support las with large coord

Author: gaoxing

src/pointcloudToLod/pointVisitor.cpp

@@ -58,6 +58,7 @@ namespace seed
 bool ReadNextPoint(PointCI& point) override;
 
 private:
+osg::Vec3d _offsetFirstPoint;
 laszip_point* _pointRead;//current reading point
 laszip_POINTER _laszipReader;
 laszip_header* _laszipHeader;
@@ -164,15 +165,21 @@ namespace seed
 // init offset
 if (_currentPointId == 0)
 {
+_offsetFirstPoint[0] = _pointRead->X * _laszipHeader->x_scale_factor;
+_offsetFirstPoint[1] = _pointRead->Y * _laszipHeader->y_scale_factor;
+_offsetFirstPoint[2] = _pointRead->Z * _laszipHeader->z_scale_factor;
+
 _offset[0] = _laszipHeader->x_offset;
 _offset[1] = _laszipHeader->y_offset;
 _offset[2] = _laszipHeader->z_offset;
+
+_offset += _offsetFirstPoint;
 }
 
 // add scale to coords
-pt.P[0] = _pointRead->X * _laszipHeader->x_scale_factor;
-pt.P[1] = _pointRead->Y * _laszipHeader->y_scale_factor;
-pt.P[2] = _pointRead->Z * _laszipHeader->z_scale_factor;
+pt.P[0] = _pointRead->X * _laszipHeader->x_scale_factor - _offsetFirstPoint[0];
+pt.P[1] = _pointRead->Y * _laszipHeader->y_scale_factor - _offsetFirstPoint[1];
+pt.P[2] = _pointRead->Z * _laszipHeader->z_scale_factor - _offsetFirstPoint[2];
 
 auto& rgb = _pointRead->rgb;
 pt.C[0] = Color8Bits(rgb[0]);