ianmackenzie/elm-geometry-prerelease/1.0.0

NOTE: the latest version is 1.0.1

BoundingBox3d

A BoundingBox3d is a rectangular box in 3D defined by its minimum and maximum X, Y and Z values. It is possible to generate bounding boxes for most geometric objects; for example, Triangle3d.boundingBox takes a Triangle3d and returns a BoundingBox3d that contains that triangle. There are several use cases where it is more efficient to deal with the bounding box of an object than the object itself, such as:

  • Intersection checking: If (for example) the bounding boxes of a line segment and a triangle do not overlap, then the line segment and triangle cannot possibly intersect each other. Expensive intersection checking therefore only has to be performed for line segments and triangles whose bounding boxes do overlap.
  • 3D rendering: When rendering a 3D scene, any object whose bounding box is not visible must itself be not visible, and therefore does not have to be drawn. This provides a simple form of culling.
type alias BoundingBox3d =
BoundingBox3d

Constructors

{ minX : Float
, maxX : Float
, minY : Float
, maxY : Float
, minZ : Float
, maxZ : Float
}
-> BoundingBox3d

Construct a bounding box from its minimum and maximum X, Y and Z values:

exampleBox =
    BoundingBox3d.fromExtrema
        { minX = -2
        , maxX = 2
        , minY = 2
        , maxY = 5
        , minZ = 3
        , maxZ = 4
        }

If the minimum and maximum values are provided in the wrong order (for example if <code>minX > maxX</code>), then they will be swapped so that the resulting bounding box is valid.

singleton : Point3d -> BoundingBox3d

Construct a zero-width bounding box containing a single point.

point =
    Point3d.fromCoordinates ( 2, 1, 3 )


BoundingBox3d.singleton point
--> BoundingBox3d.fromExtrema
-->     { minX = 2
-->     , maxX = 2
-->     , minY = 1
-->     , maxY = 1
-->     , minZ = 3
-->     , maxZ = 3
-->     }
from : Point3d -> Point3d -> BoundingBox3d

Construct a bounding box with the two given points as two of its corners. The points can be given in any order and don't have to represent the 'primary' diagonal of the bounding box.

firstPoint =
    Point3d.fromCoordinates ( 2, 1, 3 )


secondPoint =
    Point3d.fromCoordinates ( -1, 5, -2 )


BoundingBox3d.from firstPoint secondPoint
--> BoundingBox3d.fromExtrema
-->     { minX = -1
-->     , maxX = 2
-->     , minY = 1
-->     , maxY = 5
-->     , minZ = -2
-->     , maxZ = 3
-->     }
hull : BoundingBox3d -> BoundingBox3d -> BoundingBox3d

Build a bounding box that contains both given bounding boxes.

firstBox =
    BoundingBox3d.fromExtrema
        { minX = 1
        , maxX = 4
        , minY = 2
        , maxY = 3
        , minZ = 0
        , maxZ = 5
        }


secondBox =
    BoundingBox3d.fromExtrema
        { minX = -2
        , maxX = 2
        , minY = 4
        , maxY = 5
        , minZ = -1
        , maxZ = 0
        }


BoundingBox3d.hull firstBox secondBox
--> BoundingBox3d.fromExtrema
-->     { minX = -2
-->     , maxX = 4
-->     , minY = 2
-->     , maxY = 5
-->     , minZ = -1
-->     , maxZ = 5
-->     }
intersection : BoundingBox3d -> BoundingBox3d -> Maybe BoundingBox3d

Attempt to build a bounding box that contains all points common to both given bounding boxes. If the given boxes do not overlap, returns Nothing.

firstBox =
    BoundingBox3d.fromExtrema
        { minX = 1
        , maxX = 4
        , minY = 2
        , maxY = 3
        , minZ = 5
        , maxZ = 8
        }


secondBox =
    BoundingBox3d.fromExtrema
        { minX = 2
        , maxX = 5
        , minY = 1
        , maxY = 4
        , minZ = 6
        , maxZ = 7
        }


thirdBox =
    BoundingBox3d.fromExtrema
        { minX = 1
        , maxX = 4
        , minY = 4
        , maxY = 5
        , minZ = 5
        , maxZ = 8
        }


BoundingBox3d.intersection firstBox secondBox
--> Just
-->     (BoundingBox3d.fromExtrema
-->         { minX = 2
-->         , maxX = 4
-->         , minY = 2
-->         , maxY = 3
-->         , minZ = 6
-->         , maxZ = 7
-->         }
-->     )


