Modifying absolute vs relative rotation

Scripting Issues
1

I’m trying to modify the mouse-modes demo so that the mouse rotates the box in a more intuitive manner.

Currently, moving the mouse rotates the box along it’s own heading and pitch, however I would like the mouse to rotate things along a global heading and pitch. Pretty much, moving the mouse up will always rotate the box upwards relative to the camera. Illustrative picture attached.

I mainly need help figuring out how to turn a delta in screen X and Y to the modified HPR values. The original code is :

self.rotateX += dx * 10 * self.mouseMagnitude
self.rotateY += dy * 10 * self.mouseMagnitude
self.model.setH(self.rotateX)
self.model.setP(self.rotateY)

Which I know I have to modify something to adjust for all three rotation angles. I’ve taken out a global rotation like this, but have no idea how to get the desired result:

hpr = self.model.getHpr()
self.model.setHpr(hpr[0] + dx*10*self.mouseMagnitude, hpr[1] + dy*10*self.mouseMagnitude, 0)

Any help with either translating to a correct dh,dp,dr, or using a panda API function would be great

rotation.png760×410 140 KB

2

To get the desired result, you can use quaternions.
The old model quaternion is multiplied by the quaternion representing the angle deltas, resulting in the new model quaternion:

...

        # rotate box by delta
        deltaHeading = dx * 10 * self.mouseMagnitude
        deltaPitch = -dy * 10 * self.mouseMagnitude
        deltaHpr = (deltaHeading, deltaPitch, 0.)

        # create quaternion representing delta values
        deltaQuat = Quat()
        deltaQuat.setHpr(deltaHpr)

        oldQuat = self.model.getQuat()
        newQuat = oldQuat * deltaQuat
        self.model.setQuat(newQuat)

        self.positionText.setText("Model rotation: {0}, {1}".format(
             int(self.model.getH()*1000)/1000., int(self.model.getP()*1000)/1000.))
        
        return Task.cont

app = App()
app.run()

Hope this helps.

3

That’s exactly what I was looking for, thanks!

I missed the -ve on dy the first time around, which is rather important for ensuring the X and Y coordinates behave in the same way.