DrawPoly

Monkey Forums/Monkey Programming/DrawPoly

degac (Posted 2011) [#1]

Hi there are plans to add DrawPoly (filled) command to Monkey? I think it will be handy.

invaderJim (Posted 2011) [#2]

This is the best I could do porting over some old code from the blitzmax forums. You can either draw a poly by passing a list of vertices, or by specifying a number of sides and a radius. If you try the latter method, you will see that I'm having issues with spacing between the triangles. Fun fun... example.monkey: Import mojo Import drawpoly Class DrawPolyTest Extends App Field polyAng:Float = 0.0 Field poly1:List<PolyVertex> = New List<PolyVertex>() Method New() End Method OnCreate() SetUpdateRate(30) poly1.AddLast(New PolyVertex(50.0, 400.0)) poly1.AddLast(New PolyVertex(100.0, 400.0)) poly1.AddLast(New PolyVertex(100.0, 450.0)) poly1.AddLast(New PolyVertex(75.0, 425.0)) poly1.AddLast(New PolyVertex(50.0, 450.0)) End Method OnUpdate() End Method OnRender() Cls 0, 0, 0 DrawTriangle(100, 100, 100, 200, 200, 200, True, 255, 255, 255) ' DrawPoly(centerX, centerY, numSides, radius, rotation, filled, r, g, b) DrawPoly(200, 200, 6, 70, polyAng, True, 0, 255, 0) DrawPoly(poly1, True) If Not KeyDown(KEY_SPACE) Then polyAng += 1 End End Function Main() New DrawPolyTest End drawpoly.monkey: Import mojo.graphics Class PolyVertex Field x:Float Field y:Float Method New(_x:Float, _y:Float) x = _x y = _y End End Class PolyTri Field p1:PolyVertex Field p2:PolyVertex Field p3:PolyVertex Method New(_p1:PolyVertex, _p2:PolyVertex, _p3:PolyVertex) p1 = _p1 p2 = _p2 p3 = _p3 End End ' ******* Re-write. Based on Axel Wheeler's post on: <a href="http://www.blitzbasic.com/Community/posts.php?topic=93985" target="_blank">http://www.blitzbasic.com/Community/posts.php?topic=93985</a> Function DrawTriangle(x0:Float, y0:Float, x1:Float, y1:Float, x2:Float, y2:Float, filled:Bool = False, r:Int = 255, g:Int = 255, b:Int = 255) SetColor(r, g, b) If filled Local Ya:Float=Ceil(y0) Local Xa:Float=x0 Local Yb:Float=Ceil(y1) Local Xb:Float=x1 Local Yc:Float=Ceil(y2) Local Xc:Float=x2 Local Xlong:Float Local Xshort:Float Local Xtemp:Float Local Ytemp:Float If Yb<Ya Xtemp=Xa Ytemp=Ya Xa=Xb Ya=Yb Xb=Xtemp Yb=Ytemp EndIf If Yc<Ya Xtemp=Xa Ytemp=Ya Xa=Xc Ya=Yc Xc=Xtemp Yc=Ytemp EndIf If Yc<Yb Xtemp=Xb Ytemp=Yb Xb=Xc Yb=Yc Xc=Xtemp Yc=Ytemp EndIf Local slopeAC:Float = 0.0, slopeAB:Float = 0.0, slopeBC:Float = 0.0 If Yc <> Ya Then slopeAC = (Xc-Xa)/(Yc-Ya) If Yb <> Ya Then slopeAB = (Xb-Xa)/(Yb-Ya) If Yb <> Yc Then slopeBC = (Xc-Xb)/(Yc-Yb) For Local y:= Ya To Yc Xlong = Xa+((y-Ya)*slopeAC) If y < Yb Xshort = Xa+((y-Ya)*slopeAB) Else Xshort = Xb+((y-Yb)*slopeBC) End DrawLine(Xlong,y,Xshort,y) Next Else DrawLine(x0,y0,x1,y1) DrawLine(x1,y1,x2,y2) DrawLine(x2,y2,x0,y0) End End Function DrawPoly(centerX:Int, centerY:Int, numSides:Int, radius:Float, rotation:Float = 0.0, filled:Bool = False, r:Int = 255, g:Int = 255, b:Int = 255) Local polyList:List<PolyVertex> = New List<PolyVertex>() Local angInc:Float = 360.0/numSides For Local i:= 1 To numSides Local x:Float = centerX + Sin(rotation)*radius Local y:Float = centerY - Cos(rotation)*radius polyList.AddLast(New PolyVertex(x, y)) rotation += angInc Next DrawPoly(polyList, filled, r, g, b) End Function DrawPoly(polys:List<PolyVertex>, filled:Bool = False, r:Int = 255, g:Int = 255, b:Int = 255) If filled Local tris:List<PolyTri> = TriangulatePoly(polys) For Local tTri:= Eachin tris DrawTriangle(tTri.p1.x, tTri.p1.y, tTri.p2.x, tTri.p2.y, tTri.p3.x, tTri.p3.y, True, r, g, b) Next Else SetColor(r, g, b) Local ac:Int = polys.Count() Local count:= 0 Local polyArray:PolyVertex[ac] For Local tVert:= Eachin polys polyArray[count] = tVert count += 1 Next For Local i:= 0 To ac-1 Local x1:= polyArray[i].x Local y1:= polyArray[i].y Local x2:= polyArray[(i+1) Mod ac].x Local y2:= polyArray[(i+1) Mod ac].y DrawLine(x1, y1, x2, y2) Next i EndIf End ' ******* Conversion from Warpy's post on: <a href="http://www.blitzbasic.com/Community/posts.php?topic=78165" target="_blank">http://www.blitzbasic.com/Community/posts.php?topic=78165</a> Function TriangulatePoly:List<PolyTri>(polys:List<PolyVertex>) Local polyCopy:List<PolyVertex> = New List<PolyVertex>() Local c:= polys.Count() For Local tPoly:= Eachin polys polyCopy.AddLast(New PolyVertex(tPoly.x, tPoly.y)) Next If c < 3 Then Return Null Local l:List<PolyTri> = New List<PolyTri>() 'this list will store all our triangles While c>3 Local polyArray:PolyVertex[c] Local count:= 0 For Local tp:= Eachin polyCopy polyArray[count] = tp count += 1 Next Local i:= 0 Local go:= 0 Local p1:PolyVertex, p2:PolyVertex, p3:PolyVertex While Not go p1 = polyArray[i] p2 = polyArray[(i+1) Mod c] p3 = polyArray[(i+2) Mod c] 'p1,p2,p3 are consecutive points on the boundary of the polygon. 