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Spinal Solve Mode
In Solve mode, you are changing the solve itself, generally by adding constraints on the camera path, then re-solving. The RMS error will always get worse! But it lets you interactively repair weak spots in your solve.
The spinal solve performs a Refine operation on your existing solution, meaning that it makes small changes to that solution. If the constraints you add after the initial solve, either directly or by dragging with the spinal solve mode, change the solution too much, then you will get a solution that is “the best solution near the old solution” rather than the best overall solution, which you would obtain by starting the solve from scratch (ie Automatic solving mode).
To maintain interactive response rates, the spinal solve panel allows you to terminate the refine operation early—and while dragging you’re just going to be changing things again anyway. When you stop dragging, SynthEyes will perform a last refine cycle to allow the refine to complete, although you can also keep it from taking too long. After you’ve been moving around for a bit, especially if your solves are not completing all the way, you can click the Finish button to launch a final normal Refine cycle (Finish is the same as the Go button on the solver panel).
Spinal editing might be used in especially subtle ways on long shots. Match- moving inherently produces local “rate of change” measurements, and small random errors (often amplified by small systematic effects such as lens distortion or off-center optic axis) accumulate to produce small twists in the geometry by the end of a long traveling shot. If you have GPS or survey data you can easily fix this using a few locks. But survey data is not always available.
These accumulating errors can be particularly problematic when a long shot loops back onto itself. Suppose a shot starts with a building site for a house, showing the ground where it will be. The shot flies past the house, loops around, then approaches from the side. However, the side view does not include the ground, but only some other details not visible from the front. The inserted house is now seen at an incorrect location, perhaps slanted a bit. The path needs to be bent into shape, and spinal path editing can help you achieve that.
Please keep in mind that the results of these manipulated solves are generally not the same result you would obtain if you started the solve again from scratch in Automatic solving mode. You might consider re-starting the solve periodically to make sure you’re not doing a whole lot of work on a marginal solution.
Using soft locks and spinal editing mode is a black art made available to those who wish to use it, for whatever results can be obtained with it. It is a tool that affects the solver in a certain way. There is no guarantee that it will do the specific thing that you want at this moment. If it does not do what you think it “should be doing,” it is not a bug.
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