Moving an object relative to the camera

My latest project has a small square map (a flat 3d mesh) that can be rotated. What I would like to do is now be able to allow the user to change the view from side on to top view (and everything inbetween). In theory all I have to do is rotate around the X axis.

This works fine. I hit a problem though when I've rotated the map (rotated around the Y axis). If I've turned the square 45 degrees around Y then try to rotate it around X, I expect to see the corner of the square that's now facing me go straight up and over. Instead it rotates based on the original x axis and not what I'm now looking at (ie, it seems to rotate from right over to left).

Does anyone have any ideas on how to have it rotate how I'd like it to? (ie. relative to how it's now seen from the camera?)

Simple method:

function RotateMapAboutXAxisRelativeToCamera(EntityHandle,AmountToRotateBy#,CameraHandle)

pivot=createpivot()
positionentity pivot,entityx(EntityHandle),entityy(EntityHandle),entityz(EntityHandle)
rotateentity pivot,entitypitch(camerahandle),entityyaw(camerahandle),entityroll(camerahandle)
entityparent EntityHandle,pivot ;set the pivot as the parent of the entity
turnentity pivot,AmountToRotateBy,0,0
freeentity pivot ;free the pivot as no longer need it

end function

then when the user presses a button do something like this:

if keydown(ButtonScanCodeForRotatingForwards)<>0 then RotateMapAboutXAxisRelativeToCamera(MapEntity,1.0,Camera)

if keydown(ButtonScanCodeForRotatingBackwards)<>0 then RotateMapAboutXAxisRelativeToCamera(MapEntity,-1.0,Camera)
 

If, as you suggest, you child the EntityHandle of your entity to the pivot as a parent, when you will free up your pivot, you will also free up the entity that you made a child to the pivot, as per the above descriptionf from the B3D Help.

Thanks guys, I'll give that a go now!!!

Thanks SirGak! That's exactly the problem I just found when trying out the code. I'm going to try changing it to "PointEntity" instead and see if that works.

PointEntity loses the rotation I've put on the object. Any ideas?

Ahhh - figured it out, I don't need to worry about pivots and PointEntity - all I have to do is use turnentity with the "global" parameter set to 1. I would've figured it out earlier if that had been documented - oh well, thanks all for your help!!!!

Oops - you are right Sir Gak, I'd forgotten about that (haven't used blitz3d in a while) - you would also need to set the entityparent back to '0' I guess and include a entityparent EntityHandle,0 statement before freeing the pivot.

Cheers Matty!