46 lines
2.1 KiB
Python
46 lines
2.1 KiB
Python
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"""Schema 8: a node has a pivot.
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`[:xform :pivot]` is back in the transform, as the point rotation and scale are
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composed about: `local = T(pos)·T(piv)·R·K·S·T(-piv)`. Schema 7 deleted it, on
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the argument that an anchor is a peg — true as algebra, and not true as a feature.
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A peg is a node, and a turn about a point that is not the turning node's own
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origin still has to solve for a position to hold that point still; that solution
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is an arc in the angle while a position channel tweens along the chord, so it is
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right on the frame it is written and wrong on every frame between two keys. A
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drawing escaped it, since its origin is the middle of what it draws. A symbol
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instance could not: its origin is its symbol's, which is the top-left corner of
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the stage, so one keyed turn of an instance swung its drawing round that corner
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on an orbit the size of the stage.
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CONVERTED, unlike 6 and 7, because adding this one is exact. A schema-7 node has
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no pivot; an absent pivot reads as [0 0]; and T(pos)·T(0)·M·T(-0) is T(pos)·M to
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the last bit of the mantissa. Every stored document therefore composes to exactly
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the matrices it composed to before, dense tier-2 transforms included, so there is
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nothing to guess at and no node a conversion could silently move. The version is
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restamped and nothing else is touched.
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What a converted document does NOT get is a pivot somebody chose: nodes placed
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before this carry none, so they still turn about their own origin until the first
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turn or scale writes one — `gesture/with-pivot`, from the middle of what the node
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draws at that moment — or until the cross is dragged (ctrl/cmd-drag on the stage).
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"""
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from django.db import migrations, models
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def forwards(apps, schema_editor):
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apps.get_model("clips", "Project").objects.update(schema_version=8)
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class Migration(migrations.Migration):
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dependencies = [("clips", "0016_an_anchor_is_a_peg")]
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operations = [
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migrations.AlterField(
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model_name="project",
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name="schema_version",
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field=models.PositiveIntegerField(default=8),
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),
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migrations.RunPython(forwards, migrations.RunPython.noop),
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]
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