The scene clpt.clpt (1280x640, 51,000+ SPP), rendered in just over an hour.

• Monte Carlo Path Tracing
• Real-time rendering speed
• SAH BVH (Surface Area Heuristic Bounding Volume Hierarchy) acceleration structure for meshes
• Progressive rendering
• Depth of Field (with pentagonal bokeh) based on the thin-lens model
• Image-Based Lighting using an HDR environment map
• Volumetric Path Tracing with homogeneous media using full scattering
• Custom, readable scene (.clpt) and configuration (.clptcfg) file formats

• Spheres
• Triangle Meshes
• Ground Plane

• Lambertian diffuse
• GGX Plastic
• GGX Dielectric/Glass
• Mirror
• Metals

*all materials (excluding metals) can be emissive

*all materials can use a homogenous Isotropic Scattering Medium (only transparent materials will be affected, however)

Run the file run.command to start the engine. This will build, compile, and execute the program. You can then choose from the OpenCL-capable devices available on your machine (this project is currently a WIP, so not all hardware will work).

After a bit of initialization, the demo scene will load and the display will appear.

• W/S to go forward/backward
• D/A to go right/left
• R/F to go up/down
• click and move mouse to look around

• G/H to increase/decrease the aperture radius
• T/Y to increase/decrease the focal distance

• SPACE to reset position and camera attributes
• ESC to Quit

CLPT's configuration files, specified with a .clptcfg or .clptcfg.txt extension, are CLPT's way of allowing the user to specify basic parameters of the simulation, such as resolution, the name of the scene file to be used, and whether the scene is interactive (the following example is interactive, as long as the first word of a line is not interactive interactivity will be disabled).

width: 1920
height: 1080
scene: default
interactive

CLPT's scene files, specified with a .clpt or .clpt.txt extension, are CLPT's way of allowing the user to specify all aspects of a scene.

Here's the scene file for default.clpt:

 # set camera attributes
setCameraPosition 4.216578948221484 2.375 0.34339889486771863
setCameraForward -0.7156478248575902 -0.05930652721420354 0.6959388813727766
setCameraUp -0.042517570286490336 0.9982398187959389 0.04134634672114762
setCameraFocalDistance 7.370589916300956
setCameraApertureRadius 5e-2

 # toggle options
enableIbL
enableDOF
enableGround

 # specify IbL path and set IbL weights by component (or background color if no IbL)
iblPath res/Frozen_Waterfall_Ref.hdr
backgroundColor 1.0 1.0 1.0

 # set a vector type variable 'blue' to (0.3, 0.3, 0.9)
set vec3 blue 0.3 0.3 0.9

 # create a material 'bluePlastic', a plastic material with a diffuse color of 'blue' and a roughness of 0.103'
material bluePlastic plastic blue 0.103

 # add a deer mesh to the scene at position (-3, 0, 5) with scale (0.25, 0.25, 0.25) using the 'bluePlastic' material
mesh deer -3 0 5 0.25 0.25 0.25 bluePlastic

For a longer, more complex example, go to the scene file used to produce the image just below the title of this page at res/clpt.clpt.

Thank you for checking out CLPT!

Further optimizations could be implemented to improve the speed and efficiency of CLPT

• SBVH (Stich et al. 2009) has been shown to have an identical worst-case performance to the SAH BVH, while boasting a significant increase in best-case performance

• Minimize branching to reduce execution divergence
• Optimize memory alignment
• Use local memory more often
  • Currently using global memory to store geometry data and constant memory to store material data
  • Local memory has been shown to be accessible up to 100x faster than global memory, though is certainly limited in size
• Reduce Idle Threads
  • It is likely that with local group sizes larger than several pixels, many threads will escape the scene early or terminate early due to Russian Roulette
    • As a result, these threads are idling, which will worsen the consequences of execution divergence

• Better streamlines the path tracing pipeline for GPU usage

There are many features which could be implemented to increase the user experience, photorealism, and capabilities of CLPT

• Certainly feasible for the renderer