Metafor

ULiege - Aerospace & Mechanical Engineering

User Tools

Site Tools


doc:user:geometry:user:surfaces

This is an old revision of the document!




Surfaces

Definition

In Metafor, a Surface is used to build a (Side) limited by a Wire.

The surface orientation, defined by its normal, is important in 3D contact.

Plane

A plane is defined by three points:

plane = surfaceset.add( Plane(number, p1, p2, p3) )

Its normal (and therefore the surface orientation) is calculated using the cross product of vectors $\boldsymbol{p_2}-\boldsymbol{p_1}$ et $\boldsymbol{p_3}-\boldsymbol{p_1}$.

p1, p2, p3 3 Points lying on the plane

Coons

A Coons' surface is a linear interpolation between four Curves. These Curves are gathered in a closed Wire. The Wire orientation defines the surface orientation.

coons = surfaceset.add( Coons(number, wire) )
wire the Wire which is interpolated

Ruled Surface

A ruled surface is defined by linearly interpolating two curves. The orientation of these curves sets the surface orientation.

ruled = surfaceset.add( Ruled(number, curve1, curve2) )
curve1, curve2, … the 2 Curves

Ruled surfaces can be used to create planes, if the two Curves are coplanar Lines, or cylinders if the curves are Arcs.

NURBS

nur = surfaceset.add( NurbsSurface(number) )
nur.setDegreeU(degU) 	 
nur.setDegreeV(degV) 	 
nur.push(i1,j1,p1); nur.pushWeight(i1,j1,w1) 
nur.push(i2, j2, p2); nur.pushWeight(i2, j2, w2) 	 
nur.pushKnotU(knotu1)
...
nur.pushKnotU(knotu2) 	 
nur.pushKnotV(knotv1)
...
nur.pushKnotV(knotv2) 	
degU, degV degree along U and V
i1, j1, i2, j2, … indices of the pole matrix
p1, p2, … points (called “poles”)
w1, w2, … weights
knotu1, knotu2, … knot vector along U
knotv1, knotv2, … knot vector along V

Surface of revolution

revsur = surfaceset.add( RevolutionSurface(number, axe, wire) )

where

axe Line which defines the revolution axis
wire Wire which will rotate along the revolution axis (it cannot intersect the axis on its first point and must be coplanar with it).

Cylinder

c = Cylinder(number, axis, radius, ptGen) # First way to use Cylinder

c = Cylinder(number, axis, radius)        # Second way to use Cylinder
c.setProjType(projType)

where

axis Line which defines the cylinder axis
radius cylinder radius
ptGen optional Point of the generating line of the cylinder. This point must be situated:
- in a plane perpendicular to the axis including the first point of the axis,
- to a distance equal to the cylinder radius of the first point of the axis.
Since this point is quite difficult to define when the cylinder is not parallel to an axis, a random point can be supplied and Metafor will put it in its right place with a WARNING_MESSAGE (see apps.qs.contactCylProj0Point). This point is compulsory if the cylinder has a given rotation.
projType = 0 : the surface is finite and limited by the length of the axis
= 1 : the surface is infinite
doc/user/geometry/user/surfaces.1420646912.txt.gz · Last modified: 2016/03/30 15:22 (external edit)

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki