PolygonMesh

class PolygonMesh

Parent: Object	Class Index
Methods:new, add_point, add_polygon, count_points, count_polygons, normal_at, point_at, point_index, points, polygon_at, polygon_points_at, polygons, set_point, transform!, uvs, uv_at
Sample Code: polygonmeshtests.rb

The PolygonMesh class contains methods to create polygon mesh structures.

Class Methods

new

The new method is used to create a new empty polygon mesh.

Syntax:

mesh = Geom::PolygonMesh.new numpoints, numpolygons

Arguments:

Return Value:

Comments:

The number of points and polygons are optional and are just used as a hint to decide how much space to pre-allocate to speed up adding points and polygons.

Example:

mesh = Geom::PolygonMesh.new

Instance Methods

add_point

The add_point method is used to add a point to the mesh.

Syntax:

index = polygonmesh.add_point point

Arguments:

point - a Point3D object

Return Value:

index - the index in the mesh for the point

Comments:

The index can be used for creating polygons.

Example:

mesh = Geom::PolygonMesh.new
point = Geom::Point3d.new 0,1,2
index = mesh.add_point point

add_polygon

The add_polygon method is used for adding a polygon to a polygon mesh.

Syntax:

index = polygonmesh.add_polygon polygon

Arguments:

polygon - a polygon

Return Value:

index - the index of the polygon in the mesh if successful

Comments:

Example:

mesh = Geom::PolygonMesh.new
point = Geom::Point3d.new 0,1,2
point1 = Geom::Point3d.new 1,0,2
point2 = Geom::Point3d.new 2,0,1
status = mesh.add_polygon point, point1, point2

count_points

The count_points method is used to count the number of points in a mesh.

Syntax:

points = mesh.count_points

Arguments:

Return Value:

points - the number of points in a mesh, if successful

Comments:

Example:

mesh = Geom::PolygonMesh.new
point = Geom::Point3d.new 0,1,2
index = mesh.add_point point
num = mesh.count_points

count_polygons

The count_polygons count the number of polygons in the mesh.

Syntax:

polygons = mesh.count_polygons

Arguments:

Return Value:

polygons - the number of polygons in the mesh, if successful

Comments:

Example:

mesh = Geom::PolygonMesh.new
point = Geom::Point3d.new 0,1,2
point1 = Geom::Point3d.new 1,0,2
point2 = Geom::Point3d.new 2,0,1
index = mesh.add_polygon point, point1, point2
nump = mesh.count_polygons

normal_at

The normal_at method is used to determine the normal at a particular index in the mesh.

Syntax:

normal = polygonmesh.normal_at index

Arguments:

index - the index in the mesh where the normal is that you want to retrieve

Return Value:

normal - a normal

Comments:

Index is 1 based (starts at 1).

Example:

normal = mesh.normal_at 1

point_at

The point_at method is used to retrieve the point at a specific index in the mesh.

Syntax:

point = polygonmesh.point_at index

Arguments:

index - the index in the mesh where the point is that you want to retrieve

Return Value:

point - a Point3D object

Comments:

Index is 1 based (starts at 1).

Example:

mesh = Geom::PolygonMesh.new
point1 = Geom::Point3d.new 0,1,2
point2 = Geom::Point3d.new 10,20,30
index = mesh.add_point point1
index = mesh.add_point point2

point_index

The point_index method is used to retrieve the index of a point in the mesh.

Syntax:

index = polygonmesh.point_index point

Arguments:

point - a Point3d object

Return Value:

index - the index in the mesh for the Point3d object

Comments:

Returns 0 if point is not found.

Example:

mesh = Geom::PolygonMesh.new
point1 = Geom::Point3d.new 0,1,2
point2 = Geom::Point3d.new 10,20,30
index = mesh.add_point point1
index = mesh.add_point point2
index = mesh.point_index point1

points

The points method is used to retrieve an array of points (vertices) in the mesh

Syntax:

points = polygonmesh.points

Arguments:

Return Value:

points - an array of points (vertices) if successful

Comments:

Example:

mesh = Geom::PolygonMesh.new
point1 = Geom::Point3d.new 0,1,2
point2 = Geom::Point3d.new 10,20,30
index = mesh.add_point point1
index = mesh.add_point point2
# returns array of points in the mesh
num = mesh.points

polygon_at

The polygon_at method is used to retrieve an array of vertex index values for a polygon at a specific index.

