#!/usr/bin/python # # Original C++ version by Daid # http://www.box2d.org/forum/viewtopic.php?f=3&t=1473 # # Python version Copyright (c) 2008 kne / sirkne at gmail dot com # # Implemented using the pybox2d SWIG interface for Box2D (pybox2d.googlecode.com) # # This software is provided 'as-is', without any express or implied # warranty. In no event will the authors be held liable for any damages # arising from the use of this software. # Permission is granted to anyone to use this software for any purpose, # including commercial applications, and to alter it and redistribute it # freely, subject to the following restrictions: # 1. The origin of this software must not be misrepresented; you must not # claim that you wrote the original software. If you use this software # in a product, an acknowledgment in the product documentation would be # appreciated but is not required. # 2. Altered source versions must be plainly marked as such, and must not be # misrepresented as being the original software. # 3. This notice may not be removed or altered from any source distribution. from test_main import * class BoxCutter (Framework): name="BoxCutter" laserBody=None _pickle_vars=['laserBody'] def __init__(self): super(BoxCutter, self).__init__() self.world.GetGroundBody().SetUserData("ground") bd=box2d.b2BodyDef() bd.position = (0.0, -10.0) bd.userData = "ground1" ground = self.world.CreateBody(bd) sd=box2d.b2PolygonDef() sd.SetAsBox(50.0, 10.0) ground.CreateShape(sd) bd=box2d.b2BodyDef() bd.position = (0.0, 50.0) bd.userData = "ground2" ground = self.world.CreateBody(bd) sd=box2d.b2PolygonDef() sd.SetAsBox(50.0, 10.0) ground.CreateShape(sd) bd=box2d.b2BodyDef() bd.position = (0.0, 1.0) bd.userData = "laser" self.laserBody = self.world.CreateBody(bd) sd=box2d.b2PolygonDef() sd.SetAsBox(5.0, 1.0) sd.density = 4.0 self.laserBody.CreateShape(sd) self.laserBody.SetMassFromShapes() sd=box2d.b2PolygonDef() sd.SetAsBox(3.0, 3.0) sd.density = 5.0 bd=box2d.b2BodyDef() bd.userData = 1 bd.position = (0.0, 8.0) body1 = self.world.CreateBody(bd) body1.CreateShape(sd) body1.SetMassFromShapes() sd=box2d.b2PolygonDef() sd.SetAsBox(3.0, 3.0) sd.density = 5.0 bd=box2d.b2BodyDef() bd.userData = 1 bd.position = (0.0, 8.0) body1 = self.world.CreateBody(bd) body1.CreateShape(sd) body1.SetMassFromShapes() # Split a shape through a segment # Returns: # False - Error on split # True - Normal result is two new shape definitions. def SplitShape(self, shape, segment, splitSize, newPolygon): b = shape.GetBody() xf = b.GetXForm() hit,lambda_,normal=shape.TestSegment(xf, segment, 1.0) if hit != box2d.e_hitCollide: return False entryPoint = (1-lambda_)*segment.p1+lambda_*segment.p2 reverseSegment=box2d.b2Segment() reverseSegment.p1=segment.p2 reverseSegment.p2=segment.p1 hit,lambda_,normal=shape.TestSegment(xf, reverseSegment, 1.0) if hit != box2d.e_hitCollide: return False exitPoint = (1-lambda_)*reverseSegment.p1+lambda_*reverseSegment.p2 localEntryPoint = b.GetLocalPoint(entryPoint) localExitPoint = b.GetLocalPoint(exitPoint) vertices = shape.getVertices_b2Vec2() cutAdded = [-1,-1] last = -1 for i in range(shape.GetVertexCount()): #Find out if this vertex is on the old or new shape. if box2d.b2Dot(box2d.b2Cross(localExitPoint-localEntryPoint, 1), vertices[i]-localEntryPoint) > 0: n = 0 else: n = 1 if last != n: #If we switch from one shape to the other add the cut vertices. if last == 0: assert(cutAdded[0]==-1) cutAdded[0] = newPolygon[last].vertexCount newPolygon[last].setVertex(newPolygon[last].vertexCount, localExitPoint) newPolygon[last].vertexCount+=1 newPolygon[last].setVertex(newPolygon[last].vertexCount, localEntryPoint) newPolygon[last].vertexCount+=1 elif last == 1: assert(cutAdded[last]==-1) cutAdded[last] = newPolygon[last].vertexCount