Rotating GUI issues, issues with X,Y cords.

Hi Graeme, I think I understand what's going on...

Your function 'setMapLocation' actually calculates the screen-space pivot point ('mapCenter') for the rotating gui element.

So 'mapCenter' is actually the position you want to pass to GUIUtility.RotateAroundPivot. If you did that, then the parameters you're currently passing to 'GUI.DrawTexture' would make the texture rotate around its centre.

But you want to rotate the texture around a point other than its centre. So you just have to shift the coords passed 'GUI.DrawTexture', to offset them by (textureCentre-texturePivot).

If you also want to scale the rotating texture, you would scale that offset as well as the dimensions passed to 'GUI.DrawTexture'.

You might want to call 'setMapLocation' every frame instead of just on startup, so that the gui positions & sizes update correctly if the window is resized or the resolution is changed.

Here's a modified version of the script that does what I think you want it to do. Let me know if I've misunderstood or if you have any questions :)

 public var testTexture: Texture2D = null;

 var centerObject : Transform;

 enum sweepLocationValues {topLeft, topCentre, topRight, middleLeft, middleCentre, middleRight, bottomLeft, bottomCentre, bottomRight, custom}
 var sweepLocation : sweepLocationValues = sweepLocationValues.middleCentre;

 var screenSpacePivotCustom : Vector2 = Vector2(0,0);

 // size of the radar background as a percentage of the screen width
 private var backgroundSizePercent = 20;

 // size of the radar overlay relative to the size of the radar background
 private var overlaySizeFactor = 0.4;

 // dimensions of the radar background
 private var backgroundDimensions : Vector2;

 // dimensions of the rotating radar overlay
 private var overlayDimensions : Vector2;

 // offset from the top-left of the overlay texture to the pivot of its needle
 private var overlayLocalPivotOffsetFromTopLeft = Vector2(1/8.0, 1/8.0);// eg. needle pivot is at (16,16) on a 128x128 texture

 // screen-space pivot for the rotating overlay
 private var screenSpacePivot : Vector2;
 
 function Start () {
     UpdateDimensionsAndCoords();   
 }

 function OnGUI(){

 // Update the dimensions and pivot coords every frame, to account for changes in window size while running
 UpdateDimensionsAndCoords();

 //Here comes the tachoneedle rotation
 var matrixBackup:Matrix4x4  = GUI.matrix;
 var thisAngle:float = Time.frameCount * 2;
 
 var pivot:Vector2 = screenSpacePivot;

 GUIUtility.RotateAroundPivot(thisAngle, screenSpacePivot);

 var needleOffsetFromTopLeft = Vector2(overlayDimensions.x * overlayLocalPivotOffsetFromTopLeft.x,
                                                         overlayDimensions.y * overlayLocalPivotOffsetFromTopLeft.y);

 GUI.DrawTexture(Rect(screenSpacePivot.x-needleOffsetFromTopLeft.x,screenSpacePivot.y-needleOffsetFromTopLeft.y,overlayDimensions.x,overlayDimensions.y),testTexture);

 GUI.matrix = matrixBackup; 
 }
 
 // Update the gui dimensions and the screen-space pivot for the rotating radar overlay
 function UpdateDimensionsAndCoords() {

     backgroundDimensions.x = Screen.width*backgroundSizePercent/100.0;
     backgroundDimensions.y = backgroundDimensions.x;

     overlayDimensions = backgroundDimensions * overlaySizeFactor;

     //sets screenSpacePivot based on enum selection
     if(sweepLocation == sweepLocationValues.topLeft){
         screenSpacePivot = Vector2(backgroundDimensions.x/2, backgroundDimensions.y/2);
     } else if(sweepLocation == sweepLocationValues.topCentre){
         screenSpacePivot = Vector2(Screen.width/2, backgroundDimensions.y/2);
     } else if(sweepLocation == sweepLocationValues.topRight){
         screenSpacePivot = Vector2(Screen.width-backgroundDimensions.x/2, backgroundDimensions.y/2);
     } else if(sweepLocation == sweepLocationValues.middleLeft){
         screenSpacePivot = Vector2(backgroundDimensions.x/2, Screen.height/2);
     } else if(sweepLocation == sweepLocationValues.middleCentre){
         screenSpacePivot = Vector2(Screen.width/2, Screen.height/2);
     } else if(sweepLocation == sweepLocationValues.middleRight){
         screenSpacePivot = Vector2(Screen.width-backgroundDimensions.x/2, Screen.height/2);
     } else if(sweepLocation == sweepLocationValues.bottomLeft){
         screenSpacePivot = Vector2(backgroundDimensions.x/2, Screen.height - backgroundDimensions.y/2);
     } else if(sweepLocation == sweepLocationValues.bottomCentre){
         screenSpacePivot = Vector2(Screen.width/2, Screen.height - backgroundDimensions.y/2);
     } else if(sweepLocation == sweepLocationValues.bottomRight){
         screenSpacePivot = Vector2(Screen.width-backgroundDimensions.x/2, Screen.height - backgroundDimensions.y/2);
     } else if(sweepLocation == sweepLocationValues.custom){
         screenSpacePivot = screenSpacePivotCustom;
     }
 }