Lerp or Linear Interpolation question.

Author

Message

Stormwire

14

Years of Service

User Offline

Joined: 3rd Sep 2010

Location:

Posted: 15th Jan 2012 08:49 Edited at: 15th Jan 2012 08:50

Link

I have the Lerp function working but I was wondering if anyone could tell me how I can get more points between the two initial points so I can draw an actual line and not just dots. Right now it is always 10 points no matter how far away the points are from each other. I know why this is but what I am looking for is how to add more points and take away points depending on how far the two initial points are from each other. So the closer they are the less points you would need to draw a line and the further the more points you would need. Any help is appreciated

SetVirtualResolution(480,480)

Global dot1
Global dot2
Global line

myimage = LoadImage("1.png")
dot1 = CreateSprite(myimage)
SetSpriteSize(dot1,4,4)
dot2 = CloneSprite(dot1)

count1 = 0
count2 = 0
space = 32
esc = 27

Dim x_arr#[9]
Dim y_arr#[9]

posx1# = 20.0
posy1# = 20.0

posx2# = 80.0
posy2# = 80.0

For i# = 0.0 To 1.0 Step 0.1
    
    x_arr#[count1] = Lerp(posx1#,posx2#,i#)
    y_arr#[count1] = Lerp(posy1#,posy2#,i#)
    
    Inc count1
Next i#

SetSpritePosition(dot1,posx1#,posy1#)
SetSpritePosition(dot2,posx2#,posy2#)

For i# = 0.0 To 1.0 Step 0.1
    
    line = CloneSprite(dot2)
    SetSpriteColor(line,0,100,255,255)
    SetSpritePosition(line,x_arr#[count2],y_arr#[count2])
    
    Inc count2
Next i#

Do
    
    If GetRawKeyPressed(space) = 1
        
        DeleteSprites()
        
        posx1# = Random(20.0,400.0)
        posy1# = Random(20.0,400.0)

posx2# = Random(80.0,400.0)
        posy2# = Random(80.0,400.0)
        
        SetSpriteSize(dot1,4,4)
        dot2 = CloneSprite(dot1)
        
        count1 = 0
        count2 = 0
        
        For i# = 0.0 To 1.0 Step 0.1
            
            x_arr#[count1] = Lerp(posx1#,posx2#,i#)
            y_arr#[count1] = Lerp(posy1#,posy2#,i#)
            
            Inc count1
        Next i#
        
        SetSpritePosition(dot1,posx1#,posy1#)
        SetSpritePosition(dot2,posx2#,posy2#)
        
        For i# = 0.0 To 1.0 Step 0.1
            
            line = CloneSprite(dot2)
            SetSpriteColor(line,0,100,255,255)
            SetSpritePosition(line,x_arr#[count2],y_arr#[count2])
            
            Inc count2
        Next i#
        
    EndIf
    
    Print("Press Space")
    
    Sync()
Loop

Function Lerp(p1#,p2#,i#)
    
    result# = p1#*(1-i#)+p2#*i#
    
EndFunction result#

Function DeleteSprites()
    
    For i = 10002 To line
        
        DeleteSprite(i)
        
    Next i
    
EndFunction

+ Code Snippet

SetVirtualResolution(480,480)

Global dot1
Global dot2
Global line

myimage = LoadImage("1.png")
dot1 = CreateSprite(myimage)
SetSpriteSize(dot1,4,4)
dot2 = CloneSprite(dot1)

count1 = 0
count2 = 0
space = 32
esc = 27

Dim x_arr#[9]
Dim y_arr#[9]

posx1# = 20.0
posy1# = 20.0

posx2# = 80.0
posy2# = 80.0

For i# = 0.0 To 1.0 Step 0.1
    
    x_arr#[count1] = Lerp(posx1#,posx2#,i#)
    y_arr#[count1] = Lerp(posy1#,posy2#,i#)
    
    Inc count1
Next i#

SetSpritePosition(dot1,posx1#,posy1#)
SetSpritePosition(dot2,posx2#,posy2#)

For i# = 0.0 To 1.0 Step 0.1
    
    line = CloneSprite(dot2)
    SetSpriteColor(line,0,100,255,255)
    SetSpritePosition(line,x_arr#[count2],y_arr#[count2])
    