'consider the triangle p1->p2->p3 Local midx:Float = (p1.x + p2.x + p3.x) / 3.0 '(midx,midy) is a point inside the candidate triangle Local midy:Float = (p1.y + p2.y + p3.y) / 3.0 'here we check if (midx,midy) is inside the polygon. An 'S'-bend in the polygon can cause the candidate triangle 'to actually be on the outside of the polygon, making it useless in a triangulation. 'This check works by counting the number of times a horizontal ray originating from (midx,midy) crosses the boundary of the polygon 'if hits is odd, then (midx,midy) is inside the polygon. Local hits:=0 For Local ii:= 0 To c - 1 Local x1:Float=polyArray[ii].x Local y1:Float=polyArray[ii].y Local x2:Float=polyArray[(ii+1) Mod c].x Local y2:Float=polyArray[(ii+1) Mod c].y If (y1-midy)*(y2-midy)<0 Local ix:Float = x1+(x2-x1)*(midy-y1)/(y2-y1) If ix<midx hits += 1 EndIf Next If (hits Mod 2) 'tri is inside polygon 'We now know the triangle is inside the polygon, so the last thing we need to check is that the line p3->p1 'doesn't cross the boundary at any point. Local x1:Float=p1.x Local y1:Float=p1.y Local x2:Float=p3.x Local y2:Float=p3.y Local dx1:Float=x2-x1 Local dy1:Float=y2-y1 go=1 Local n:= (i+3) Mod c While n<>i Local x3:Float=polyArray[n].x Local y3:Float=polyArray[n].y Local dx2:Float=x3-x2 Local dy2:Float=y3-y2 If dx1<>dx2 Or x1<>x2 Or dy1<>dy2 Or y1<>y2 Local lambda:Float=(y2-y1+dy2*(x1-x2)/dx2)/(dy1-dx1*dy2/dx2) Local mu:Float=(x1-x2+lambda*dx1)/dx2 If lambda>0 And lambda<1 If mu>=0 And mu<=1 go=0 EndIf EndIf EndIf x2=x3 y2=y3 n=(n+1) Mod c Wend EndIf If Not go 'if go=0, then our line crossed the boundary at some point, so this triangle isn't an ear. i=(i+1) Mod c If i=0 Return Null EndIf Wend 'remove p2 from the list of points - this is the same as removing the whole ear from the polygon - now there is no way 'p1->p2->p3 will be considered again. polyCopy.Remove(p2) l.AddLast(New PolyTri(p1, p2, p3)) c -= 1 'we've removed a point Wend 'we're left with a single triangle, but it's not in our list of ears yet, so we need to add it Local polyArray:PolyVertex[c] Local count:= 0 For Local tp:= Eachin polyCopy polyArray[count] = tp count += 1 Next l.AddLast(New PolyTri(polyArray[0], polyArray[1], polyArray[2])) 'done! return the list of triangles Return l End

degac (Posted 2011) [#3]

Hi Thanks for your contribution, but I think a 'native' solution should be better: I've already changed mojo-html5 to handle DrawPoly, and I'm sure it could be done in all the other platforms.

invaderJim (Posted 2011) [#4]

Yeah, I noticed you had done that shortly after posting :P I wasn't aware that it was so easy to 'hack' mojo like that. Following your example, I've fixed my triangle drawing problem by natively drawing them in each platform. I went with just triangles to reduce the amount of code required to triangulate the polygons properly in each platform, plus I really like warpy's triangulation method ;) If you or anyone else is interested, I can post all of my DrawTriangle() functions here, but, for the most part, all I did was copy and modify the DrawRect() functions to draw one tri instead of two.

degac (Posted 2011) [#5]

Well, the 'Monkey Code Section' is here to be filled! Each new hack/function is welcomed! (and maybe Mark could be impressed/interested/stimulated enough to port the changes as 'official' in mojo...

hardcoal (Posted 2011) [#6]

Can you draw poly as lines only without fill?

Jesse (Posted 2011) [#7]

No. It shouldn't be too hard for you too implement.

hardcoal (Posted 2011) [#8]

ok good to know. tnx