1: the length of the vectors is found from the strength of the gradient and is used to control how quickly the fluid flows, as well as the direction it flows in.

ForwardFlow direction
Forward=0: the motion follows the natural direction of the flow field vectors.
Backward=0: reverses the directions of the flow field vectors after they have been found.

SWIRL
Density (Min: 0.0 Max: 100.0 Default: 0.0)
Number of bumps across the frame width in a turbulence field, which can optionally be added to the flow field (derived from the control field) to add further interest. This must be greater than zero to apply any turbulence.

Amplitude (Min: 0.0 Max: 100.0 Default: 1.0)
Controls the strength of the bumps in the turbulence. The sum of the turbulence (if any) and image gradient-derived flow fields, is normalised then scaled to the flow rate. Making this control large will make turbulence entirely dominate the flow field.

RESTART
Restart(Default: 0.0)
Continue=0: the flow continues to evolve using the previously rendered frame as the strarting point.
Restart=1: initialise the state with the Foreground image not having flowed anywhere yet. You will need to restart the flow after making any adjustments and process a few frames to see the result of any changes.

EXERCISES

Exercise 1 - the Restart control

load Pixflow.
load the first input clip - the image you want to flow.
load the second clip to control the direction of the flow (you can use the same image).
- you do not need a third clip for this exercise
- only the FIRST image in the first input clip will be used (the one directly below the first frame of the Pixflow ).
- the control clip can either be a single frame or the sequence.
open the monitor.
move the monitor left and right. Whichever direction you go in the image still flows in the same direction.
check out the animation for Restart. Frame 0 = 1.0 ( restart) and frame 2.0+++ = 0.0 to continue the animation.
- if you change any of the values ( except for Render Style Black ) you should go back to frame 0 to restart the effect.
- when you render the output clip you do not have to set Restart to 1.0 for the first frame. A new sequence is automatically initiated for you.
- a Restart happens automatically when you change resolutions whatever frame you are on.

Exercise 2 - a Flow mix

load Pixflow - load clip to flow - load control clip.
set Motion Direction Gradient to 0.0
set Render Fade to go from 0 to 100.0 over the last 25% of the sequence.
set Render Style Black to 0.0
select Pixflow and duplicate the effect (middle button drag, copy & paste etc).
load a new clip to flow, but use the same control clip.
in the second Pixflow set Motion Direction Forward to 1.0 to reverse the direction of the flow.
render both clips.
use the results with Add or Composite, Flipping one of the sequences so the first sequence flows out revealing the second sequence flowing in.

You cannot use the group feature and process in one pass with this effect as the Flip has no effect. Remember - the flow is created from itself evolving over time.

Control Notes:

if you want to use a moving control clip (2) then set Render Style Once to 1.0. Each generated frame will then use the current frame from the clip. Otherwise only the first frame from this clip is used throughout.
to ensure the image completely disappears - flows completely into itself - you have to cheat a little and use the Render Fade control. At 0.0 the flowed image is at full intensity; at 100.0 this image will be completely tranparent, revealing the background.
use Motion Rate to slow down or speed up the amount of flow per frame.

Note: the final effect will be different at full resolution but working at low resolution will give you a good idea what is happening quite quickly.

There is no Plug In options even though the Time Editor View Plug In appears to be active.

5D.Pixflow

Index