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Polyline problem calculating s in long distance #12439

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mickae1 opened this issue Jan 17, 2025 · 4 comments
Open

Polyline problem calculating s in long distance #12439

mickae1 opened this issue Jan 17, 2025 · 4 comments

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@mickae1
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mickae1 commented Jan 17, 2025

What happened?

When you create a long polyline, the st.s at 0.5 is not the middle, you can see the example in the sandcastle

Reproduction steps

  1. create a long polyline
  2. make it change color in the middle
  3. you will see that it's not the middle

Sandcastle example

https://sandcastle.cesium.com/#c=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

Environment

Browser:
CesiumJS Version:
Operating System:

@Fav
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Fav commented Feb 14, 2025

When building a polyline, the shortest length of the line segment is calculated, and then the length of each segment is equal to how many minimum lengths n*a (Math.ceil) are calculated, and the s value of each vertex is determined

For example, if there are 3 points (two segments), the first segment is a and the second segment is 1.5a (Math.ceil(1.5) = 2), then the first point has an s value of 0, and the second point has an s value of 0.333, and when rendering, s=0.5, the rendered red-green dividing point position should be to the right of the midpoint, not the midpoint. You can draw it on paper and you'll understand.

According to the debugging results of the example, there are 76 points in the example, and the shortest length is 88, and according to the length distribution result, when s=0.5, the red-green dividing point is not in the center of the segment

@mickae1
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mickae1 commented Feb 14, 2025

ok, but this is troublesome if you want to use the info st.s to draw arrows with the same size :

Image

the sandcastle :

https://sandcastle.cesium.com/#c=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

@Fav
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Fav commented Feb 17, 2025

var polyline = new Cesium.PolylineGeometry({
  positions: Cesium.Cartesian3.fromDegreesArrayHeights(pts),
  width: 10.0,
  granularity:1e-5,  // add
  vertexFormat: Cesium.PolylineMaterialAppearance.VERTEX_FORMAT,
});

....

 // arrow :
 float baseOnS = st.s < 0.5 ? 0.25 : 0.75 ;

Image

@Fav
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Fav commented Feb 17, 2025

link

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