Tag Archives: Compositing

Faking Reflections on set.

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It’s all smoke and mirrors.

This came up recently because there was no glass in the window of the set. All the reflections were to be added in post from photos…. but when the actor stood at the window the Director wanted to see his reflection.

This is a simple trick for a locked off shot. The action is filmed with two cameras one for the main image and a 2nd camera for the refection.

You can find the position of the main camera simply by reflecting the main cameras position in the mirror plain.

  • Both cameras are equidistant from the mirror and targeted at the same point on the mirror plain.
  • A line connecting the nodal point ( focal center ) of each camera is perpendicular to the mirror ( at 90° )
  • both cameras should have the same FOV.

 

Fake_reflections

Outline of our linear workflow

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This is the outline of our linear workflow. It works for both Fusion and Nuke.Viewing Linear workflows

The Composite

Setting up our linear workflow is relatively straight forward.

The key points are:-

  1. Inputs and outputs are 10 bit dpx files.
  2. the log to linear operation should match the camera profile ( Cineon, s-Log, Arri log c, etc )
  3. the log to linear operation on the input is inverted for the linear to log operation on the output.
  4. Composite with a floating point colour depth.

The Display

There are two methods for viewing the composite.

  1. No LUT file.  Without a grading LUT the only option is to apply a simple gamma to view the composite.
  2. LUT files. If a Colourist is involved then the linear image MUST be converted to a log plate before the LUT file is applied.

Further reading

  1. Simple Log to Lin workflow in Fusion
  2. Using Stacked LUTs in Fusion

Tips for creating stereoscopic 3D ( S3D )

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If people were meant to see 3D movies they would have been born with two eyes.
-Apocryphally attributed to Sam Goldwyn

Stereoscopic 3D is here to stay. Studios and manufacturers are pushing more shows and fancier tech. While digital workflows, impossible in the early days, mean a better experience for the viewer without the headaches of poorly balanced S3D.

This is an outline of our workflow for a native S3D show. At Lexhag the depth grade is done on the fabulous Mistika. For VFX I’ve invested in Eyeon Dimension.

Continue reading →

Scripting Tip: Useful equation to blend between two values.

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This is a simple but very useful equation to blend between two values A and B.

( A * w ) + ( B * ( 1 – w ) )

w is a weight value.

Blend maths for compositing and rigging

When w = 0 the answer is B,
and when w = 1 the answer is A.

( A * 0 ) + ( B * ( 1 – 0 ) ) = A
( A * 1 ) + ( B * ( 1 – 1 ) ) = B

This equation is used all over computer graphics. It the basis of compositing pixels, and can be used to make controls for technical animation ( see this eye rig setup for 3dsMax )

Tutorial: Using the maths as an expression in Eyeon fusion.

In this tutorial I use an expression script to animate a blend between two changing positions. This allows the creation of a new point based on the current position of two other points.

You can download a sample file here

 

Note: using *  in algebra …

The convention is write equations concisely without the * for multiplication like this:

A w  + B ( 1 – w )

This is because hand written algebra tends to use single letters for variables, and multiplication signs can get confused with the variable x. While this form is easier to read, it can be confusing were people are  used to reading computer code, and are expecting * for multiplication and long variable names.