Opacity and Blink

Both tell the story through visibility: Opacity sets how transparent an object is from the value, and Blink makes it flash.

Both are available on any SVG object, and both have Expressions and Tag modes.

Opacity

Field	Description
Variable	The variable to read
Default Value	The value used when it cannot be read
Value Bit	Self takes the whole value; choosing a bit index reads only that bit out of the word
Minimum Value · Maximum Value	The values the ends of the opacity range correspond to
Threshold	Filled in, it switches to binary mode
Fade (ms)	How long the transition takes. Left blank, the animation’s default speed is used
Instant (no fade)	Ticked, the object snaps to the target opacity

Two separate behaviours

The form does two different jobs with one type, and Threshold is what decides which applies.

Opacity that varies continuously. Threshold is left blank. The value is proportioned between Minimum Value and Maximum Value and the object takes that opacity. It suits showing an intensity or a density by degree.

Show and hide. Threshold is filled in. Minimum/Maximum Value are then ignored: at or above the threshold the object is fully visible, below it the object is hidden. Add Instant and the change happens with no fade — which is the right behaviour where a warning symbol should appear and disappear.

Showing an object on a condition

Do not look for a separate “visibility” type; this is the job Opacity does. Setting Threshold to 1 and ticking Instant binds a boolean variable straight to show/hide behaviour.

Blink

Field	Description
Variable	The variable to read
Default Value	The value used when it cannot be read
Value Bit	The whole value, or a single bit of it
Duration	The blink period

Blink alternates the object between visible and hidden at Duration. Its use is narrow but clear: a condition the operator must not miss and has not yet acknowledged.

Use blinking sparingly

When several objects blink on one screen none of them stands out; blinking is a mark of priority and loses its value as it multiplies. Colour suits a standing condition, blinking a temporary but critical one. Having the blinking stop when the alarm is acknowledged is the usual pattern, and it gives the operator the “seen” feedback.

Which to use

What you want	How
Opacity by degree	Opacity, Threshold blank
Show or hide on a condition	Opacity with Threshold and Instant
To draw attention to an unacknowledged alarm	Blink
To mark a standing condition	Color

Related

• Element Editor — the fields every binding form shares
• Color — showing state through colour