48 wiersze
1.5 KiB
TypeScript
48 wiersze
1.5 KiB
TypeScript
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import { Point } from "../vendor/bezier-js";
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import { normalizedPoint2rad, scalePointXY, subtractPoints } from "./point";
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import { PointWithNormal } from "./specs";
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import { rad2deg } from "./util";
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function normalizeDeg(deg: number): number {
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deg = deg % 360;
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if (deg < 0) {
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deg = 360 + deg;
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}
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return deg;
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}
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/**
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* Convert the given normal in screen-space coordinates into
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* degrees of rotation in attachment-space coordinates.
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*/
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export function normalToAttachmentSpaceDegrees(normal: Point): number {
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// We need to flip our y because we're in screen space, yet our
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// rotational math assumes we're not.
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const yFlipped = scalePointXY(normal, 1, -1);
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const rad = normalizedPoint2rad(yFlipped);
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// The origin of our rotation space assumes that "up" is 0
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// degrees, while our rotational math assumes 0 degrees is "right".
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const reoriented = normalizeDeg(90 - rad2deg(rad));
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return reoriented;
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}
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/**
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* Given a child point that needs to be attached to a parent
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* point, return the amount of translation and rotation we
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* need to apply to the child point in order to align its
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* position and normal with that of its parent.
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*/
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export function getAttachmentTransforms(
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parent: PointWithNormal,
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child: PointWithNormal
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) {
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const translation = subtractPoints(parent.point, child.point);
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const parentRot = normalToAttachmentSpaceDegrees(parent.normal);
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const childRot = normalToAttachmentSpaceDegrees(child.normal);
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const rotation = parentRot - childRot;
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return { translation, rotation };
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}
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