Hi all,

for your reference, here's my current solution to the problem. Can anyone do it better (shorter/faster/nicer and I mean not by removing the comments :-) ?

Qt Code: 
  1. Qt3DCore::QEntity * createTransformedPlane(Qt3DCore::QEntity * parent, QVector3D p0, QVector3D p1, QVector3D p3) {
  2.  
  3. 	// vectors that span the plane
  4. 	QVector3D v1 = p1-p0;
  5. 	QVector3D v2 = p3-p0;
  6.  
  7. 	// create standard mesh in xz plane
  8. 	Qt3DExtras::QPlaneMesh *planeMesh = new Qt3DExtras::QPlaneMesh();
  9. 	float wx = v1.length();
  10. 	float wz = v2.length();
  11. 	planeMesh->setWidth(wx);
  12. 	planeMesh->setHeight(wz);
  13.  
  14. 	// Plane entity
  15. 	Qt3DCore::QEntity * planeEntity = new Qt3DCore::QEntity(parent);
  16. 	// add the mesh to the entity
  17. 	planeEntity->addComponent(planeMesh);
  18.  
  19.  
  20. 	// transformation
  21.  
  22. 	// compute normal vector
  23. 	QVector3D n1 = QVector3D::crossProduct(v1,v2);
  24.  
  25. 	// determine rotation matrix to align normal vector of plane with normal vector of generated plane (i.e. y-axis)
  26. 	QVector3D n2(0,1,0);
  27.  
  28. 	QQuaternion rot = QQuaternion::rotationTo(n2, n1);
  29.  
  30. 	// now we transform the w1 vector (corresponding to the v1 vector) into the target plane
  31. 	QVector3D w1(-1,0,0);
  32. 	// Mind: PlaneMesh is generated in x-z plane, with bottom-left point at q0=(w/2, 0, -h/2)
  33. 	//       If numbered counter clock-wise, the next point is at q1=(-w/2, 0, -h/2) and the normalized vector w1 between q0 and q1
  34. 	//       is w1=(-1,0,0)
  35.  
  36. 	QVector3D w1Rotated = rot.rotatedVector(w1);
  37.  
  38. 	// now we need to compute the rotation matrix to align the w1 vector with the v1 vector
  39. 	QQuaternion rot2 = QQuaternion::rotationTo(w1Rotated, v1);
  40.  
  41. 	// combine both rotations (mind the matrix multiplication order!)
  42. 	QQuaternion planeRotation = rot2*rot;
  43.  
  44. 	// anchor point of generated mesh
  45. 	QVector3D q0(wx/2, 0, -wz/2);
  46. 	// Point q0 after rotation
  47. 	QVector3D q0rot = planeRotation.rotatedVector(q0);
  48.  
  49. 	//translation to target anchor point
  50. 	QVector3D transVec = p0 - q0rot;
  51.  
  52. 	// create transformation
  53. 	Qt3DCore::QTransform *transform = new Qt3DCore::QTransform();
  54. 	transform->setTranslation(transVec);
  55. 	transform->setRotation(planeRotation);
  56.  
  57. 	// and set it as component
  58. 	planeEntity->addComponent(transform);
  59.  
  60. 	return planeEntity;
  61. }
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