Ray Tracer in Kotlin

A long time ago in 2010 I read the excellent book "Ray tracing from the ground up" by Kevin Suffern. While reading this book

• I translated the C++ code to Javan
• made the code more object oriented
• made the code thread-safe for parallel execution
• wrote a DSL for easy scene creation and manipulation in Groovy
• Refactored the code quite a bit to develop nice object-functional program

Rewrite to Kotlin

From 2018-2020 I ported the code to Kotlin. The groovy DSL is not a Kotlin DSL. In 2022/2023 I experimented with Kotlin multiplatform and it worked, but the APIs were changed too often. So I reverted back to JVM only in 2024.

The old code with Java and Groovy is available in the branch groovy-java.

Running

Run the different versions with

$ ./gradlew build
$ ./gradlew swing
$ ./gradlew run --args="--world=World20AreaDisk.kt --tracer=AREA --renderer=FORK_JOIN --resolution=1080p"
$ ./gradlew run --args="--world=World66.kt --renderer=FORK_JOIN --resolution=720p"
$ ./gradlew run --args="--world=World66.kt --renderer=PARALLEL --resolution=1080p"
$ ./gradlew run --args="--world=World42.kt --renderer=COROUTINE --resolution=2160p"

Choose a scene file with a left click, see the source code and click render to render it.

Some examples require PLY files that are available on the net.

Describing scenes with a DSL

For easier manipulation of scenes I implemented a DSL for scenes.

The following image

is described by the following Kotlin program:

package net.dinkla.raytracer.examples

import net.dinkla.raytracer.colors.Color
import net.dinkla.raytracer.world.Builder
import net.dinkla.raytracer.world.WorldDef

object World48 : WorldDef {

    override fun world() = Builder.build {

        camera(d = 1250.0, eye = p(0.0, 0.1, 10.0), lookAt = p(0, -1, 0))

        ambientLight(color = Color.WHITE, ls = 0.5)

        lights {
            pointLight(location = p(0, 5, 0), color = c(1.0), ls = 1.0)
        }

        materials {
            phong(id = "sky", cd = c(0.1, 0.7, 1.0), ka = 0.75, kd = 1.0)
            reflective(id = "white", ks = 0.7, cd = c(1.0, 1.0, 1.0), ka = 0.5, kd = 0.75, exp = 2.0)
            phong(id = "red", ks = 0.9, cd = c(0.9, 0.4, 0.1), ka = 0.5, kd = 0.75, exp = 10.0)
            phong(id = "orange", ks = 0.9, cd = c(0.9, 0.7, 0.1), ka = 0.5, kd = 0.75, exp = 10.0)
        }

        objects {
            smoothTriangle(a = p(-5, 0, -1), b = p(-5, -1, 1), c = p(-3, 0, 1), material = "orange")
            plane(point = p(0.0,-1.1,0.0), normal = n(0, 1, 0), material = "white")
            ply(material = "red", fileName = "resources/TwoTriangles.ply")
            sphere(center = p(2.5, 0.5, 0.5), radius = 0.5, material = "orange")
            sphere(center = p(1.5, 1.5, 1.5), radius = 0.5, material = "sky")
            triangle(a = p(-3, 0, -1), b = p(-3, -1, 1), c = p(-1, 0, 1), material = "orange")
            triangle(a = p(3, 0, -1), b = p(3, -1, 1), c = p(5, 0, 1), material = "orange")
        }
    }
}

See my home page for more information and examples.

Here is another example:

Requirements

The Swing user interface runs with all Java versions.

Keywords

ray tracing, rendering, Java, Groovy, DSL, ambient occlusion, Kotlin

Author

Written by Jörn Dinkla.

Remarks

The folder resources contains the following:

• TwoTriangles.ply is from Kevin Suffern, the author of the book.
• Isis.ply was downloaded from Cyberware (dissolved since 2011 )

Upgrade dependencies

The project uses refreshVersions

$ gradle refreshVersions

(c) 2010 - 2024 Jörn Dinkla https://www.dinkla.net