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This task will show you how to
create a network of constrained curves to be used
in the surfaces network command.On a first
step, you have created characteristic curves on the cloud.
These curves are often approximate and require some preparation: |
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- Slicing that cuts curves or edges in several pieces, according to a
pseudo-intersection:
there is a pseudo-intersection between two curves if they intersect each
other in the view direction
(but not really), and if the mini 3D distance between them at this cutting
point is lower than
the parameter
Max. Distance.
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- Deburring to remove undesirable small curve pieces, based on a
Min length
criterion.
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Then, you can create a network
from these cleaned curves according to the following:
- A network is a set of closed and connected contours, named wires,
- a contour is a set of connected edges, it is necessarily closed but
not limited to 3 or 4 sides,
- an edge belongs to one contour (free border edge) or 2 contours
(common edge),
- if there are no free border edges, the network is closed,
- a node is the topological encounter point of two or more edges.
These edges may belong to different contours.
Once the action has detected the topology (node, contours, free border
edges),
the curves are adapted to the network internal constraints such as:
- Connection constraints on nodes
(all edges ending on a common node must be connected on this point).
- Tangency constraints between two edges on a node.
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Open the
SurfNetwork.CATPart from the
samples directory. |
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Click Curves
Network
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The dialog box is displayed.
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It consists of 4 tab pages:
Stay in the Preparation
tab and select the curves to clean. They are displayed in the dialog box.
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You can:
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Select the mesh as the
Support. Click
Apply.
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Click Deleting wire to activate
the wire selection. The large wire is highlighted
and a Delete wire
button becomes available.
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Click Delete wire button to remove
this wire.
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In the cases where you want to create a surface on a
network of curves with a hole in it,
i.e. without filling one or several wires, use the Deleting wire
button to activate the wire selection,
select the wire by picking two of its edges, and Click Delete wire.
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If you do not remove the large wire, an information
message is displayed as you Click OK.
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Go to the
Constraints tab to
define constraints. The existing constraints are highlighted,
as a green dot for continuity constraints on nodes, as a blue line for
tangency constraints,
as a red curve for frozen curves.
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The
Node tolerance
defines the maximum distance between edges extremities to consider
these edges connected on a node.
You can modify this value, but it cannot be smaller than the Max
distance parameter.
The Node tolerance is visualized as a green sphere whose radius
is equal to the Node tolerance.
The size of this sphere is updated when you modify the Node tolerance
value.
You can move the sphere using the cursor.
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Tangency constraints are activated by the
Automatic tangency
select box.
You can edit the value of the tangency angle. Click Apply after
each modification.
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Select
Projection on support
to compute the network from the projections of the curves on the mesh.
The curves projected are smoothed, with the
Smoothing tolerance.
This parameter can be edited.
It is applied to all curves.
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You can choose between a global or a local
deformation constraint
(available for all deformable edges).
This constraint is applied during the geometric adaptation step.
If the Global deformation select box is set, edges deformations
are done along the entire length
of the edges.
Example of global deformation: |
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Example of local deformation: |
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Click
Default constraints to revert to the default constraints. |
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Go to the
Freeze tab page to select curves that must remain frozen.
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Pick a curve to freeze it. It is displayed in
red in the graphic area and displayed in the dialog box.
Pick it again or use the contextual menu Remove to free it.
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You can freeze only curves that have been selected
in the preparation tab.
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An edge of a face is automatically and definitely
frozen.
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Free border edges are frozen by default but you can
free them.
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The action provides a constraint solver to search
conflicts between constraints.
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A message is displayed at the end of the search.
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When all constraints have been selected, conflicts
are highlighted in magenta.
- Modify the constraints to solve the existing conflicts before
creating the wires.
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If necessary, go to the
Display tab page to
visualize defects or gaps on the curves.
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Select Distances at nodes to
display the minimum 3D distance between two curves at
their pseudo-intersection.
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They are displayed in yellow with the exception of the greatest
minimum distance found
that is displayed in black.
Click this black label to update the
Max distance in the
Preparation tab with a value
that will take all curves pseudo-intersection into account. |
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Select Spikes to display deviation
or curvatures spikes:
- Click
to display the deviation spikes between the network curves
and the input curves,
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- Click
to display the deviation spikes between the network curves
and the support mesh,
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- Click
to display the curvature spikes on the network curves.
Spikes within the tolerance are displayed in green,
spikes exceeding the tolerance are displayed in red.
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Use the Spikes scale slider to
define the size of the spikes
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and the Spikes density slider to
define their density:
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Select Max deviation and:
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You can combine Spikes and Max deviation.
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When Max deviation alone is selected, the
greatest corresponding spike is displayed.
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The Max deviation is not relevant for the
curvature .
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Although this is possible, we recommend that you do not
combine Max deviation
with Distances at nodes as it would be difficult to read the
combined information.
You should select these check boxes in turn.
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Click OK to validate the network and exit the
dialog box.
A CurvesNetwork element is created in the specification tree.
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