Soft Body Physics

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SoCoder -> Snippet Home -> Collisions and Physics

Scherererer	Created : 12 September 2010 System : Windows Language : Blitz Soft Body Physics Simple demo of roughly how soft bodies work
This demo is very rudimentary, but basically it demonstrates kind of how soft bodies work. The basic idea is to pretend that the lines connecting vertices have on them a spring and a damper. Then, when a force is exerted on some point (or series of points), that force can be reflected across the other points. More points means more realistic looking surfaces. Spring coefficient [0,1]: higher number->more spring, lower number->less spring Damping coefficient [0,1]: higher number->more damping; not to be confused with less springyness. "spring" resists displacement, whereas "damping" resists change in displacement (velocity). The forces applied effect the change in the change in displacement (change in velocity (acceleration)) See Calculus:erivatives and Wikipedia: Damping for more on this. The spring/dampers in this example are only connected along the square "grid" lines, however in typical/modern configurations, additional connections are made on the diagonals and over other points to compensate for polygon folding and other issues. Const Mass = 1 Const K# = .5 Const Cd# = .5;.8 Global F1# = 2, F2# = 1 Const dt# = .1 Graphics3D 800,600,32,2 Type Vertex Field v Field x#, y#, z# Field xd#, yd#, zd# Field xdd#, ydd#, zdd# End Type m=CreateMesh() s=CreateSurface( m ) Dim verts.Vertex(4,5) i=0 For r=0 To 3 For c=0 To 4 verts(r,c) = New Vertex verts(r,c)\x = r verts(r,c)\y = c AddVertex s, r, c, 0 verts(r,c)\v = i VertexColor s, verts(r,c)\v, Rnd(0,255), Rnd(0,255), Rnd(0,255) i = i + 1 Next Next For r=0 To 2 For c=0 To 3 AddTriangle s, verts(r,c)\v, verts(r,c+1)\v, verts(r+1,c+1)\v AddTriangle s, verts(r,c)\v, verts(r+1,c+1)\v, verts(r+1,c)\v Next Next EntityFX m, 2 light = CreateLight(2) camera = CreateCamera() MoveEntity camera, -.1, -.1, -3 TurnEntity camera, -20, -20, 0 While (Not KeyDown(1)) For r=1 To 2 For c=1 To 3 v.Vertex = verts(r,c) v\xdd = K(DiplacementX#(r, c)) + Cd(DiplacementXD#(r, c)) v\ydd = K(DiplacementY#(r, c)) + Cd(DiplacementYD#(r, c)) v\zdd = K(DiplacementZ#(r, c)) + Cd(DiplacementZD#(r, c)) If (c = 2 And r = 1) v\zdd = v\zdd + F1 EndIf If (c = 2 And r = 2) v\zdd = v\zdd + F2 EndIf v\xd = v\xd + v\xdddt v\yd = v\yd + v\ydddt v\zd = v\zd + v\zdddt v\x = v\x + (v\xd)dt v\y = v\y + (v\yd)dt v\z = v\z + (v\zd)dt VertexCoords s, v\v, v\x, v\y, v\z Next Next If (KeyDown(200)) F1 = F1 + .1 ElseIf (KeyDown(208)) F1 = F1 - .1 EndIf UpdateWorld RenderWorld Text 0,00,"Force 1: " + F1 Text 0,13,"Force 2: " + F2 Text 0,26,"Spring Coeff: " + K Text 0,39,"Damping Coeff: " + Cd VWait : Flip False Wend Function DiplacementX#(r%, c%) Return verts(r+1,c)\x + verts(r-1,c)\x + verts(r,c+1)\x + verts(r,c-1)\x - (verts(r,c)\x4) End Function Function DiplacementY#(r%, c%) Return verts(r+1,c)\y + verts(r-1,c)\y + verts(r,c+1)\y + verts(r,c-1)\y - (verts(r,c)\y4) End Function Function DiplacementZ#(r%, c%) Return verts(r+1,c)\z + verts(r-1,c)\z + verts(r,c+1)\z + verts(r,c-1)\z - (verts(r,c)\z4) End Function Function DiplacementXD#(r%, c%) Return verts(r+1,c)\xd + verts(r-1,c)\xd + verts(r,c+1)\xd + verts(r,c-1)\xd - (verts(r,c)\xd4) End Function Function DiplacementYD#(r%, c%) Return verts(r+1,c)\yd + verts(r-1,c)\yd + verts(r,c+1)\yd + verts(r,c-1)\yd - (verts(r,c)\yd4) End Function Function DiplacementZD#(r%, c%) Return verts(r+1,c)\zd + verts(r-1,c)\zd + verts(r,c+1)\zd + verts(r,c-1)\zd - (verts(r,c)\zd4) End Function --v

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Sunday, 12 September 2010, 23:48
Jayenkai	ooooh, bouncy!

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