BoundingBox3d.intersection firstBox thirdBox
--> Nothing

If two boxes just touch along an edge or at a corner, they are still considered to have an intersection, even though that intersection will have zero area (at least one of its dimensions will be zero):

firstBox =
    BoundingBox3d.fromExtrema
        { minX = 0
        , maxX = 1
        , minY = 0
        , maxY = 2
        , minZ = 0
        , maxZ = 3
        }


secondBox =
    BoundingBox3d.fromExtrema
        { minX = 1
        , maxX = 2
        , minY = 1
        , maxY = 3
        , minZ = 1
        , maxZ = 4
        }


BoundingBox3d.intersection firstBox secondBox
--> Just
-->     (BoundingBox3d.fromExtrema
-->         { minX = 1
-->         , maxX = 1
-->         , minY = 1
-->         , maxY = 2
-->         , minZ = 1
-->         , maxZ = 3
-->         }
-->     )
aggregate : List BoundingBox3d -> Maybe BoundingBox3d

Construct a bounding box containing all bounding boxes in the given list. If the list is empty, returns Nothing.

singletonBox =
    BoundingBox3d.singleton
        (Point3d.fromCoordinates ( 2, 1, 0 ))


BoundingBox3d.aggregate [ exampleBox, singletonBox ]
--> Just
-->     (BoundingBox3d.fromExtrema
-->         { minX = -2,
-->         , maxX = 2
-->         , minY = 1
-->         , maxY = 5
-->         , minZ = 0
-->         , maxZ = 4
-->         }
-->     )


BoundingBox3d.aggregate [ exampleBox ]
--> Just exampleBox


BoundingBox3d.aggregate []
--> Nothing

If you have exactly two bounding boxes, you can use BoundingBox3d.hull instead (which returns a BoundingBox3d instead of a Maybe BoundingBox3d).

containingPoints : List Point3d -> Maybe BoundingBox3d

Construct a bounding box containing all points in the given list. If the list is empty, returns Nothing.

BoundingBox3d.containingPoints
    [ Point3d.fromCoordinates ( 2, 1, 3 )
    , Point3d.fromCoordinates ( -1, 5, -2 )
    , Point3d.fromCoordinates ( 6, 4, 2 )
    ]
--> Just <|
-->     BoundingBox3d.fromExtrema
-->         { minX = -1
-->         , maxX = 6
-->         , minY = 1
-->         , maxY = 5
-->         , minZ = -2
-->         , maxZ = 3
-->         }


BoundingBox3d.containingPoints []
--> Nothing

Properties

BoundingBox3d
-> { minX : Float
, maxX : Float
, minY : Float
, maxY : Float
, minZ : Float
, maxZ : Float
}

Get the minimum and maximum X, Y and Z values of a bounding box in a single record.

BoundingBox3d.extrema exampleBox
--> { minX = -2
--> , maxX = 2
--> , minY = 2
--> , maxY = 5
--> , minZ = 3
--> , maxZ = 4
--> }

Can be useful when combined with record destructuring, for example

{ minX, maxX, minY, maxY, minZ, maxZ } =
    BoundingBox3d.extrema exampleBox




--> minX = -2
--> maxX = 2
--> minY = 2
--> maxY = 5
--> minZ = 3
--> maxZ = 4
minX : BoundingBox3d -> Float

Get the minimum X value of a bounding box.

BoundingBox3d.minX exampleBox
--> -2
maxX : BoundingBox3d -> Float

Get the maximum X value of a bounding box.

BoundingBox3d.maxX exampleBox
--> 2
minY : BoundingBox3d -> Float

Get the minimum Y value of a bounding box.

BoundingBox3d.minY exampleBox
--> 2
maxY : BoundingBox3d -> Float

Get the maximum Y value of a bounding box.

BoundingBox3d.maxY exampleBox
--> 5
minZ : BoundingBox3d -> Float

Get the minimum Z value of a bounding box.

BoundingBox3d.minZ exampleBox
--> 3
maxZ : BoundingBox3d -> Float

Get the maximum Z value of a bounding box.

BoundingBox3d.maxZ exampleBox
--> 4
dimensions : BoundingBox3d -> ( Float, Float, Float )

Get the X, Y and Z dimensions (widths) of a bounding box.

