Lykta - A Work-In-Progress Physically-Based Renderer

Introduction

Lykta is a CPU renderer that is not meant for any practical usage. It's purely a hobby renderer for myself to use when I want to implement or try new ideas. However, the goal is to keep the renderer fairly simple, e.g. support only triangle meshes, a single material model and only mesh emitters.

Future plans include possibly creating a Houdini plug-in...

Building

This project uses CMake version 3.12 or higher for building. Everything should work automatically on Windows and Linux with the correct version of CMake, but on OS X some additional work is necessary.

The project requires Embree to be installed on the computer and discoverable by CMake. Follow the installation instructions at: https://embree.github.io/downloads.html

Clone the repository using Git

git clone --recursive https://github.com/jonathangranskog/lykta.git

To build the project, use the following commands or use cmake-gui on Windows.

cd lykta
mkdir build
cd build
cmake ..
make

OS X

Unfortunately, OpenMP is not fully supported by OS X at this moment. However, you can easily gain access to it by using Brew.

brew install libomp

The CMake build process assumes the default Brew installation on OS X so if you change your install paths then you might have to modify the CMakeLists.txt file.

Example scene file:

{
  "camera" : {
    "type": "PerspectiveCamera",
    "resolution" :  [800, 800],
    "center": [ 0.0, 0.5, 1.05 ],
    "lookat": [0.0, 0.5, 0.0],
    "fov": 45.0,
    "nearclip": 0.01,
    "farclip" : 100.0
  },
  "objects": [
    {

      "file": "E:/Projects/lykta/spheres.obj",
      "material": "white"
    },
    {

      "file": "E:/Projects/lykta/emitter.obj",
      "material": "emitter"
    }
  ],
  "materials": [
    {
      "name": "white",
      "diffuseColor": [1.0, 1.0, 1.0],
      "emission" : [0.0, 0.0, 0.0]
    },
    {
      "name": "emitter",
      "diffuseColor": [ 0.0, 0.0, 0.0 ],
      "emissiveColor" :  [10.0, 10.0, 10.0]
    }
  ]
}

Houdini Export

In the Houdini folder you can find two digital assets that are used to export Houdini scenes directly into Lykta. This has only been tested with H17.0.416. The exporter is a python script in the Lyktasave digital asset. It runs through every node in the obj/ and looks for NULL nodes named "LYKTA_EXPORT" and these are then saved as .obj files that are read by Lykta. REMEMBER, to add normal attributes to geometry!

In addition, all "principledshader" materials are exported as Lykta materials that are then connected to their respective geometry. The camera exported into the Lykta scene HAS to be a "lyktacam", which is the other digital asset provided. It works exactly like a normal Houdini camera. Emitters are only created from geometry with materials that have emission set to a value larger than 0. No native Houdini lights are supported currently except environment lights (HDR files only).

The Lyktasave node has a few buttons and parameters which need to be setup before usage. All of these are pretty self explanatory.

• 'Export' exports the geometry and JSON scene file
• 'Render Frame' renders the current frame
• 'Render Frame Range' renders an animation based on the "Frame Range" parameter
• 'Executable' is the path to a built Lykta executable
• 'Save Folder' is the location where scenes, images and geometry will be saved
• 'Samples' is just the number of samples used for each frame
• 'Frame Range' refers to the range of frames rendered if "Render Frame Range" is pressed