3D Points instead of Beads
by Reinhard Siegel
Sometimes when designing a new boat, one can fall back on an already existing model that something may need to be modified. For example, hull master curves should be curved instead of being straight or get rid of other restrictions, so they could be more freely shaped.
The model points_instead_of_beads-0.ms2 will show how the construction of a hull form, whose master curves are essentially determined by beads, can be reconstructed by replacing these beads with free points.
Model points_instead_of_beads-0.ms2 - initial model
The hull consists of the two C-spline Lofted Surfaces topside_0 and bottom_0. Except for the bow mc, the base of the mcs are lines spanned between points which determine the top of the hull side, chine and bottom contour. On these lines are beads. For mc2 and mc3 for side and bottom, points depend on it; Together with the parents of the lines, they determine B-spline curves.
In turn, the points dependent on the beads can only be displaced to a limited extent, and only perpendicular to the respective line. User coordinate systems of the 3-point Frame type are responsible for this.
The two rear mcs for side and bottom are also B-spline Curves. Since their inner control points are just beads, they run straight.
The task is to "free" the mcs of all those the beads, in order to shape them more freely.
First, the cps p22, p24, p25 (mc2_top and mc2_bot) are selected. In the Properites Manager you can see that these points have the entry "various" in the right-hand field of the row "Frame", as well as in the row "Point". That is, their coordinates do not refer exclusively to the global coordinate system, they are not "free".
Model points_instead_of_beads-0.ms2 - the inner cps of the two mcs in the forebody depend on Beads and 3-point Frames.
To change this, click in the "Frame" row in the Properties Manager and then simply select "*" in the Entities Manager from the System entities.
Model points_instead_of_beads-0.ms2 - solving the dependence of the selected points on the 3-point frame.
Answer the following prompt with "Preserve Absolute Location".
Repeat the same steps for the row "Point" in the Properties Manager: select the System entity "*" and affirm "Preserve Absolute Location". Now all cps of the two mcs are free 3D points, only refering to the global XYZ coordinate system.
Model points_instead_of_beads-0.ms2 - the selected cps only depend on the global XYZ coordinate system.
Similarly, these steps are now repeated for the points p32, p34 and p35 of mc3_top and mc3_bot.
Since the inner cps of the two rear mcs are beads, the first thing to do is create points in their position. To do this, first select Bead e_p42 and create a new point (here pt1). The point is not free but is relative to e_p42.
Model points_instead_of_beads-0.ms2 - Point pt1 is in the same position as Bead e_p42 and depends on it.
To repeat this step for the other beads, select Point pt1 you just created and the beads,. Then use Main Menu / Insert / Copies to create the other required points in a single action.
Insert/ Copies allow similarly defined objects to be generated quickly.
Point entities at the position of the selected beads.generated by Insert/ Copies
All points created in this way are exactly at the position of the beads, but are still dependent on them. To change this, select the points, then in the Properties Manager in the "Point" row replace the "various" entry with the "*" System entity from the Entities Manager. And in a swift those points are absolute points in the global coordinate system.
Model points_instead_of_beads-0.ms2 - the selected points are made dependent on the global XYZ coordinate system.
All that remains is to define the rear mcs with these new points. There are two possibilities for this: a) Editing the mcs b) Adopt Children
Although possibility a) appears most obvious, the vertex curves vl_1 to vl_5 also depend on the beads. That is why option b) is preferable. Select a bead and the point which is in the same place, then Main Menu/ Tools/ Adopt Children:
Model points_instead_of_beads-0.ms2 - transfer the dependencies of Bead e_p42 to the Point pt1.
These steps should be repeated for all remaining beads.
Finally, the objects that are no longer needed (Lines, 3-point Frames, Beads, etc.) can be deleted to clean up the model and keep it clear.
Model points_instead_of_beads-1.ms2 - changed shape with the new free control points of the master curve
A change of form according to the current design criteria can now go on.
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