Visual Effects
Digital Paint
Paint refers to the processes whereby one would manually or proceedurally digitally alter the rgb
pixel values of a frame or range of frames using, what are termed, paint tools.
Applications which do digital paint work are often refered to as paint-boxes. The perennial example
of a digital paint application is Adobe's Photoshop. Though Photoshop is used in film and video
opperations there are other tools such as Quantel's Henry and Domino as well as Puffin's Commotion
which were designed from the ground up to function as paint boxes for film and video.
Standard tools
include a paint brush, clone / stamp, smudge, blur / sharpen, selection, pencil, eraser, dodge / burn,
wire-remover and airbrush. An explanation and example of each tool's use follows:
- Paint Brush: The paint brush tool is used with varying, and often user defined, brushes to
paint solid color values onto each frame of digital footage. An example of its use would be
to paint out a logo on a moving surface with a fairly constant color value.
- Clone / Stamp: These refer to a tool which is capable of painting in the same fashion as the
standard paint brush but instead of a solid color as its source the clone tool will have the
capability of using a different region of the frame as a source for the pixel vlaues it lays
down. Cloning is used in instances where a complex pattern must be replicated in an area of
the frame where it dosent currently exist. The paint box portion of Puffin Design's Commotion
can use a region of a frame with a temporal (time based) offset or even frames from another
piece of digital footage as the source in addition to the standard functionality.
- Smudge: The smudge tool will take existing pixel values and provide the effect of smearing
them in a controlled fashion across the frame as though they were wet paint. Smudging is
sometimes used as a quick and dirty method for removing unwanted specs from plates.
- Blur / Sharpen: These work in the same fashion to produce opposite effects. Usually a
strength value is chosen by the user and areas which are stroked by the user are blurred
or sharpened accordingly. The blur version is great for adding the illusion of heat distortion
from fire or explosions.
- Selection: The selection tool(s) are used to describe an area where paint or filters
are to be applied. Selection tools can have many shapes from the standard rectangular
and ellipsoid marquee to the freeform lasso. A selection might be made to confine the
work being done on a plate to a small area to reduce mistakes and save time.
- Pencil: The pencil is identical in function to the paint brush but is commonly only a
single pixel in brush size and or is not feathered. In the effects world not too many
photo-realistic effects can be created without featering so I have no example for this.
- Eraser: Even the best make mistakes. The eraser may allow the user to paint to "background"
color or even better to paint in the pixel values of the last saved version, another
Commotion feature.
- Doge / Burn: These tools and terms allude to photographic processes whereby an area is
darkened or lightened respectively. Great for enhancing shadows and hot-spots.
- Wire Removal: Only to be found in effects oriented packages these tools would be used
to remove the appeaarances of the wire rigs often used to support actors and models in
effects shots.
- Airbrush: Extremely similar to the paint brush but with the distinction that it allows
digital paint to "build up" not unlike a spray can.
While there are some applications out to blur the line most of these systems opperate in, what is
called, a destructive fashion. The way a destructive paint-box works is by making its user
responsible for "intelligent saving" and ordering of actions. This is due to the fact that while
most paint boxes may store the footage prior to the last stroke or filter which was applied to it
it is prohibitably ram and disk intensive to allow unlimited undo. This is something that we may
see change as storage becomes less expensive. Examples of apllications which preform non-destructive
opperations are Dicreet's Paint and Adobe's After Effects. Though due to speed and other considerations
destructive paint boxes are still the prefered professional solution.
Back to the Visual Effects area.
Feedback is always welcome drop a line to:
mrehrer@csua.berkeley.edu.
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