In some cases, the method "TFGBSPNode.PerformSplit" trapped into an "dead-loop" causes "stack overflow" exception. I have traced the source code and found that the method "TFGBSPNode.FindSplitPlane" always gets the same value...
unit unTest;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, GLScene, GLVectorFileObjects, GLCoordinates, GLCrossPlatform,
BaseClasses, GLWin32Viewer;
type
TForm1 = class(TForm)
GLSceneViewer1: TGLSceneViewer;
GLScene1: TGLScene;
GLCamera1: TGLCamera;
GLFreeForm1: TGLFreeForm;
GLLightSource1: TGLLightSource;
GLFreeForm2: TGLFreeForm;
procedure FormCreate(Sender: TObject);
end;
var
Form1: TForm1;
implementation
uses GLMeshCSG, GLMesh;
{$R *.dfm}
procedure TForm1.FormCreate(Sender: TObject);
var
MO: TMeshObject;
begin
GLFreeForm1.LoadFromFile('MO.glsm');
MO := TMeshObject.CreateOwned(GLFreeForm2.MeshObjects);
CSG_Operation(GLFreeForm1.MeshObjects[0], GLFreeForm1.MeshObjects[1],
CSG_Subtraction, MO, '', '');
GLFreeForm2.StructureChanged;
end;
end.
//the exception would be raised here
procedure TFGBSPNode.PerformSplit(const splitPlane : THmgPlane;
const maxTrianglesPerLeaf : Integer = MaxInt);
var
fgPos, fgNeg : TFGBSPNode;
fgPosIndices, fgNegIndices : TIntegerList;
indices : TIntegerList;
procedure SplitTriangleMid(strayID, strayNext, strayPrev : Integer;
eNext, ePrev : Single);
var
iOpp : Integer;
invSum : Single;
begin
invSum:=1/(Abs(eNext)+Abs(ePrev));
iOpp:=AddLerp(strayNext, strayPrev, Abs(eNext)*invSum, Abs(ePrev)*invSum);
if eNext>0 then begin
fgPosIndices.Add(strayID, strayNext, iOpp);
fgNegIndices.Add(iOpp, strayPrev, strayID);
end else begin
fgNegIndices.Add(strayID, strayNext, iOpp);
fgPosIndices.Add(iOpp, strayPrev, strayID);
end;
end;
procedure SplitTriangle(strayID, strayNext, strayPrev : Integer;
eStray, eNext, ePrev : Single);
var
iNext, iPrev : Integer;
invSum : Single;
begin
invSum:=1/(Abs(eNext)+Abs(eStray));
iNext:=AddLerp(strayNext, strayID, Abs(eNext)*invSum, Abs(eStray)*invSum);
invSum:=1/(Abs(ePrev)+Abs(eStray));
iPrev:=AddLerp(strayPrev, strayID, Abs(ePrev)*invSum, Abs(eStray)*invSum);
if eStray>0 then begin
fgPos.VertexIndices.Add(strayID, iNext, iPrev);
fgNeg.VertexIndices.Add(strayNext, strayPrev, iPrev);
fgNeg.VertexIndices.Add(iPrev, iNext, strayNext);
end else if eStray<0 then begin
fgNeg.VertexIndices.Add(strayID, iNext, iPrev);
fgPos.VertexIndices.Add(strayNext, strayPrev, iPrev);
fgPos.VertexIndices.Add(iPrev, iNext, strayNext);
end;
end;
var
i, i1, i2, i3, se1, se2, se3 : Integer;
e1, e2, e3 : Single;
vertices : TAffineVectorList;
subSplitPlane : THmgPlane;
begin
Assert((PositiveSubNodeIndex=0) and (NegativeSubNodeIndex=0));
ConvertToList;
// prepare sub nodes
FPositiveSubNodeIndex:=Owner.Count;
fgPos:=TFGBSPNode.CreateOwned(Owner);
fgPosIndices:=fgPos.VertexIndices;
FNegativeSubNodeIndex:=Owner.Count;
fgNeg:=TFGBSPNode.CreateOwned(Owner);
fgNegIndices:=fgNeg.VertexIndices;
// initiate split
Self.FSplitPlane:=splitPlane;
indices:=TIntegerList.Create;
vertices:=Owner.Owner.Vertices;
i:=0; while i<VertexIndices.Count do begin
// evaluate all points
i1:=VertexIndices[i];
e1:=PlaneEvaluatePoint(splitPlane, vertices.List^[i1]);
i2:=VertexIndices[i+1];
e2:=PlaneEvaluatePoint(splitPlane, vertices.List^[i2]);
i3:=VertexIndices[i+2];
e3:=PlaneEvaluatePoint(splitPlane, vertices.List^[i3]);
if Abs(e1)<cOwnTriangleEpsilon then begin
e1:=0;
se1:=0;
end else se1:=Sign(e1);
if Abs(e2)<cOwnTriangleEpsilon then begin
e2:=0;
se2:=0;
end else se2:=Sign(e2);
if Abs(e3)<cOwnTriangleEpsilon then begin
e3:=0;
se3:=0;
end else se3:=Sign(e3);
// case disjunction
case se1 of
-1 : case se2 of
-1 : case se3 of
-1, 0 : fgNegIndices.Add(i1, i2, i3);
+1 : SplitTriangle(i3, i1, i2, e3, e1, e2);
end;
0 : case se3 of
-1, 0 : fgNegIndices.Add(i1, i2, i3);
+1 : SplitTriangleMid(i2, i3, i1, e3, e1);
