Lightshow

Lightshow is a raytracer written purely in Go.

Quickstart

To render a scene using the default settings, go ahead and execute:

make

You will need to have Go installed for this to work.

Details

The rendering process is triggered by calling the Render method, which is available on the Renderer type. You can find the Renderer struct in the pkg/renderer package.

The call would look something like this:

var renderOptions = ... // TODO
var world = ... // TODO

// Start rendering.
if err := renderer.New(renderOptions).Render(world); err != nil {
    panic(fmt.Errorf("failed to render: %w", err))
}

Now, let's focus on the renderOptions and world values.

RenderOptions

Quickstart value:

const (
	// aspectRatio of the rendered image.
	aspectRatio = 16.0 / 9.0
	imageHeight = 720
)

var cameraOptions = &camera.Options{
	LookFrom:            utils.NewVec3(13, 2, 3),
	LookAt:              utils.NewVec3(0, 0, 0),
	Up:                  utils.NewVec3(0, 1, 0),
	AspectRatio:         aspectRatio,
	FieldOfViewVertical: 20,
	Aperture:            0.1,
	FocusDistance:       10,
}

var renderOptions = &renderer.Options{
	Camera:            camera.New(cameraOptions),
	ImageWidth:        imageHeight * aspectRatio,
	ImageHeight:       imageHeight,
	SkyColour:         utils.NewColour(0.5, 0.75, 1.0),
	MaxDiffusionDepth: 50,
	SamplesPerPixel:   50,
	MaxWorkers:        400,
	OutputFile:        "./dist/image.jpg",
}

As you can see, RenderOptions requires CameraOptions so we defined it first.

All the fields in these options are documented in the code. Find CameraOptions definition in the pkg/camera package and that of RenderOptions in the pkg/renderer package.

World

World is a simple slice of shapes that will be rendered.

Quickstart value:

var world = shapes.NewGroup(
	// Ground.
	&shapes.Sphere{
		Center: utils.NewVec3(0, -100000, 0),
		Radius: 100000,
		Mat:    mats.NewMatte(utils.NewColour(0.5, 0.5, 1)),
	},
	// Middle glass sphere.
	&shapes.Sphere{
		Center: utils.NewVec3(0, 1, 0),
		Radius: 1.0,
		Mat:    mats.NewGlass(1.5),
	},
	// Front metallic sphere.
	&shapes.Sphere{
		Center: utils.NewVec3(4, 1, 0),
		Radius: 1.0,
		Mat:    mats.NewMetallic(utils.NewColour(0.7, 0.6, 0.5), 0),
	},
	// Back matte sphere.
	&shapes.Sphere{
		Center: utils.NewVec3(-4, 1, 0),
		Radius: 1.0,
		Mat:    mats.NewMatte(utils.NewColour(0.4, 0.2, 0.1)),
	},
)

With these values defined, the Render method can now be called. It will take some time to render based on the number of shapes and other graphical properties.

References

• Ray Tracing in One Weekend