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Adjust the World Size on the solver panel to a value comparable to the overall size of the 3-D set being tracked, including the position of the camera. The exact value isn’t important. If you are shooting in a room 20’ across, with trackers widely dispersed in it, use 20’. But if you are only shooting items on a desktop from a few feet away, you might drop down to 10’.
Important : the world size does not control the size of the scene, that is the job of the coordinate system setup.
Tip : SynthEyes will automatically adjust the world size if it is determined to be necessary. Adjust the Perspective View's clipping plane and other settings to desired values, if necessary, using right-click/View/Perspective View Settings.
Advanced . You can disable SynthEyes’s automatic world size update from the Advanced Solver Control panel. Do this only with good cause, eg for marginal solves; use Edit/Scene Settings to change those.
There is a checkbox between the text "World Size" and the spinner itself. When the checkbox is checked, adjusting the spinner sets the world size for all objects; when it is off, the spinner affects only the current tracker host object. The checkbox is checked by default as that is most common and useful. When the world sizes are not all the same, the spinner value is underlined in red, ie marked as a key, for information. (The world size cannot be animated.)
Get Your Inner Geek On: SynthEyes divides all coordinate values by the world size internally as it works. With the default world size of 100, a coordinate value of 64 will be internally processed as 0.64. Why bother? If SynthEyes needs to square the value, 64 becomes 4096, while 0.64 becomes 0.4096. If we need to add one unit, we get either 4097 or 0.4196. The world size can be too big, as well as too small. A world size of 10000 would turn 64 into 0.0064, and squaring that would be a tiny 0.00004096. By normalizing all the values by a reasonable world size, SynthEyes ensures that all the values it is working on stay near 1.0, maintaining the accuracy of its calculations (computers use only approximate arithmetic). And yes, SynthEyes does a LOT of calculations.
Choose your coordinate system to keep the entire scene near the origin, as measured in multiples of the world size. If all your trackers will be 1000 world-sizes from the origin (for example, near [1000000,0,0] with a world size of 1000), accuracy might be affected. The Shift Constraints tool can help move them all if needed.
Note : There are some requirements that the world size must match between cameras on a stereo rig, and between camera and moving objects especially when path locks are present. SynthEyes will enforce these during the solve.
As you see, the world size does not affect the calculation directly at all. Yet a poorly chosen world size can sabotage a solution. If you have a marginal solve, sometimes changing the world size a little can produce a different solution, maybe even the right one.
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