elm-3d-camera

This package provides convenient ways to define and use perspective and orthographic cameras in 3D. It is based on elm-geometry and has two main goals:

• Provide a way to construct WebGL model/view/projection matrices that is more intuitive than using elm-explorations/linear-algebra directly
• Provide standalone 3D-to-2D projection functionality that can be used outside of WebGL

Defining cameras

To define a camera, you first create a viewpoint which represents the position and orientation of the camera:

import Viewpoint3d
import Point3d
import Direction3d

cameraViewpoint =
    Viewpoint3d.lookAt
        { eyePoint = Point3d.meters 10 0 5
        , focalPoint = Point3d.origin
        , upDirection = Direction3d.positiveZ
        }

You can then create either a perspective or orthographic camera from the viewpoint:

import Camera3d
import Angle
import Length

perspectiveCamera =
    Camera3d.perspective
        { viewpoint = cameraViewpoint
        , verticalFieldOfView = Angle.degrees 30
        }

orthographicCamera =
    Camera3d.orthographic
        { viewpoint = cameraViewpoint
        , viewportHeight = Length.meters 5
        }

WebGL rendering

Once you have a camera, you can use it to get WebGL view and projection matrices:

import WebGL.Matrices as WebGL

viewMatrix =
    WebGL.viewMatrix camera

projectionMatrix =
    WebGL.projectionMatrix camera
        { nearClipDepth = Length.meters 0.1
        , farClipDepth = Length.meters 100
        , aspectRatio = 16 / 9
        }

Projection to screen space

You can also use a Camera3d to project points, lines, triangles and polylines from 3D to 2D:

import Point3d.Projection as Point3d
import LineSegment3d.Projection as LineSegment3d

screen =
    Rectangle2d.from Point2d.origin
        (Point2d.pixels 800 600)

point2d =
    point3d |> Point3d.toScreenSpace camera screen

lineSegment2d =
    lineSegment3d
        |> LineSegment3d.toScreenSpace camera screen

This allows you to, for example, do a perspective projection of 3D points and lines into 2D so that those points and lines can be rendered with SVG (taking advantage of SVG features like perfect circles and dashed lines which are difficult to do with WebGL):

Roadmap

Several more features are planned:

• More Viewpoint3d constructors other than just lookAt and orbit
• More 3D-to-2D projections (directions, axes)
• Construction of 3D cut planes from 2D on-screen lines

Questions? Comments?

Please open a new issue if you run into a bug, if any documentation is missing/incorrect/confusing, or if there's a new feature that you would find useful. For general questions about using elm-3d-camera, try:

• Joining the #geometry or #webgl channels on the Elm Slack, or sending me (@ianmackenzie) a message - even if you don't have any particular questions right now, it would be great to know what you're hoping to do with the package!
• Posting to the Elm Discourse forums

You can also find me on Twitter (@ianemackenzie), where I occasionally post elm-geometry-related stuff like demos or new releases. Have fun, and don't be afraid to ask for help!