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Tuesday, 31 January 2012

The Definition of Wedging in FX

I came across a term that I havent been using for 2 months. Its called "wedge".

I don't know if its a proper industry term for FX artists, but at dneg London all the leads and artists working on costume use it. I've tried to look-up the term on the internet, but I havent been able to find it in an article that mentions it in a vfx context.

To wedge some values is to set off a few simulations with a range of value,(hopefully derived from some kind of educated guess).

At the end of the processing, the FX artist comes back and takes a look at the result and use the value that gave the result closest to his/her satisfaction.

I am wondering why it is called wedging. It is probably due to the fact that the artist is trying to squeeze in a few simulations instead getting the computer to just process 1 set of values. This is true especially in a big facility where you have a huge number of processors. To send off a few sim jobs simultaneously would definitely be much more efficient than sending off 1 job, waiting for the result, and then setting off another job with another set of refined values.

This would apply to rendering as well, where the Lighting artist would set off different renders with different values or light placements, and see which of the returned results are more favourable.


  1. The term comes from photography, where transmission density of different glass was once measured through a strip of glass with progressively more opacity (simulating a wedge-shaped chunk of glass.) You would sample values through the "wedge" to get a range of results.

    The use then became more general, where a "wedge" of photographs would refer to a number of prints of different exposures, and later any collection of variants of an image used to select the best values of any given parameter.

    Today in CGI, we create "wedges" to explore the visual impact of changing any parameter, to determine the best compromise between look and rendering speed for example, or any other useful visual comparisons.

    Another fun term that's a holdover from photography is referring to a collection of reference images as a "morgue."

    Nice blog, cheers.

  2. Hey Andy,

    Cheers for visiting my blog!

    That is indeed a really a great insight into the origin and the process! You must really have been in this industry for a long time to know things like that.

    I will definitely read more into the wedging process you've just mentioned, and the "morgue" too! ;)

    Thanks again!