PureBoard

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EnableExplicit

Procedure.l col_line_line(x1.f,y1.f,x2.f,y2.f,x3.f,y3.f,x4.f,y4.f)
  ;check if two lines collide
  ;modified code from: Stargate (PB Forums)
  
  Protected cross_prod_a.f
  Protected cross_prod_b.f
  Protected new_vectorX.i
  Protected new_VectorY.i
  Protected comp.f
  
  cross_prod_a = (x2-x1)*(y4-y3) - (x4-x3)*(y2-y1)
  
  If cross_prod_a
    
    new_vectorX = x3 - x1
    new_VectorY = y3 - y1
    
    cross_prod_b = new_vectorX * (y4-y3) - new_VectorY * (x4-x3)
    
    comp = cross_prod_b / cross_prod_a
    
    If comp >= 0 And comp <= 1
      
      cross_prod_b = new_vectorX * (y2-y1) - new_VectorY * (x2-x1)
      
      comp = cross_prod_b / cross_prod_a
      
      If comp >= 0 And comp <= 1
        
        ProcedureReturn #True
        
      EndIf
      
    EndIf
    
  EndIf
  
  ProcedureReturn #False
  
EndProcedure

Procedure.l col_point_tri(t1x.f,t1y.f,t2x.f,t2y.f,t3x.f,t3y.f,Px.f,Py.f)
  ;check if point lies in the triangle
  
  Protected r.f
  Protected s.f
  Protected result.f
  
  Protected Ax.f = t2x - t1x
  Protected Ay.f = t2y - t1y
  Protected Bx.f = t3x - t1x
  Protected By.f = t3y - t1y
  
  Px - t1x
  Py - t1y
  
  If By = 0
    By = 0.0001
  EndIf
  
  r = (By*Ax-Ay*Bx)
  
  If r 
    r      = (Px*By-Bx*Py)/r
    s      = (Py-Ay*r)/By
    result = r+s
    
    If result <= 1 And result => 0 And r <= 1 And r => 0 And s <= 1 And s => 0
      ProcedureReturn #True
    EndIf
  EndIf
  
  ProcedureReturn #False
  
EndProcedure

Procedure collision(a1x.i,a1y.i,a2x.i,a2y.i,a3x.i,a3y.i,b1x.i,b1y.i,b2x.i,b2y.i,b3x.i,b3y.i)
  
  If col_point_tri(a1x,a1y,a2x,a2y,a3x,a3y,b1x,b1y) Or col_point_tri(a1x,a1y,a2x,a2y,a3x,a3y,b2x,b2y) Or col_point_tri(a1x,a1y,a2x,a2y,a3x,a3y,b3x,b3y)
    ProcedureReturn #True
  ElseIf col_point_tri(b1x,b1y,b2x,b2y,b3x,b3y,a1x,a1y) Or col_point_tri(b1x,b1y,b2x,b2y,b3x,b3y,a2x,a2y) Or col_point_tri(b1x,b1y,b2x,b2y,b3x,b3y,a3x,a3y)
    ProcedureReturn #True
  ElseIf col_line_line(a1x,a1y,a2x,a2y,b1x,b1y,b2x,b2y) Or col_line_line(a2x,a2y,a3x,a3y,b1x,b1y,b2x,b2y) Or col_line_line(a3x,a3y,a1x,a1y,b1x,b1y,b2x,b2y) 
    ProcedureReturn #True
  ElseIf col_line_line(a1x,a1y,a2x,a2y,b2x,b2y,b3x,b3y) Or col_line_line(a2x,a2y,a3x,a3y,b2x,b2y,b3x,b3y) Or col_line_line(a3x,a3y,a1x,a1y,b2x,b2y,b3x,b3y) 
    ProcedureReturn #True
  ElseIf col_line_line(a1x,a1y,a2x,a2y,b3x,b3y,b1x,b1y) Or col_line_line(a2x,a2y,a3x,a3y,b3x,b3y,b1x,b1y) Or col_line_line(a3x,a3y,a1x,a1y,b3x,b3y,b1x,b1y)
    ProcedureReturn #True
  EndIf
  
  ProcedureReturn #False
  
EndProcedure

Define a1x.i,a1y.i,a2x.i,a2y.i,a3x.i,a3y.i,b1x.i,b1y.i,b2x.i,b2y.i,b3x.i,b3y.i

;no hit

a1x = 1 : a1y = 1
a2x = 3 : a2y = 4
a3x = 5 : a3y = 1

b1x = 4 : b1y = 3
b2x = 9 : b2y = 3
b3x = 6 : b3y = 0

Debug collision(a1x,a1y,a2x,a2y,a3x,a3y,b1x,b1y,b2x,b2y,b3x,b3y)

;hit (one edge in another triangel)

a1x = 1 : a1y = 1
a2x = 4 : a2y = 4
a3x = 5 : a3y = 1

b1x = 3 : b1y = 2
b2x = 7 : b2y = 2
b3x = 6 : b3y = 4

Debug collision(a1x,a1y,a2x,a2y,a3x,a3y,b1x,b1y,b2x,b2y,b3x,b3y)

;hit (only crossing lines)

a1x = 1 : a1y = 1
a2x = 3 : a2y = 4
a3x = 5 : a3y = 1

b1x = 1 : b1y = 3
b2x = 5 : b2y = 3
b3x = 3 : b3y = 0

Debug collision(a1x,a1y,a2x,a2y,a3x,a3y,b1x,b1y,b2x,b2y,b3x,b3y)