    Inc count2
Next i#

Do
    
    If GetRawKeyPressed(space) = 1
        
        DeleteSprites()
        
        posx1# = Random(20.0,400.0)
        posy1# = Random(20.0,400.0)

        posx2# = Random(80.0,400.0)
        posy2# = Random(80.0,400.0)
        
        SetSpriteSize(dot1,4,4)
        dot2 = CloneSprite(dot1)
        
        count1 = 0
        count2 = 0
        
        For i# = 0.0 To 1.0 Step 0.1
            
            x_arr#[count1] = Lerp(posx1#,posx2#,i#)
            y_arr#[count1] = Lerp(posy1#,posy2#,i#)
            
            Inc count1
        Next i#
        
        SetSpritePosition(dot1,posx1#,posy1#)
        SetSpritePosition(dot2,posx2#,posy2#)
        
        For i# = 0.0 To 1.0 Step 0.1
            
            line = CloneSprite(dot2)
            SetSpriteColor(line,0,100,255,255)
            SetSpritePosition(line,x_arr#[count2],y_arr#[count2])
            
            Inc count2
        Next i#
        
    EndIf
    
    Print("Press Space")
    
    Sync()
Loop

Function Lerp(p1#,p2#,i#)
    
    result# = p1#*(1-i#)+p2#*i#
    
EndFunction result#

Function DeleteSprites()
    
    For i = 10002 To line
        
        DeleteSprite(i)
        
    Next i
    
EndFunction

Back to top

Profile PM Email

baxslash

Valued Member

Bronze Codemaster

17

Years of Service

User Offline

Joined: 26th Dec 2006

Location: Duffield

Posted: 15th Jan 2012 10:33

Link

I would divide the overall distance by your maximum distance between segments and use the answer as your "step" amount in the "for" loop at the start. Hope that makes sense?

Back to top

Profile PM Email

Preben

AGK Studio Developer

20

Years of Service

User Offline

Joined: 30th Jun 2004

Location:

Posted: 15th Jan 2012 10:50

Link

This will calculate how many points you need to make a line.

+ Code Snippet

pointsneeded = sqrt( (posx1#-posx2#)^2 + (posy1#-posy2#)^2 )

This will draw a line using one sprite.

+ Code Snippet

posx1# = 20.0
posy1# = 20.0
posx2# = 80.0
posy2# = 80.0

global pensize = 2
global maxlines = 1
dim spritelines[ maxlines ]
spritelines[1] = createSprite ( 0 )
setSpriteSize ( spritelines[1] , pensize, pensize )
SetSpriteColor ( spritelines[1] , 255 , 255 , 255 , 255 )
SetSpritePosition( spritelines[1] , 1000 , 1000 )
setSpriteAngle ( spritelines[1] , 0 )

do
   // do line
   SetSpriteColor ( spritelines[1] , 128 , 128 ,128 , 255 )
   SetSpritePosition( spritelines[1] , posx1# , posy1# )
   dx = posx1#-posx2#
   dy = posy1#-posy2#
   di = sqrt( (dx)^2 + (dy)^2 ) // calc dist
   setSpriteSize ( spritelines[1] , pensize, di )
   SetSpriteOffset( spritelines[1] , 1 , 1 )
   sngAngle = aTanFull( dx , dy )
   setSpriteAngle ( spritelines[1] , sngAngle )
 Sync(  )
loop

Snippets from my vector draw code, not tested, just made here but should work.

best regards Preben Eriksen,

Back to top

Profile PM Email

Daniel TGC

Retired Moderator

17

Years of Service

User Offline

Joined: 19th Feb 2007

Location: TGC

Posted: 15th Jan 2012 18:16

Link

It's not AppGameKit code but if you understand darkbasic professional there's a video tutorial at http://forum.thegamecreators.com/?m=forum_view&t=192286&b=1 you can view that for the basic code and convert it to AppGameKit easily enough. when I've got a moment I'll get around to it myself.

Back to top

Profile PM Email Website

Stormwire

14

Years of Service

User Offline

Joined: 3rd Sep 2010

Location:

Posted: 16th Jan 2012 11:01

Link

@baxslash:

Thanks I think what your saying is what Preben wrote? You wrote something similar in Daniels UFC thread.

@Preben:

Works perfect and your line function is a great share. Cheers for that

You got a good resource for this kind of thing?

@Daniel TGC:

Your tutorial is what got me started on this lol I wanted to try the Linear instead of the Cosine interpolation since it looked easier but I got stuck on figuring out the actual number of dots needed.