end;
+1 : case se3 of
-1 : SplitTriangle(i2, i3, i1, e2, e3, e1);
0 : SplitTriangleMid(i3, i1, i2, e1, e2);
+1 : SplitTriangle(i1, i2, i3, e1, e2, e3);
end;
end;
0 : case se2 of
-1 : case se3 of
-1, 0 : fgNegIndices.Add(i1, i2, i3);
+1 : SplitTriangleMid(i1, i2, i3, e2, e3);
end;
0 : case se3 of
-1 : fgNegIndices.Add(i1, i2, i3);
0 : indices.Add(i1, i2, i3);
+1 : fgPosIndices.Add(i1, i2, i3);
end;
+1 : case se3 of
-1 : SplitTriangleMid(i1, i2, i3, e2, e3);
0, +1 : fgPosIndices.Add(i1, i2, i3);
end;
end;
+1 : case se2 of
-1 : case se3 of
-1 : SplitTriangle(i1, i2, i3, e1, e2, e3);
0 : SplitTriangleMid(i3, i1, i2, e1, e2);
+1 : SplitTriangle(i2, i3, i1, e2, e3, e1);
end;
0 : case se3 of
-1 : SplitTriangleMid(i2, i3, i1, e3, e1);
0, +1 : fgPosIndices.Add(i1, i2, i3);
end;
+1 : case se3 of
-1 : SplitTriangle(i3, i1, i2, e3, e1, e2);
0, +1 : fgPosIndices.Add(i1, i2, i3);
end;
end;
end;
Inc(i, 3);
end;
VertexIndices:=indices;
indices.Free;
if fgPos.TriangleCount=0 then begin
FPositiveSubNodeIndex:=0;
FNegativeSubNodeIndex:=FNegativeSubNodeIndex-1;
FreeAndNil(fgPos);
end;
if fgNeg.TriangleCount=0 then begin
FNegativeSubNodeIndex:=0;
FreeAndNil(fgNeg);
end;
if Assigned(fgPos) and (fgPos.TriangleCount>maxTrianglesPerLeaf) then begin
subSplitPlane:=fgPos.FindSplitPlane;//in some case, "FindSplitPlane" always get the same value
fgPos.PerformSplit(subSplitPlane, maxTrianglesPerLeaf);
end;
if Assigned(fgNeg) and (fgNeg.TriangleCount>maxTrianglesPerLeaf) then begin
subSplitPlane:=fgNeg.FindSplitPlane;//in some case, "FindSplitPlane" always get the same value
fgNeg.PerformSplit(subSplitPlane, maxTrianglesPerLeaf);
end;
end;
function TFGBSPNode.FindSplitPlane(triangleSplitCost : Single = 1;
triangleImbalanceCost : Single = 0.5) : THmgPlane;
var
i, k, n : Integer;
ns, np, nn : Integer;
evalPlane : THmgPlane;
bestEval, eval : Single;
vertices : TAffineVectorList;
begin
Result:=NullHmgVector;
bestEval:=1e30;
n:=VertexIndices.Count;
vertices:=Owner.Owner.Vertices;
if n>0 then for k:=0 to n div 4 do begin
case Mode of
fgmmTriangles, fgmmFlatTriangles : begin
i:=Random((n div 3)-1)*3;
evalPlane:=PlaneMake(vertices[VertexIndices[i]],
vertices[VertexIndices[i+1]],
vertices[VertexIndices[i+2]]);
end;
fgmmTriangleStrip : begin
i:=Random(n-2);
evalPlane:=PlaneMake(vertices[VertexIndices[i]],
vertices[VertexIndices[i+1]],
vertices[VertexIndices[i+2]]);
end;
else
// fgmmTriangleFan
i:=Random(n-2);
evalPlane:=PlaneMake(vertices[VertexIndices[0]],
vertices[VertexIndices[i]],
vertices[VertexIndices[i+1]]);
end;
EvaluateSplitPlane(evalPlane, ns, np, nn);
eval:=ns*triangleSplitCost+Abs(np-nn)*0.5*triangleImbalanceCost;
if eval<bestEval then begin
bestEval:=eval;
Result:=evalPlane;
end;
end;
end;
The fallowing Data would trap "PerformSplit" into a infinite recusion. It looks like a incline.
(7009.6484375, 17768.642578, -3770.213623) (3504.8242188, 17524.121094, -3770.213623) (7009.6484375, 17768.642578, -2970.2131348)
(7009.6484375, 17768.642578, -2970.2131348) (3504.8242188, 17524.121094, -3770.213623) (3504.8242188, 17524.121094, -2970.2131348)
I have uploaded a [demo]:https://sourceforge.net/apps/phpbb/glscene/download/file.php?id=387&sid=730698aae61c17e76802714334745f04 to reproduce the problem. In the demo , the file "MO.glsm" is made up of two MeshObjects translated from TGLExtrusionSolid Object.
Thanks in advance for any suggestion.
Thanks all. The problem was solved. The Answer as follow: The function "CalcPlaneNormal" in VectorGeometry.pas returns an incorrect Normal, bcoz Vertexs value is very large as above. E.g, the normal would be "13119570882.098259961" calculated by "CalcPlaneNormal", and the rounding issue would happen here... so I translated the big coordinate value to a small coordinate value. And the exception has gone.
