DrawPoly and DrawLine produce different results?

BlitzMax Forums/BlitzMax Programming/DrawPoly and DrawLine produce different results?

Grisu

(Posted 2012) [#1]

Hi there!

I'm trying to create a pixel-perfect outline for my wave display.

DrawLine and DrawPoly in some cases fill out different positions.
The result are disturbing "empty" pixels between the line and the drawn poly itself as shown below.

Screenshot:

Example code: (needs Bah.fmod and MaxGui to run)

' OutLine Example
SuperStrict

Framework MaxGui.Drivers
Import BAH.FMOD
Import BRL.GLMax2d
Import BRL.StandardIO
Import BRL.PNGLoader
Import BRL.Pixmap
Import BRL.EventQueue
Import BRL.Timer

Const MAINWINDOW_W:Int = 278 
Const MAINWINDOW_H:Int = 154
Const url:String = "http://scfire-ntc-aa04.stream.aol.com:80/stream/1074" '<- Place your Radio IP here
Const SpectrumSize:Int = 64
Const SPECTRUM_GROUP_SIZE:Int = (SpectrumSize/2)

Global f_Sensitivity:Float = 100.0	
Global timer:TTimer=CreateTimer(35)

Local system:TFMODSystem = New TFMODSystem.Create()
system.Init(1)

Global sound:TFMODSound = system.CreateStreamURL(url,Null)
Global channel:TFMODChannel

Print ""
Print "Connecting to: "+url

channel = system.PlaySound(Null, sound)

Local spectrum:Float[SpectrumSize]
Global icol:Int
Global flags:Int=WINDOW_TITLEBAR|WINDOW_CENTER|WINDOW_RESIZABLE
Global window:TGadget=CreateWindow("Red outline not precise",30,20,MAINWINDOW_W+8,MAINWINDOW_H+70,Null, flags)
Global Button2:TGadget=CreateButton("Exit APP",6,MAINWINDOW_H+2,MAINWINDOW_W-18,20,window,BUTTON_OK)

Global RadioStationCanvas:TGadget = CreateCanvas(2, 2, 274, 87, window, PANEL_ACTIVE) '110
Global station_logo:TPixmap 
Global _logo2:TPixmap
'_Logo2:TPixmap=LoadPixmap("station_ico.png") 

SetGraphics CanvasGraphics( RadioStationCanvas )
SetClsColor 255,255,255

While WaitEvent()
	Select EventID()
		Case EVENT_WINDOWCLOSE
			End
		Case EVENT_GADGETACTION
   	 	      Select EventSource() 
                 Case BUTTON2
                      system.Close()
					  system.SystemRelease()
			          End 
                 End Select 

       Case EVENT_TIMERTICK ' Do fancy Spectrum stuff

       SetGraphics CanvasGraphics( RadioStationCanvas )
'       Cls
'       DrawPixmap _Logo2,0,0  
       SetBlend SOLIDBLEND 
       Cls

       If channel.GetSpectrum(spectrum, 0,FMOD_DSP_FFT_WINDOW_TRIANGLE) = FMOD_OK Then ' Left Spectrum
          DrawSpectrumL_Hills(spectrum)
       EndIf 

       If channel.GetSpectrum(spectrum, 1,FMOD_DSP_FFT_WINDOW_TRIANGLE) = FMOD_OK Then ' Right Spectrum
           DrawSpectrumR_Hills(spectrum)
       EndIf 

       Flip()
	End Select
 
     system.Update()

Wend 

Function DrawSpectrumL_Hills(_spectrum:Float[])
	If _spectrum And _spectrum.length
		Local index_offset:Float = 0
		Const bar_width:Int = 1
        Local xold:Float = -999
        Local yold:Float = -999 
        Local val:Float = 0 
        Local tri#[] 
        Local c:Int=1
      
		For Local f_val:Float = EachIn _spectrum          
            If c<19 Then 
		    val=-f_val*500
     	    If val<-86 Then val=-86

			If xold=-999 Then 		
             xold=bar_width+index_offset
             yold=val

            Else    

             SetBlend ALPHABLEND 
             SetAlpha( 0.75 )
             SetColor 80,80,80
             If yold => val Then 
                DrawRect (xold,-1*yold,8,yold) ' |/"
                tri#=[xold,-1*yold,xold+8,-1*yold,bar_width+index_offset,-1*val] 
                DrawPoly tri# 
             Else
                DrawRect (xold,-1*val,8,val) ' \|"
                tri#=[xold,-1*val,xold+8,-1*val,xold,-1*yold] 
                DrawPoly tri# 
             EndIf  
             SetColor 255,0,0
             DrawLine xold,-1*yold,bar_width+index_offset,-1*val
         
             xold=bar_width+index_offset
             yold=val
            EndIf  
			index_offset :+ 8

            Else 
            Exit
            EndIf 

            c:+1 
		Next
	EndIf
End Function

Function DrawSpectrumR_Hills(_spectrum:Float[])
	If _spectrum And _spectrum.length
		Local index_offset:Int = 272
		Const bar_width:Float = 1
        Local xold:Float = -999
        Local yold:Float = -999 
        Local val:Float = 0 
        Local tri#[] 
        Local c:Int=1
      
		For Local f_val:Float = EachIn _spectrum          
            If c<19 Then 
		    val=-f_val*500
     	    If val<-86 Then val=-86

			If xold=-999 Then 		
             xold=bar_width+index_offset
             yold=val

            Else    

             SetBlend ALPHABLEND 
             SetAlpha( 0.75 )
             SetColor 20,20,20
             If yold => val Then 
                DrawRect (xold,-1*yold,-8,yold) ' |/"
                tri#=[xold,-1*yold,xold-8,-1*yold,bar_width+index_offset,-1*val] 
                DrawPoly tri# 
             Else
                DrawRect (xold,-1*val,-8,val) ' \|"
                tri#=[xold,-1*val,xold-8,-1*val,xold,-1*yold] 
                DrawPoly tri# 
             EndIf  
             SetColor 255,0,0
             DrawLine xold,-1*yold,bar_width+index_offset,-1*val
           
             xold=bar_width+index_offset
             yold=val
            EndIf  
			index_offset :- 8

            Else 
            Exit
            EndIf 

            c:+1 
		Next
	EndIf
End Function

Is there a way got get rid of these empty spaces?

Grisu

Last edited 2012