How to translate a primitive along the y-axis of the primitive's model matrix

CesiumJS
1

1. A concise explanation of the problem you're experiencing.

I have a polylineGeometry primitive centered on 3D entity and I want to translate the geometry along the y-axis of the model matrix of the polylineGeometry primitive. So think of shifting a box outline from the center on the entity to one of the edges on the entity.

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.

This is the model matrix of the polylineGeometry and I can show the debugAxes on this geometry. I want to translate the geometry along the y-axis of the model matrix, which is the green axis of the debugAxes.

where
    const modelMatrix = Matrix4.multiplyByMatrix3(
      Transforms.eastNorthUpToFixedFrame(
        Cartesian3.fromDegrees(longitude, latitude, altitude)
      ),
      new Matrix3.fromQuaternion(
        new Quaternion.fromHeadingPitchRoll(
          new HeadingPitchRoll(
            orientation.headingRadians,
            orientation.pitchRadians,
            orientation.rollRadians
          )
        )
      ),
      new Matrix4()
    );

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

There is a geometry drawn around an entity at lat, lon, alt, with heading, pitch, roll orientation and I want to translate the polylineGeometry along the y-axis of the model matrix.

4. The Cesium version you're using, your operating system and browser.
  "cesium": "1.48.0", windows 10, Version 74.0.3729.131 (Official Build) (64-bit)

2

This might be easier to visualize if you have a small Sandcastle (https://cesiumjs.org/Cesium/Build/Apps/Sandcastle/) example - but it looks like you should be able to apply an offset as you describe there, using Transforms.eastNorthUpToFixedFrame. Does that not work?

It would be helpful to show what you currently have, and what you’re trying to get instead.