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"Texture mapper", by paranoidpete

Affine texture mapped for Blitz 2D that handles only 256*256 textures. You'll need my Pic to bank function to make this work. This function doesnt clip as is but there is clipping code for it in the code database.

Code

Function TexturePolygon(x0,y0,u0,v0,x1,y1,u1,v1,x2,y2,u2,v2,i.image)

If y1<y0

temp=x0 : x0=x1 : x1=temp
          temp=y0 : y0=y1 : y1=temp
          temp=u0 : u0=u1 : u1=temp
          temp=v0 : v0=v1 : v1=temp
     EndIf
     If y2<y1

temp=x1 : x1=x2 : x2=temp
          temp=y1 : y1=y2 : y2=temp
          temp=u1 : u1=u2 : u2=temp
          temp=v1 : v1=v2 : v2=temp
     EndIf
     If y1<y0

temp=x0 : x0=x1 : x1=temp
          temp=y0 : y0=y1 : y1=temp
          temp=u0 : u0=u1 : u1=temp
          temp=v0 : v0=v1 : v1=temp
     EndIf
     
     leftdy=y1-y0 : rightdy=y2-y0
     
     If (leftdy)<>0
          leftxm=((x1-x0) Shl 8)/(leftdy)
          leftum=((u1-u0) Shl 8)/(leftdy)
          leftvm=((v1-v0) Shl 8)/(leftdy)
     EndIf
     If (rightdy)<>0
          rightxm=((x2-x0) Shl 8)/(rightdy)
          rightum=((u2-u0) Shl 8)/(rightdy)
          rightvm=((v2-v0) Shl 8)/(rightdy)
     EndIf
     
     leftx=x0 Shl 8 : rightx=x0 Shl 8
     leftu=u0 Shl 8 : rightu=u0 Shl 8
     leftv=v0 Shl 8 : rightv=v0 Shl 8
     
;higher half
     For y=y0 To y1-1
          If leftx<rightx
               lx=leftx Shr 8
               lu=leftu Shr 8
               lv=leftv Shr 8
               rx=rightx Shr 8 
               ru=rightu Shr 8
               rv=rightv Shr 8
          Else
               lx=rightx Shr 8
               lu=rightu Shr 8
               lv=rightv Shr 8
               rx=leftx Shr 8 
               ru=leftu Shr 8
               rv=leftv Shr 8
          EndIf
               deltax=rx-lx
               If deltax<>0
                    hum=((ru-lu)Shl 8)/deltax
                    hvm=((rv-lv)Shl 8)/deltax
               EndIf
               hu=lu Shl 8
               hv=lv Shl 8
               For x=lx To rx
                    u=(hu Shr 8) And $FF
                    v=hv And $FF00     
                    RGB=PeekFloat(i\bank,((v+u)Shl 2))
                    WritePixelFast(x,y,RGB)
                    hu=hu+hum
                    hv=hv+hvm
               Next     
          leftx=leftx+leftxm
          leftu=leftu+leftum
          leftv=leftv+leftvm
          rightx=rightx+rightxm
          rightu=rightu+rightum
          rightv=rightv+rightvm
     Next
     
;lower half
     leftdy=(y2-y1)
     
     If (leftdy)<>0
          leftxm=((x2-x1) Shl 8)/(leftdy)
          leftum=((u2-u1) Shl 8)/(leftdy)
          leftvm=((v2-v1) Shl 8)/(leftdy)
     EndIf
     
     leftx=x1 Shl 8
     leftu=u1 Shl 8
     leftv=v1 Shl 8
     
     For y=y1 To y2     
          If leftx<rightx
               lx=leftx Shr 8
               lu=leftu Shr 8
               lv=leftv Shr 8
               rx=rightx Shr 8
               ru=rightu Shr 8
               rv=rightv Shr 8
          Else
               lx=rightx Shr 8
               lu=rightu Shr 8
               lv=rightv Shr 8
               rx=leftx Shr 8
               ru=leftu Shr 8
               rv=leftv Shr 8
          EndIf
               deltax=(rx-lx)
               If deltax<>0
                    hum=((ru-lu)Shl 8)/deltax
                    hvm=((rv-lv)Shl 8)/deltax
               EndIf
               hu=lu Shl 8
               hv=lv Shl 8
               For x=lx To rx
                    u=(hu Shr 8) And $FF
                    v=hv And $FF00
                    RGB=PeekFloat(i\bank,((v+u)Shl 2))
                    WritePixelFast(x,y,RGB)
                    hu=hu+hum
                    hv=hv+hvm
               Next
          leftx=leftx+leftxm : rightx=rightx+rightxm
          leftu=leftu+leftum : rightu=rightu+rightum
          leftv=leftv+leftvm : rightv=rightv+rightvm
     Next
End Function

Code software created by Krylar's Kreations