Get the vertices of a triangle.

( p1, p2, p3 ) =
    Triangle3d.vertices exampleTriangle


p1 ==
    Point3d ( 1, 0, 0 )


p2 ==
    Point3d ( 2, 0, 0 )


p3 ==
    Point3d ( 2, 1, 3 )

Get the edges of a triangle: from the first vertex to the second, from the second to the third, and from the third back to the first.

( e1, e2, e3 ) =
    Triangle3d.edges exampleTriangle


e1 ==
    LineSegment3d ( Point3d ( 1, 0, 0 ), Point3d ( 2, 0, 0 ) )


e2 ==
    LineSegment3d ( Point3d ( 2, 0, 0 ), Point3d ( 2, 1, 3 ) )


e3 ==
    LineSegment3d ( Point3d ( 2, 1, 3 ), Point3d ( 1, 0, 0 ) )

Get the centroid (center of mass) of a triangle.

Triangle3d.centroid exampleTriangle ==
    Point3d ( 1.6667, 0.6667, 1 )

Get the area of a triangle. This value is always positive.

Triangle3d.area exampleTriangle ==
    1.5811

Scale a triangle about a given point by a given scale.

Triangle3d.scaleAbout Point3d.origin 2 exampleTriangle ==
    Triangle3d
        ( Point3d ( 2, 0, 0 )
        , Point3d ( 4, 0, 0 )
        , Point3d ( 4, 2, 6 )
        )

Rotate a triangle around a given axis by a given angle (in radians).

Triangle3d.rotateAround Axis3d.z (degrees 90) exampleTriangle ==
    Triangle3d
        ( Point3d ( 0, 1, 0 )
        , Point3d ( 0, 2, 0 )
        , Point3d ( -1, 2, 3 )
        )

Translate a triangle by a given displacement.

displacement =
    Vector3d ( 2, -1, 3 )


Triangle3d.translateBy displacement exampleTriangle ==
    Triangle3d
        ( Point3d ( 3, -1, 3 )
        , Point3d ( 4, -1, 3 )
        , Point3d ( 4, 0, 6 )
        )

Mirror a triangle across a given plane.

Triangle3d.mirrorAcross Plane3d.yz exampleTriangle ==
    Triangle3d
        ( Point3d ( -1, 0, 0 )
        ( Point3d ( -2, 0, 0 )
        ( Point3d ( -2, 1, 3 )
        )

Project a triangle onto a given plane.

Triangle3d.projectOnto Plane3d.xy exampleTriangle ==
    Triangle3d
        ( Point3d ( 1, 0, 0 )
        , Point3d ( 2, 0, 0 )
        , Point3d ( 2, 1, 0 )
        )


Triangle3d.projectOnto Plane3d.xz exampleTriangle ==
    Triangle3d
        ( Point3d ( 1, 0, 0 )
        , Point3d ( 2, 0, 0 )
        , Point3d ( 2, 0, 3 )
        )

Transform each vertex of a triangle by a given function and create a new triangle from the resulting points. Most other transformation functions can be defined in terms of map; for example,

Triangle.projectOnto Plane3d.xz exampleTriangle ==
    Triangle.map (Point3d.projectOnto Plane3d.xz) exampleTriangle

Take a triangle defined in global coordinates, and return it expressed in local coordinates relative to a given reference frame.

localFrame =
    Frame3d.at (Point3d ( 2, 1, 3 ))


Triangle3d.relativeTo localFrame exampleTriangle ==
    Triangle3d
        ( Point3d ( -1, -1, -3 )
        , Point3d ( 0, -1, -3 )
        , Point3d ( 0, 0, 0 )
        )

Take a triangle considered to be defined in local coordinates relative to a given reference frame, and return that triangle expressed in global coordinates.

localFrame =
    Frame3d.at (Point3d ( 2, 1, 3 ))


Triangle3d.placeIn localFrame exampleTriangle ==
    Triangle3d
        ( Point3d ( 3, 1, 3 )
        , Point3d ( 4, 1, 3 )
        , Point3d ( 4, 2, 6 )
        )

Project a triangle into a given sketch plane. Conceptually, this projects the triangle onto the plane and then expresses the projected triangle in 2D sketch coordinates.

Triangle3d.projectInto SketchPlane3d.xy exampleTriangle ==
    Triangle2d
        ( Point2d ( 1, 0 )
        , Point2d ( 2, 0 )
        , Point2d ( 2, 1 )
        )


Triangle3d.projectInto SketchPlane3d.zx exampleTriangle ==
    Triangle2d
        ( Point2d ( 0, 1 )
        , Point2d ( 0, 2 )
        , Point2d ( 3, 2 )
        )

Get the minimal bounding box containing a given triangle.

Triangle3d.boundingBox exampleTriangle ==
    BoundingBox3d
        { minX = 1
        , maxX = 2
        , minY = 0
        , maxY = 1
        , minZ = 0
        , maxZ = 3
        }