how would you draw a rainbow?

Comments

• hgy29 Maintainer

  December 2016 edited December 2016

  I would use seven coloured arcs (Path2D), slightly overlapping each other. Let me try to write somethinh in LUA
  
  EDIT: Something like that ?

  Rainbow=Core.class(Sprite) Rainbow.arcCol={ 0xFF0000, 0xFF8000, 0xFFFF00, 0x00FF00, 0x00FFFF, 0x0000FF,0xC000C0}   function Rainbow:Arc(ta,n,angs,ange) local sw=(self.radiusMax-self.radiusMin)/7 local lr=sw*n+self.radiusMin ta:setLineColor(self.arcCol[n],1) ta:setFillColor(0,0) ta:setPath("MA", math.sin(angs*math.pi/180)*lr,-math.cos(angs*math.pi/180)*lr, lr,lr,0,0,1, math.sin(ange*math.pi/180)*lr,-math.cos(ange*math.pi/180)*lr) ta:setLineThickness(sw*2,0.5) return ta end     function Rainbow:init(radius,width) self.radiusMin,self.radiusMax=radius-width/2,radius+width/2 for i=1,7 do self:addChild(Path2D.new()) end self:setAngles(-90,90) end   function Rainbow:setAngles(angs,ange) for i=1,7 do self:Arc(self:getChildAt(i),i,angs,ange) end end     application:setBackgroundColor(0) local rainbow=Rainbow.new(80,20) rainbow:setPosition(100,100) stage:addChild(rainbow)   stage:addEventListener(Event.ENTER_FRAME,function () local frame=Core.frameStatistics().frameCounter local ratio=math.abs((frame%120)-60)/60 rainbow:setAngles(-90,-90+180*ratio) end)

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• pie Member

  December 2016

  awesome! thank you!
  
  I am not sure I understand it completely though (my weak math skills.. :-B )
  May I use yours again?
  
  Do you think it's possible to tweak this so that it disappears from its origin instead of "rewinding" itself (see previous gif)?
  
  How would you link it to 2 dynamic points (ie 2 clicks - first to set the origin, the other to set the "pot of gold" ) ?
  I thought about using skew, but how do I translate coordinates on screen to the "right" skewing value?
  
  
  thank you a lot!

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• hgy29 Maintainer

  December 2016 Accepted Answer

  Try this one, I hope you can make sense of it somehow..

  Rainbow=Core.class(Sprite) Rainbow.arcCol={ 0xFF0000, 0xFF8000, 0xFFFF00, 0x00FF00, 0x00FFFF, 0x0000FF,0xC000C0}   function Rainbow:Arc(ta,n,angs,ange) local sw=(self.radiusMax-self.radiusMin)/7 local lr=sw*n+self.radiusMin ta:setLineColor(self.arcCol[n],1) ta:setFillColor(0,0) ta:setPath("MA", math.sin(angs*math.pi/180)*lr,-math.cos(angs*math.pi/180)*lr, lr,lr,0,0,1, math.sin(ange*math.pi/180)*lr,-math.cos(ange*math.pi/180)*lr) ta:setLineThickness(sw*2,0.5) return ta end     function Rainbow:init(radius,width) self.radiusMin,self.radiusMax=radius-width/2,radius+width/2 for i=1,7 do self:addChild(Path2D.new()) end self:setAngles(-90,90) end   function Rainbow:setRadius(radius,width) self.radiusMin,self.radiusMax=radius-width/2,radius+width/2 end   function Rainbow:setAngles(angs,ange) for i=1,7 do self:Arc(self:getChildAt(i),i,angs,ange) end end     application:setBackgroundColor(0) local rainbow=Rainbow.new(80,20) rainbow:setPosition(100,100) stage:addChild(rainbow)   local animSpeed=120 local sposx,sposy=100,100 local scrw,scrh=application:getContentWidth(),application:getContentHeight() local angs=-90 stage:addEventListener(Event.ENTER_FRAME,function () local frame=Core.frameStatistics().frameCounter local frameIndex=frame%animSpeed local ratio=(frameIndex-animSpeed/2)/(animSpeed/2) if frameIndex==0 then local nposx,nposy=math.random(scrw),math.random(scrh) local cx,cy=(nposx+sposx)/2,(nposy+sposy)/2 rainbow:setPosition(cx,cy) local mrad=math.sqrt(((sposx-cx)^2)+((sposy-cy)^2)) rainbow:setRadius(mrad,20) local dx,dy=(sposx-cx),-(sposy-cy) angs=math.atan2(dx,dy)*180/math.pi sposx,sposy=nposx,nposy end local ange=angs+180 if ratio<0 then rainbow:setAngles(angs,ange+180*ratio) else rainbow:setAngles(angs+180*ratio,ange) end end)

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• pie Member

  December 2016

  Thank you heaps!
  now I must study it

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