EllipseHitSpritePixels - Learn To Code - PlayBASIC Documentation

EllipseHitSpritePixels

CollisionState = EllipseHitSpritePixels(X, Y, RadiusX, RadiusY, SpriteIndex, Accuracy#)

Parameters:

    X = The X coordinate of the ellipse
    Y = The Y coordinate of the ellipse
    RadiusX = The radius of the ellipse along the X axis
    RadiusY = The radius of the ellipse along the Y axis
    SpriteIndex = The Sprite to check for collision against
    Accuracy# = The level of accuracy that should be used.

Returns:

CollisionState = The result of the collision query (0= No collision ,1 = Collision)

      The EllipseHitSpritePixels function detects if a collision occurs between an Ellipse shape and any pixel within a sprite.

Example Accuracy Values
      0.25 = Reduce collision accuracy to 25%
      0.50 = Reduce collision accuracy to 50%
      0.75 = Reduce collision accuracy to 75%
      1.00 = Set collision accuracy to 100%
      2.00 = Set collision accuracy to 200%

FACTS:

* The Accuracy parameter allows the user to fine tune the quality of the pixel level sprite collisions. Generally speaking the lower the quality the faster the comparison. On the flip side the higher the quality the more accurate, but slower the comparison. It's up to the user to choose an accuracy level that's appropriate for your images and the performance of your game.

* Pixel level collisions ignore the sprites transparent colour.

Mini Tutorial:

This example creates a random image, creates 10 randomly positioned sprites on the screen using this image. The main loop rotates the sprites while scans them for collisions using EllipseHitSpritePixels

; clear the screen to black
  Cls RGB(0,0,0)


; Make an image with circles on it
  MyImage=NewFXImage(100,100)
  RenderToImage MyImage
  For lp =0 To 50
     CircleC Rnd(100),Rnd(100),RndRange(2,10),1,RndRGB()
  Next


; render to screen
  RenderToScreen


; Make 10 sprites
  For spr=1 To 10

   ; postion the spriote randomly on the screen
     x=Rnd(GetScreenWidth())
     y=Rnd(GetScreenHeight())

   ; Create the sprite using image #1
     Spr=NewSprite(x,y,MyImage)

   ; center the sprite
     CenterSpriteHandle spr

  Next



  Do
     Cls RGB(0,0,0)

   ; Check if the mouse  is over a sprite
     mx#=MouseX()
     my#=MouseY()

     RadiusX#=100
     RadiusY#=50

   ; start for/next loop from 1 to 10
     For spr=1 To 10

      ; Turn this sprite
        TurnSprite spr,0.25

      ; Check if our test Ellipse hits any pixels in this sprite
        If EllipseHitSpritePixels(mx#,my#,RadiusX#,RadiusY#,spr,1)=true
         ; if collision flash the sprite
           SpriteDrawMode Spr,2+4096
        Else
         ; Set it's draw mode to just rotated
           SpriteDrawMode Spr,2
        EndIf
     Next

     DrawAllSprites

   ; draw the test point
     EllipseC mx#,my#,RadiusX#,RadiusY#,false,RGB(255,255,255)

     Sync
  Loop


Related Info:	CircleHitSprite \| PointHitSprite \| PointHitSpritePixels \| QuadHitSprite \| RayHitSprite \| RectHitSprite \| ShapeHitSprite \| SpriteCollisionMode \| SpriteHit \| SpritesOverlap :