Syntax:

vertices = polygonmesh.polygon_at index

Arguments:

index - the index of the desired polygon

Return Value:

vertices - an array of vertex index values

Comments:

Index is 1 based (starts at 1). The returned array can contain negative values with the sign indicating a hidden edge. For example, a return value of [-1, 2, 3] indicates that the edge from 1 to 2 is hidden. The negative values should not be used as an index for point_at, take the positive value of the index value in the polygon array. So if you get [-1, 2,3] use 1 as the arg to point_at.

Example:

mesh = Geom::PolygonMesh.new
point = Geom::Point3d.new 0,1,2
point1 = Geom::Point3d.new 1,0,2
point2 = Geom::Point3d.new 2,0,1
status = mesh.add_polygon point, point1, point2
polygon = mesh.polygon_at 1

polygon_points_at

The polygon_points_at method is used to retrieve the points for a polygon that is at a specific index in the mesh.

Syntax:

points = polygonmesh.polygon_points_at index

Arguments:

index - an index for a polygon in the mesh

Return Value:

points - an array of points that make up the polygon if successful

Comments:

Example:

polygons

The polygons method is used to retrieve an array of all polygons in the mesh.

Syntax:

polygons = polygonmesh.polygons

Arguments:

Return Value:

polygons - an array of polygons if successful

Comments:

The returned array can contain negative values with the sign indicating a hidden edge. For example, a return value of [-1, 2, 3] indicates that the edge from 1 to 2 is hidden.

Example:

mesh = Geom::PolygonMesh.new
point = Geom::Point3d.new 0,1,2
point1 = Geom::Point3d.new 1,0,2
point2 = Geom::Point3d.new 2,0,1
status = mesh.add_polygon point, point1, point2
polygons = mesh.polygons

set_point

The set_point method is used to set the point at a specific index in the mesh.

Syntax:

polygonmesh = polygonmesh.set_point index, point

Arguments:

index - the index where the point will be set

point - a Point3d object to set at the index

Return Value:

polygonmesh - a PolygonMesh object

Comments:

Example:

mesh = Geom::PolygonMesh.new
point1 = Geom::Point3d.new 0,1,2
point2 = Geom::Point3d.new 10,20,30
index = mesh.add_point point1
status = mesh.set_point 1, point2

transform!

The transform! method is used to apply a transformation to a mesh

Syntax:

polygonmesh = polygonmesh.transform! transformation

Arguments:

transformation - a Transformation object

Return Value:

polygonmesh - the PolygonMesh object

Comments:

Example:

point = Geom::Point3d.new 100,200,300
t = Geom::Transformation.new point
mesh = Geom::PolygonMesh.new
point1 = Geom::Point3d.new 0,1,2
index = mesh.add_point point1
pmesh = mesh.transform! t

uv_at

The uv_at method is used to access a uv (texture coordinates) at a specific index.

"UVs" is a way of referring to the u,v texture coordinates (as opposed to the X, Y, and Z axis that you construct your meshes on), which are points defining 1-by-1 positions within an image. These coordinates connect to points in your 3D model, to position an image texture onto it's surface (similar to virtual "thumb tacks") .

These coordinates pin an exact spot on an image that you wish to use to texture your model to a specific point on an object's surface. Between these points, your software will stretch the image smoothly. This is what is referred to as UV mapping.

Syntax:

point = polygonmesh.uv_at index

Arguments:

index - the index for the texture coordinate

Return Value:

point - a Poin3d object where the x equals the u value and the y equals the v value.

Comments:

Example:

point = mesh.uv_at(1,1)

uvs

The uvs method is used to retrieve a list of uvs.

Syntax:

uvs = polygonmesh.uvs side

Arguments:

side - a boolean. If true, use the front uvs. If false, use the back uvs.

Return Value:

uvs - an array of uvs.

Comments:

The uvs must be generated with the parameters of 1 (Include PolygonMeshUVQFront) or 2 (Include PolygonMeshUVQBack).

Example:

uvs = mesh.uvs 1