Fix incorrect calculation in get distance for diagonals #78
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mikeparker
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aJamDonut
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Jan 23, 2024
src/easystar.js
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| } else { | ||
| return DIAGONAL_COST * dy + dx; | ||
| return DIAGONAL_COST * dy + (dx=dy); |
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@mikeparker sorry i know its old, i implemented this change myself also but wanted to ask... why was it dx=dy
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Yeah it's pretty old, that looks like a typo to me, it's probably supposed to be (dx-dy)
If I was better with javascript this is exactly the sort of thing a unit test should check for.
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Yes that makes sense thinking about it. If dx < dy then you travel all the X distance via diagonals then the remainer dy via vertical moves.
If its the other way around then you travel all the Y distance via diagonals then the remainder dx via horizontal moves.
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I am implementing the ability to return incomplete paths and noticed this calculation was off.
For example if a node is 1x,1y away from the target this function incorrectly returns a distance of 2.4 instead of 1.4.
Another example, if a node is 4x,2y away, this should move diagonally for 2y which will also result in 2x movement, then the remaining 2x, so it should be
2*DIAGONAL_COST + 2*STRAIGHT_COSTrather than2*DIAGONAL_COST + 4*STRAIGHT_COST