newPolygon[last].setVertex(newPolygon[last].vertexCount, localEntryPoint) newPolygon[last].vertexCount+=1 newPolygon[last].setVertex(newPolygon[last].vertexCount, localExitPoint) newPolygon[last].vertexCount+=1 newPolygon[n].setVertex(newPolygon[n].vertexCount, vertices[i]) newPolygon[n].vertexCount+=1 last = n #Add the cut in case it has not been added yet. if cutAdded[0]==-1: cutAdded[0] = newPolygon[0].vertexCount newPolygon[0].setVertex(newPolygon[0].vertexCount, localExitPoint) newPolygon[0].vertexCount+=1 newPolygon[0].setVertex(newPolygon[0].vertexCount, localEntryPoint) newPolygon[0].vertexCount+=1 if cutAdded[1]==-1: cutAdded[1] = newPolygon[1].vertexCount newPolygon[1].setVertex(newPolygon[1].vertexCount, localEntryPoint) newPolygon[1].vertexCount+=1 newPolygon[1].setVertex(newPolygon[1].vertexCount, localExitPoint) newPolygon[1].vertexCount+=1 # Cut based on the split size for n in range(2): if cutAdded[n] > 0: offset = newPolygon[n].getVertex(cutAdded[n]-1) - newPolygon[n].getVertex(cutAdded[n]) else: offset = newPolygon[n].getVertex(newPolygon[n].vertexCount-1) - newPolygon[n].getVertex(0) offset.Normalize() newPolygon[n].setVertex(cutAdded[n], newPolygon[n].getVertex(cutAdded[n]) + splitSize * offset) if cutAdded[n] < newPolygon[n].vertexCount-2: offset = newPolygon[n].getVertex(cutAdded[n]+2) - newPolygon[n].getVertex(cutAdded[n]+1) else: offset = newPolygon[n].getVertex(0) - newPolygon[n].getVertex(newPolygon[n].vertexCount-1) offset.Normalize() newPolygon[n].setVertex(cutAdded[n]+1, newPolygon[n].getVertex(cutAdded[n]+1) + splitSize * offset) #Check if the new shapes are not too tiny. for n in range(2): for i in range(newPolygon[n].vertexCount): for j in range(newPolygon[n].vertexCount): if i != j and (newPolygon[n].getVertex(i) - newPolygon[n].getVertex(j)).Length() < 0.1: return False # Make sure the shapes are valid before creation try: for n in range(2): box2d.b2CheckPolygonDef(newPolygon[n]) except ValueError, s: print "Created bad shape:", s return False return True def Cut(self): segmentLength = 30.0 segment=box2d.b2Segment() laserStart=(5.0-0.1,0.0) laserDir =(segmentLength,0.0) segment.p1 = self.laserBody.GetWorldPoint(laserStart) segment.p2 = segment.p1 + self.laserBody.GetWorldVector(laserDir) max_shapes = 64 count, shapes = self.world.Raycast(segment, max_shapes, False, None) for i in range(count): #Make sure it's a polygon, we cannot cut circles. if shapes[i].GetType() != box2d.e_polygonShape: continue polyShape = shapes[i].getAsType() b = polyShape.GetBody() #Custom check to make sure we don't cut stuff we don't want to cut. if b.GetUserData() != 1: continue #return if we cannot pass trough uncutable shapes. pd=[box2d.b2PolygonDef(),box2d.b2PolygonDef()] pd[0].density = 5.0 pd[1].density = 5.0 if self.SplitShape(polyShape, segment, 0.1, pd): b.DestroyShape(shapes[i]) b.CreateShape(pd[0]) b.SetMassFromShapes() b.WakeUp() bd=box2d.b2BodyDef() bd.userData = 1 bd.position = b.GetPosition() bd.angle = b.GetAngle() newBody = self.world.CreateBody(bd) newBody.CreateShape(pd[1]) newBody.SetMassFromShapes() newBody.SetAngularVelocity(b.GetAngularVelocity()) newBody.SetLinearVelocity(b.GetLinearVelocity()) def Keyboard(self, key): if key==K_c: self.Cut() def Step(self, settings): super(BoxCutter, self).Step(settings) if not self.laserBody: return self.DrawStringCR("Keys: Cut = c") segmentLength = 30.0 segment=box2d.b2Segment() laserStart=(5.0-0.1,0.0) laserDir =(segmentLength,0.0) segment.p1 = self.laserBody.GetWorldPoint(laserStart) segment.p2 = segment.p1+self.laserBody.GetWorldVector(laserDir) laserColor=box2d.b2Color(1,0,0) self.debugDraw.DrawSegment(segment.p1,segment.p2,laserColor) if __name__=="__main__": main(BoxCutter)