Quaternion to HeadingPitchRoll

CesiumJS
1

Hi,

I have a entity from CZML datasource. I can get it’s position in Cartesian and orientation in Quaternion.

I have no problem to transform position to lat / lon using “Cesium.Ellipsoid.WGS84.cartesianToCartographic”.

However, I can’t figure out how to translate quaternion to heading/pitch/roll. (respect to an east-north-up axes centered at the entity position)

Anyone could help?

2

There doesnt appear to be a method for either quat or mat3 to convert into euler angles. You could convert into mat3 then do manual inverse trig on first column for yaw/pitch then the second or column for roll

3

Hello,
I begun a pull in order to retrieve heading pitch roll from a quaternion:
https://github.com/AnalyticalGraphicsInc/cesium/pull/2536/files

4

Hi Bob,

Thank you for the HPR to Quaternion. But I still not sure how to further convert the generated HPR(respect to earth-center frame) into an east-north-up frame.

5

one solution

const scratchInvEastNorthUpFrame = new Matrix4();
const scratchInvRotation = new Matrix3();
const scratchInvRotationQ = new Quaternion();
const scratchLocalQuaternion = new Quaternion();
const scratchLocalHpr = new HeadingPitchRoll();

function getLocalHpr(origin, quaternion) {
    const eastNorthUpFrame = Transforms.eastNorthUpToFixedFrame(origin);
    const invEastNorthUpFrame = Matrix4.inverse(eastNorthUpFrame, scratchInvEastNorthUpFrame);

    const invRotation = Matrix4.getRotation(invEastNorthUpFrame, scratchInvRotation);
    const invRotationQ = Quaternion.fromRotationMatrix(invRotation, scratchInvRotationQ);

    const localQuaternion = Quaternion.multiply(invRotationQ, quaternion, scratchLocalQuaternion);
    
    return HeadingPitchRoll.fromQuaternion(localQuaternion, scratchLocalHpr);
}