CODEWITHSUNDEEP
delphiglscene
user3640423
user3640423

Reputation: 11

GLScene FreeForm RayCastIntersect Problems

I am using the GLScene RayCastIntersect function with Delphi (XE2) to determine the intersect point between a segment of a ballistic trajectory and a FreeForm mesh. If I import the mesh and use the RayCastIntersect function then the intersection point is reported correctly. However, if I translate the FreeForm object to a positive x coordinate then the function ceases to return the correct intersection point. The returned intersection point is always in front on the target (i.e. before the correct point of impact, around x = 0). Providing that the FreeForm is at x <= 0 then all other transformations and rotations appear to be handled correctly by the RayCastIntersect function.

I have noticed that if I perform the x transformation on individual MeshObjects of the FreeForm then the RayCastIntersection function returns the correct intersection point even for positive x translations. Unfortunately I am unable to use this as a workaround since there is not a method to rotate individual mesh objects.

Has anyone else come across this issue? Is it a known bug (although I have found nothing online about it)? Or am I doing something wrong? Any suggestions would be gratefully appreciated. See below for my Check Impact code.

function ChkImpact(Mesh: TGLFreeForm; x1, x2, y1, y2, z1, z2: Double): Boolean;
var
    rStrt, rVect, rEnd: TVector;
    dx, dy, dz: Double;
    iPoint, iNorm: TVector;
begin
      //***Check trajectory secgment intersection with target mesh***//
      rStrt := VectorMake(x1,y1,z1,0);
      rEnd := VectorMake(x2,y2,z2,0);

      dx := x2-x1;
      dy := y2-y1;
      dz := z2-z1;
      rVect := VectorMake(dx,dy,dz,1);

      if Mesh.{Octree}RayCastIntersect(rStrt, rVect, @iPoint, @iNorm) then
      begin
            iPtX := iPoint.X;
            iPtY := iPoint.Y;
            iPtZ := iPoint.Z;

            Result := PointOnSegment(iPoint, rStrt, rEnd);
      end
      else Result := False;
end;

function PointOnSegment(P, P1, P2: TVector): Boolean;
begin
      //***Check whether impact point is on the trajectory segment***//
      if ((P.X >= P1.X) and (P.X <= P2.X)) then Result := True else Result := False;
end;

Upvotes: 1

Views: 748

Answers (1)

xaid
xaid

Reputation: 750

Make sure that the Z-scale of the object that you want to do "RayCastIntersect" is not the value of 0 (zero).

This cause be a lot of trouble as well.

I used "RayCastIntersect" on a plane and the plane had the scale.z set to 0 which cause "RayCastIntersect" to return incorrect values.

I don't know why this is happening.

Upvotes: 0

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