BoundingBox3d.dimensions exampleBox
--> ( 4, 3, 1 )
midX : BoundingBox3d -> Float

Get the median X value of a bounding box.

BoundingBox3d.midX exampleBox
--> 0
midY : BoundingBox3d -> Float

Get the median Y value of a bounding box.

BoundingBox3d.midY exampleBox
--> 3.5
midZ : BoundingBox3d -> Float

Get the median Z value of a bounding box.

BoundingBox3d.midZ exampleBox
--> 3.5
centerPoint : BoundingBox3d -> Point3d

Get the point at the center of a bounding box.

BoundingBox3d.centerPoint exampleBox
--> Point3d.fromCoordinates ( 0, 3.5, 3.5 )
centroid : BoundingBox3d -> Point3d

DEPRECATED: Alias for centerPoint, will be removed in the next major release. Use centerPoint instead.

Queries

contains : Point3d -> BoundingBox3d -> Bool

Check if a bounding box contains a particular point.

firstPoint =
    Point3d.fromCoordinates ( 1, 4, 3 )


secondPoint =
    Point3d.fromCoordinates ( 3, 4, 5 )


BoundingBox3d.contains firstPoint exampleBox
--> True


BoundingBox3d.contains secondPoint exampleBox
--> False
isContainedIn : BoundingBox3d -> BoundingBox3d -> Bool

Test if the second given bounding box is fully contained within the first (is a subset of it).

outerBox =
    BoundingBox3d.fromExtrema
        { minX = 0
        , maxX = 10
        , minY = 0
        , maxY = 10
        , minZ = 0
        , maxZ = 10
        }


innerBox =
    BoundingBox3d.fromExtrema
        { minX = 1
        , maxX = 5
        , minY = 3
        , maxY = 9
        , minZ = 7
        , maxZ = 8
        }


overlappingBox =
    BoundingBox3d.fromExtrema
        { minX = 1
        , maxX = 5
        , minY = 3
        , maxY = 12
        , minZ = 7
        , maxZ = 8
        }


BoundingBox3d.isContainedIn outerBox innerBox
--> True


BoundingBox3d.isContainedIn outerBox overlappingBox
--> False
intersects : BoundingBox3d -> BoundingBox3d -> Bool

Test if two boxes touch or overlap at all (have any points in common);

BoundingBox3d.intersects firstBox secondBox

is equivalent to

BoundingBox3d.intersection firstBox secondBox
    /= Nothing

but is more efficient.

firstBox =
    BoundingBox3d.fromExtrema
        { minX = 0
        , maxX = 3
        , minY = 0
        , maxY = 2
        , minZ = 0
        , maxZ = 1
        }


secondBox =
    BoundingBox3d.fromExtrema
        { minX = 0
        , maxX = 3
        , minY = 1
        , maxY = 4
        , minZ = -1
        , maxZ = 2
        }


thirdBox =
    BoundingBox3d.fromExtrema
        { minX = 0
        , maxX = 3
        , minY = 4
        , maxY = 5
        , minZ = -1
        , maxZ = 2
        }


BoundingBox3d.intersects firstBox secondBox
--> True


BoundingBox3d.intersects firstBox thirdBox
--> False
overlappingBy : Order -> Float -> BoundingBox3d -> BoundingBox3d -> Bool

Check if one box overlaps another by less than, greater than or equal to a given amount. For example, you could implement a tolerant collision check (one that only returns true if the boxes overlap by at least some small finite amount, and ignores boxes that just barely touch each other) as

boxesCollide box1 box2 =
    BoundingBox3d.overlappingBy GT 0.001 box1 box2

This can be read as "box1 and box2 are overlapping by greater than 0.001 units". (The Order type and its three values LT, GT and EQ are defined in Elm's Basics module so are available by default in any Elm program.)

Overlap is defined as the minimum distance one box would have to move so that it did not touch the other, and is always positive for any two overlapping boxes.

Boxes that just touch are considered to have an overlap of zero, which is distinct from 'no overlap'. Boxes that do not touch or overlap at all are considered to have an overlap which is less than zero but not comparable to any negative number.

Less than

  • overlappingBy LT 1e-3 will return true if the two boxes overlap by less than 0.001 units or if they do not overlap at all (false if they overlap by more than 0.001 units).
  • overlappingBy LT 0 will return true only if the two boxes don't touch or overlap at all.
  • overlappingBy LT -1e-3 will always return false! If you care about how much two boxes are separated by, use separatedBy instead.

