Need help with zoom!

Community Forums/Monkey Talk/Need help with zoom!

SLotman

(Posted 2013) [#1]

I'm trying to zoom where the player clicks on a small part of the screen (a 600x600 area) - but for the life of me, I can't figure it out how to do it properly!

Not only it needs to zoom in around where the player clicks, but it shouldn't show "black borders", so the visible area shouldn't scroll outside it's dimensions.

Here's what I have:

Import autofit
Import mojo

Class color
   Field R:Int, G:Int, B:Int
End Class

Class zoomTest Extends App
   Field colors:color[100]      ' just to hold all colors on screen
   Field zoomX:Float, zoomY:Float ' position where you clicked on screen
   Field curZoom:Float            ' current zoom level
   Field zoomEnabled:Bool         ' are we zooming in?
   
   Method OnRender()
      UpdateVirtualDisplay()      

      Cls
      
      PushMatrix() 
      
      If zoomEnabled Then
         ' update zoom
         If (curZoom<1.499) Then
            curZoom = curZoom + (1.5-curZoom) * 0.10
         Else 
             curZoom = 1.5
         End If

         Local centerX:Float = zoomX*curZoom
         Local centerY:Float = zoomY*curZoom
         
         Local posX:Float = 300-centerX
         Local posY:Float = 300-centerY
         
         If posX>0 Then posX=0
         If posY>0 Then posY=0
         
         Local diff:Float = (600*curZoom)-600
         If posX<-diff Then posX=-diff
         If posY<-diff Then posY=-diff

         Translate posX, posY
         Scale curZoom, curZoom
      End If

      ' draw grid
      For Local y:Int = 0 Until 10
      For Local x:Int = 0 Until 10
         SetColor colors[x+y*10].R, colors[x+y*10].G, colors[x+y*10].B
         DrawRect x*64, y*64, 63, 63
      Next
      Next
      SetColor 255,255,255
      DrawText "play area", 10,10

      ' restore the matrix, so it's possible to draw the right-fixed panel      
      PopMatrix()
      Scale 1,1
      Translate 0,0
      
      ' draw "fixed" panel
      SetColor 255,0,0
      DrawRect 600,0,200,600
      SetColor 255,255,255
      DrawText "Fixed area", 600,10
   End Method
   
   Method OnUpdate()
       If MouseHit(MOUSE_LEFT) 
          If zoomEnabled=False Then
	        zoomX = VMouseX()
	        zoomY = VMouseY()
	        curZoom = 1
	        zoomEnabled = True
          Else
            zoomEnabled = False
          End If
       End If
       
   End Method
   
   Method OnCreate()
      SetUpdateRate 60
      SetVirtualDisplay 800,600
      
      colors = New color[10*10]
      For Local f:Int=0 Until 10*10
         colors[f] = New color()
         colors[f].R = Rnd(255)
         colors[f].G = Rnd(255)
         colors[f].B = Rnd(255)
      Next
      
      zoomEnabled = False
      curZoom = 1
   End Method
End Class

Function Main()
   New zoomTest()
End Function

If you click on the upper-left corner, the zoom behaves as expected. Anywhere else, it "jumps" around and behaves erratically.

I'm 2 days trying to figure this out, without success... can anyone help me out?

Edit: Changed the code a bit - it's almost working now, just some squares that have some strange movement when zooming in...

Last edited 2013

shinkiro1

(Posted 2013) [#2]

Just a tip: You use Scale 1, 1 and Translate 0, 0 after you have popped the matrix which is not necessary. PopMatrix() will reset all Scale, Translate and Rotate commands to the state where it was when you called PushMatrix().