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Module: Geom

Overview

Note:

Lines and Planes are infinite.

The Geom module defines a number of Module methods that let you perform different geometric operations.

The methods in this module take lines and planes as arguments. There is no special class for representing lines or planes. Arrays are used for both.

A line can be represented as either an ::Array of a point and a vector, or as an ::Array of two points.

line1 = [Geom::Point3d.new(0, 0, 0), Geom::Vector3d.new(0, 0, 1)]
line2 = [Geom::Point3d.new(0, 0, 0), Geom::Point3d.new(0, 0, 100)]

A plane can be represented as either an ::Array of a point and a vector, or as an ::Array of 4 numbers that give the coefficients of a plane equation.

plane1 = [Geom::Point3d.new(0, 0, 0), Geom::Vector3d.new(0, 0, 1)]
plane2 = [0, 0, 1, 0]

There are several good books on 3D math if you are new to the concepts of a line, plane, and vector.

Version:

  • SketchUp 6.0

Class Method Summary

Class Method Details

.closest_points(line1, line2) ⇒ Array(Geom::Point3d, Geom::Point3d)

The .closest_points method is used to compute the closest points on two lines.

line.

Examples:

line1 = [Geom::Point3d.new(0, 2, 0), Geom::Vector3d.new(1, 0, 0)]
line2 = [Geom::Point3d.new(3, 0, 0), Geom::Vector3d.new(0, 1, 0)]
# This will return a point Point3d(3, 2, 0).
points = Geom.closest_points(line1, line2)

Parameters:

Returns:

Version:

  • SketchUp 6.0

.fit_plane_to_points(point1, point2, point3, ...) ⇒ Array(Geom::Point3d, Geom::Vector3d) .fit_plane_to_points(points) ⇒ Array(Geom::Point3d, Geom::Vector3d)

The .fit_plane_to_points method is used to compute a plane that is a best fit to an array of points. If more than three points are given some of the points may not be on the plane.

The plane is returned as an ::Array of 4 numbers which are the coefficients of the plane equation Ax + By + Cz + D = 0.

Examples:

point1 = Geom::Point3d.new(0, 0, 0)
point2 = Geom::Point3d.new(10, 10, 10)
point3 = Geom::Point3d.new(25, 25, 25)
plane = Geom.fit_plane_to_points(point1, point2, point3)

Overloads:

Version:

  • SketchUp 6.0

.intersect_line_line(line1, line2) ⇒ Geom::Point3d?

The .intersect_line_line computes the intersection of two lines.

Examples:

# Defines a line parallel to the Y axis, offset 20 units.
line1 = [Geom::Point3d.new(20, 0, 0), Geom::Vector3d.new(0, 1, 0)]
# Defines a line parallel to the X axis, offset 10 units.
line2 = [Geom::Point3d.new(0, 10, 0), Geom::Point3d.new(20, 10, 0)]
# This will return a point Point3d(20, 10, 0).
point = Geom.intersect_line_line(line1, line2)

Parameters:

Returns:

  • (Geom::Point3d, nil) —

    The intersection point. Returns nil if they do not intersect.

See Also:

  • Geom

Version:

  • SketchUp 6.0

.intersect_line_plane(line, plane) ⇒ Geom::Point3d?

The .intersect_line_plane method is used to compute the intersection of a line and a plane.

Examples:

# Defines a line parallel to the X axis, offset 20 units.
line = [Geom::Point3d.new(-10, 20, 0), Geom::Vector3d.new(1, 0, 0)]
# Defines a plane with it's normal parallel to the x axis.
plane = [Geom::Point3d.new(10, 0 ,0), Geom::Vector3d.new(1, 0, 0)]
# This will return a point Point3d(10, 20, 0).
point = Geom.intersect_line_plane(line, plane)

Parameters:

Returns:

  • (Geom::Point3d, nil) —

    A Point3d object. Returns nil if they do not intersect.

See Also:

  • Geom

Version:

  • SketchUp 6.0

.intersect_plane_plane(plane1, plane2) ⇒ Array(Geom::Point3d, Geom::Vector3d)

The .intersect_plane_plane method is used to compute the intersection of two planes.

Examples:

# Defines a plane with it's normal parallel to the x axis.
plane1 = [Geom::Point3d.new(10, 0 ,0), Geom::Vector3d.new(1, 0, 0)]
# Defines a plane with it's normal parallel to the y axis.
plane2 = [Geom::Point3d.new(0, 20 ,0), Geom::Vector3d.new(0, 1, 0)]
# This will return a line [Point3d(10, 20, 0), Vector3d(0, 0, 1)].
line = Geom.intersect_plane_plane(plane1, plane2)

Parameters:

Returns:

Version:

  • SketchUp 6.0

.linear_combination(weight1, point1, weight2, point2) ⇒ Geom::Point3d .linear_combination(weight1, vector1, weight2, vector2) ⇒ Geom::Vector3d

The .linear_combination method is used to compute the linear combination of points or vectors.

A linear combination is a standard term for vector math. It is defined as vector = weight1 * vector1 + weight2 * vector2.

