mirror of https://github.com/vector-im/riot-web
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@ -14,6 +14,8 @@ See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import { clamp } from "lodash";
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/**
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* This method linearly interpolates between two points (start, end). This is
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* most commonly used to find a point some fraction of the way along a line
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@ -25,5 +27,6 @@ limitations under the License.
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* @returns
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*/
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export function lerp(start: number, end: number, amt: number) {
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amt = clamp(amt, 0, 1);
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return (1 - amt) * start + amt * end;
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}
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@ -0,0 +1,35 @@
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/*
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Copyright 2021 Šimon Brandner <simon.bra.ag@gmail.com>
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import { lerp } from "../../src/utils/AnimationUtils";
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describe("lerp", () => {
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it("correctly interpolates", () => {
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expect(lerp(0, 100, 0.5)).toBe(50);
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expect(lerp(50, 100, 0.5)).toBe(75);
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expect(lerp(0, 1, 0.1)).toBe(0.1);
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});
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it("clamps the interpolant", () => {
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expect(lerp(0, 100, 50)).toBe(100);
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expect(lerp(0, 100, -50)).toBe(0);
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});
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it("handles negative numbers", () => {
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expect(lerp(-100, 0, 0.5)).toBe(-50);
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expect(lerp(100, -100, 0.5)).toBe(0);
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});
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});
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