Line Intersect Circle (Ray intersection)

[kevin]

In previous versions of PlayBASIC prior to PlayBASIC V1.083 (beta at this point) the LineIntersectCircle function would produce some rather odd results.  Anyway while fixing that, i've also expanded it to solve the number of intersections the ray has with the circle.

You can customize the type of intersection you want too.   Currently it can either return then First intersection point, or both (if two exist)  as well as selectively returning the normals at the point of intersection.

it's important to note the it only returns the intersection point.  So the ray has to hit the circle. IF the ray is totally inside the circle, then no impact will register.

PlayBASIC Code: [Select]

ScreenWidth=GetScreenWidth()
ScreenHeight=GetScreenHeight()

` =================================
` Create A screen full of Ranodom Circles
` =================================

 Max_of_Circles=100

 Dim Max_numb_of_wall_Segments(1)
 Max_numb_of_wall_Segments(1)=Max_of_Circles
 
 Dim Circles_Xpos#(Max_of_Circles)
 Dim Circles_Ypos#(Max_of_Circles)
 Dim Circles_Radius#(Max_of_Circles)

 For lp =0 To Max_of_Circles
; Set this circles X position
   Circles_Xpos#(lp)  =Rnd(ScreenWidth)
; Set this circles Y position
   Circles_Ypos#(lp)  =Rnd(ScreenHeight)
  ; Set this circles Radius
   Circles_Radius#(lp)   =RndRange(20,30)
 Next lp


` --------------------------------------
` Create the  Players Variables
` --------------------------------------

 PlayerDir#  =90
 PlayerX#  =500
 PlayerY#  =200
 PlayerRadius#   =20
 PlayerSpeed   =5


Do
  Cls 0
  Text 0,0,FPS()

  ` --------------------------------------
  `  Handle the PLayers/Object Movement
  ` --------------------------------------

  move#=0
  If UpKey() Then move#=playerspeed
  If DownKey() Then move#=-playerspeed
  If LeftKey() Then playerdir#=WrapAngle(playerdir#,-3)
  If RightKey() Then playerdir#=WrapAngle(playerdir#,3)

  If move#<>0
   ` Clip PLayers position to screen limits
    If playerx#<0 Then playerx#=screenwidth
    If playerx#>screenwidth Then playerx#=0
    If playery#<0 Then playery#=screenHeight
    If playery#>screenheight Then playery#=0
    playerx#=playerx#+CosRadius(playerdir#,move#)
    playery#=playery#+SinRadius(playerdir#,move#)
  EndIf


  ` --------------------------------------
  `  Render the Player/Object
  ` --------------------------------------

  LockBuffer
   CircleC playerx#,playerY#,playerRadius#,0,$ffffff
   
   playerx2#=CosNewValue(PLayerx#,playerdir#,200)
   playery2#=SinNewValue(PLayery#,playerdir#,200)
   LineC playerx#,playery#,playerx2#,playery2#,RGB(255,0,0)

  ` -----------------------------------------------------
  `  Render Lines and Check For Intersections with player
  ` -----------------------------------------------------

   For lp =0 To Max_of_Circles
     x#=Circles_Xpos#(lp)
     y#=Circles_Ypos#(lp)
     R#=Circles_Radius#(lp)
       
     ; =========================================================================
     ; Check for an intersection between our ray (from the player) and this circle.
     ; The intersection mode is set to return 2 points (if it intersects twice)
     ; as well as the normals at each intersection point.
     ; =========================================================================
     result= LineIntersectCircle(Playerx#,playery#,playerx2#,playery2#,x#,y#,R#,2+4)

  if result
     CircleC x#,y#,r#,0,RGB(255,0,0)
     For IMpacts=0 to result-1
      ix#=GetIntersectX#(impacts)
      iy#=GetIntersectY#(impacts)
      Circle ix#,iy#,5,1
      nx#=GetNormalX#(impacts)
      ny#=GetNormalY#(impacts)
        linec ix#,iy#,ix#+(nx#*50),iy#+(ny#*50),rgb(0,255,0)
    next
     Else
      CircleC x#,y#,r#,0,RGB(255,255,255)
     EndIf    
   Next lp
 UnLockBuffer

 Sync
Loop