Examples:

point1 = Geom::Point3d.new(1, 1, 1)
point2 = Geom::Point3d.new(10, 10, 10)
# Gets the point on the line segment connecting point1 and point2 that is
# 3/4 the way from point1 to point2: Point3d(7.75, 7.75, 7.75).
point = Geom.linear_combination(0.25, point1, 0.75, point2)

Overloads:

Version:

  • SketchUp 6.0

.point_in_polygon_2D(point, polygon, check_border) ⇒ Boolean

The .point_in_polygon_2D method is used to determine whether a point is inside a polygon. The z component of both the point you’re checking and the points in the polygon are ignored, effectively making it a 2-d check.

Examples:

# Create a point that we want to check. (Note that the 3rd coordinate,
# the z, is ignored for purposes of the check.)
point = Geom::Point3d.new(5, 0, 10)

# Create a series of points of a triangle we want to check against.
triangle = []
triangle << Geom::Point3d.new(0, 0, 0)
triangle << Geom::Point3d.new(10, 0, 0)
triangle << Geom::Point3d.new(0, 10, 0)

# Test to see if our point is inside the triangle, counting hits on
# the border as an intersection in this case.
hits_on_border_count = true
status = Geom.point_in_polygon_2D(point, triangle, hits_on_border_count)

Parameters:

  • point (Geom::Point3d)
  • polygon (Array<Geom::Point3d>) —

    An array of points that represent the corners of the polygon you are checking against.

  • check_border (Boolean) —

    Pass true if a point on the border should be counted as inside the polygon.

Returns:

  • (Boolean) —

    true if the point is inside the polygon.

Version:

  • SketchUp 6.0

.tesselate(polygon_loop_points, *inner_loop_points) ⇒ Array<Geom::Point3d>

Note:

The winding order of the polygons matter. The outer loop should be in counter-clockwise order. To cut an empty hole the inner loops should be in clockwise order, otherwise they will create a loop filled with triangles.

Note:

The tesselation is using the same logic as SketchUp its rendering pipeline. But the exact result is an implementation detail which may change between versions. In particularly the results of degenerate polygons and non-planar polygons is undefined as part of the API contract. Such polygons are for example polygons where all points are colinear, polygons with duplicate points, non-planar polygons.

Note:

If you want the triangles from an existing ::Sketchup::Face it’s better to use Sketchup::Face#mesh.

Tessellates a polygon, represented as a collection of 3D points. Can include holes by providing collections of points describing the inner loops. This is intended to be used for planar polygons.

Useful to draw concave polygons using Sketchup::View#draw or Sketchup::View#draw2d.

It can also be useful for importers where the input format describes only the loops for a polygon and you want to work with a collection of triangles.

Polygon with two holes, one empty and one filled:

(See “Drawing a polygon with holes from a custom tool” example)

Examples:

Iterate over each triangle in the returned set

polygon = [
  Geom::Point3d.new(0, 0, 0),
  Geom::Point3d.new(90, 0, 0),
  Geom::Point3d.new(60, 40, 0),
  Geom::Point3d.new(90, 90, 0),
  Geom::Point3d.new(30, 70, 0),
]
triangles = Geom.tesselate(polygon)
triangles.each_slice(3) { |triangle|
  # Work with each triangle set...
}
# Or get an array of triangles:
triangles_set = triangles.each_slice(3).to_a

Drawing a polygon with holes from a custom tool

class ExampleTool

  def initialize
    polygon = [
      Geom::Point3d.new(0, 0, 0),
      Geom::Point3d.new(90, 0, 0),
      Geom::Point3d.new(60, 40, 0),
      Geom::Point3d.new(90, 90, 0),
      Geom::Point3d.new(30, 70, 0),
    ] # Counter-clockwise order
    hole1 = [
      Geom::Point3d.new(20, 10, 0),
      Geom::Point3d.new(40, 10, 0),
      Geom::Point3d.new(45, 25, 0),
      Geom::Point3d.new(30, 20, 0),
      Geom::Point3d.new(25, 25, 0),
    ].reverse # Clockwise order - empty hole
    hole2 = [
      Geom::Point3d.new(30, 40, 0),
      Geom::Point3d.new(50, 40, 0),
      Geom::Point3d.new(50, 50, 0),
      Geom::Point3d.new(30, 50, 0),
    ].reverse # Counter-clockwise order - filled hole
    @triangles = Geom.tesselate(polygon, hole1, hole2)
  end

  def activate
    Sketchup.active_model.active_view.invalidate
  end

  def onMouseMove(flags, x, y, view)
    view.invalidate
  end

  def getExtents
    bounds = Geom::BoundingBox.new
    bounds.add(@triangles)
    bounds
  end

  def draw(view)
    view.drawing_color = Sketchup::Color.new(192, 0, 0)
    view.draw(GL_TRIANGLES, @triangles)
  end

end

Sketchup.active_model.select_tool(ExampleTool.new)

Parameters:

Returns:

  • (Array<Geom::Point3d>) —

    an array of points with a stride of three representing a set of triangles.

Raises:

  • (ArgumentError) —

    if any of the loops contain less than three points.

  • (RuntimeError) —

    if the tesselator returned an error.

See Also:

Version:

  • SketchUp 2020.0