Greater than

  • overlappingBy GT 1e-3 will return true if the two boxes overlap by at least 0.001 units (false if they overlap by less than that or do not overlap at all).
  • overlappingBy GT 0 will return true if the two boxes overlap by any non-zero amount (false if they just touch or do not overlap at all).
  • overlappingBy GT -1e-3 doesn't make a lot of sense but will return true if the boxes touch or overlap at all (false if they don't overlap, regardless of how close they are to overlapping). In this case, though, it would make more sense to just user intersects instead.

Equal to

Checking whether two boxes overlap by exactly a given amount is pretty weird and vulnerable to floating-point roundoff, but is defined as follows:

  • overlappingBy EQ 1e-3 will return true if the two boxes overlap by exactly 0.001 units.
  • overlappingBy EQ 0 will return true if and only if the boxes just touch each other.
  • overlappingBy EQ -1e-3 will always return false.
separatedBy : Order -> Float -> BoundingBox3d -> BoundingBox3d -> Bool

Check if one box is separated from another by less than, greater than or equal to a given amount. For example, to perform clash detection between some objects, you could use separatedBy on those objects' bounding boxes as a quick check to see if the objects had a gap of at least 1 cm between them:

safelySeparated box1 box2 =
    BoundingBox3d.separatedBy GT 0.01 box1 box2

This can be read as "box1 and box2 are separated by greater than 0.01 units". (The Order type and its three values LT, GT and EQ are defined in Elm's Basics module so are available by default in any Elm program.)

Separation is defined as the minimum distance one box would have to move so that it touched the other, and is always positive for any two boxes that do not touch.

Boxes that just touch are considered to have a separation of zero, which is distinct from 'no separation'. 'No separation' (overlap) is considered to be less than zero but not comparable to any negative number.

Less than

  • separatedBy LT 1e-3 will return true if the two boxes are separated by less than 0.001 units or if they touch or overlap (false if they are separated by at least 0.001 units).
  • separatedBy LT 0 will return true only if the boxes overlap by some non-zero amount.
  • separatedBy LT -1e-3 will always return false! If you care about how much two boxes overlap by, use overlappingBy instead.

Greater than

  • separatedBy GT 1e-3 will return true if the two boxes are separated by at least 0.001 units (false if they are separated by less than that or if they touch or overlap).
  • separatedBy GT 0 will return true if the two boxes are separated by any non-zero amount (false if they touch or overlap).
  • separatedBy GT -1e-3 doesn't make a lot of sense but will return true if the boxes just touch or are separated by any amount (false if they overlap by any non-zero amount).

Equal to

Checking whether two boxes are separated by exactly a given amount is pretty weird and vulnerable to floating-point roundoff, but is defined as follows:

  • separatedBy EQ 1e-3 will return true if the two boxes are separated by exactly 0.001 units.
  • separatedBy EQ 0 will return true if and only if the boxes just touch each other.
  • separatedBy EQ -3 will always return false.

Transformations

scaleAbout : Point3d -> Float -> BoundingBox3d -> BoundingBox3d

Scale a bounding box about a given point by a given scale.

point =
    Point3d.fromCoordinates ( 2, 2, 2 )


BoundingBox3d.scaleAbout point 2 exampleBox
--> BoundingBox3d.fromExtrema
-->     { minX = -6
-->     , maxX = 2
-->     , minY = 2
-->     , maxY = 8
-->     , minZ = 4
-->     , maxZ = 6
-->     }
translateBy : Vector3d -> BoundingBox3d -> BoundingBox3d

Translate a bounding box by a given displacement.

displacement =
    Vector3d.fromComponents ( 2, -3, 1 )


BoundingBox3d.translateBy displacement exampleBox
--> BoundingBox3d.fromExtrema
-->     { minX = 0
-->     , maxX = 4
-->     , minY = -1
-->     , maxY = 2
-->     , minZ = 4
-->     , maxZ = 5
-->     }
translateIn : Direction3d -> Float -> BoundingBox3d -> BoundingBox3d

Translate a bounding box in a given direction by a given distance;

BoundingBox3d.translateIn direction distance

is equivalent to

BoundingBox3d.translateBy
    (Vector3d.withLength distance direction)