Howard

Howard is a parallelized ray-tracer written in Haskell based on the "Ray-Tracing in a Weekend" tutorial. Howard is capable of rendering scenes involving metal, lambertian, or dielectric spheres.

Getting Started

Howard requires Stack to run. To get started run the following command

stack setup
stack build
stack exec howard-exe <single?> <scene?> > <imagename>.ppm

To run the single-threaded implementation of Howard, include the single argument when running stack exec, otherwise do not include the argument for the parallelized version. To generate one of the given the test scenes, include the name of the scene as an argument. Not including a scene argument will generate the default scene. to output the results to a file, pipe stdout to a ppm file.

Generating a Test Scene

Howard has 6 test scenes to render

Default Scene

To generate this scene do not use a scene argument when running stack exec

Lambertian Sphere Scene

To generate this scene use lambertian as the scene argument when running stack exec

Metal Sphere Scene

To generate this scene use metal as the scene argument when running stack exec

Dielectric Sphere Scene

To generate this scene use dielectric as the scene argument when running stack exec

Hollow Glass Sphere Scene

To generate this scene use hollow-sphere as the scene argument when running stack exec

Final Scene

To generate this scene use final as the scene argument when running stack exec

Generating a Custom Scene

To generate a custom scene, reconfigure Main.hs to define a set of spheres in the world.

Defining Materials

To define a dielectric surface, construct an instance of the Dielectric data type with an index of refraction. To define a lambertian surface, construct an instance of the Lambertian data type with a 3-Dimensional color vector. To define a metal surface, construct an instance of the Metal data type with a 3-Dimensional color vector and a "fuzziness" constant.

        material1 = Dielectric 1.5
        material2 = Lambertian (Vec3 0.4 0.2 0.1)
        material3 = Metal (Vec3 0.7 0.6 0.5) 1.0
        material_ground = Lambertian (Vec3 0.5 0.5 0.5)

Creating Spheres

To create a sphere, construct an instance of the Sphere data type with a position vector, radius, and material.

        sphere3 = Sphere (Vec3 0 1 0) 1.0 material1
        sphere2 = Sphere (Vec3 (-4) 1 0) 1.0 material2
        sphere1 = Sphere (Vec3 4 1 0) 1.0 material3
        groundSphere = Sphere (Vec3 0 (-1000) 0) 1000 material_ground

Creating a World

To create a world, simply add the defined spheres to a HittableList

        world = HittableList [sphere1, sphere2, sphere3, groundSphere]

Initializing the Camera

To initialize the camera, initialize its aspect ratio, width, sampling size, field of view (FOV), position, direction to look, and up direction.

        aspectRatio = (16.0/9.0)
        width = 1920
        samples = 100
        vFov = 20
        lookFrom = Vec3 13 2 3
        lookAt = Vec3 0 0 0
        vUp = Vec3 0 1 0

        cam = initialize aspectRatio width samples vFov lookFrom lookAt vUp

Rendering the scene

To render the scene, simply call renderParallel or render given the defined camera and world

        -- Parallel rendering
        renderParallel cam world

        --Single threaded rendering
        render cam world