Image based on Inyo County's Logo
The Inyo Renderer Logo
A Monte Carlo Path Tracer by David Cuny

 Inyo is (more or less) Dead 

Inyo was originally written because I couldn't find a nice Java raytracer. Since then, Sunflow pretty much supplies all the functionality (and more) that I was hoping to get from Inyo. Additionally, approximate ambient occlusion (pdf 3.4 Meg) has replaced my need to do path tracing.

You might want to check out these this list for other open source renderers.

Image rendered with Inyo

Rendered with the Inyo path tracer. The only light in this scene comes from the sky. Yes, I know the sampling is buggy.
The cartoon rabbit is a free model from
Eggington Productions.

What Is Inyo?

Inyo is an open source Monte Carlo path tracer renderer written in Java. The main purpose for Inyo is to supply JPatch with a renderer that provides indirect skylight lighting along the lines of Marcos Fajardo's Arnold Renderer. Inyo can be used as a stand alone renderer, apart from JPatch.

Summary of Inyo Features

Using Inyo

You can get the source code for Inyo here. You will need to compile it with Java, which should be simple enough:

Once Inyo has been compiled, you can then execute it with the instruction:

where filename is the name of the file to render. Inyo can currently only render files stored in the "generic" format of the JPatch animation program.

Please refer to the include readme file for documentation on the command line options currently available (not all options in Inyo can currently be set in the command line).

What's Happening with Inyo

I've done quite a bit of development on Inyo, including:

I'll upload the latest version of Inyo when I get a chance, in case anyone is curious to look at the code. However, I won't claim that it's good code, and there's no real file format for loading models into Inyo. In the mean time, you can always send me an email if you want a copy.

Inyo's development has been tied to bleeding-edge versions of JPatch, and hasn't been stable enough to post. Problematically, import of .obj files is now broken, and the Inyo now relies on being supplied with correct normals and interpolated vertices. Until this is fixed, Inyo can't really be used for a stand-alone renderer for anything that doesn't export normals.

When JPatch hits a stable release, I'll try to get Inyo into a form that can be used "stand alone". It's also included with the JPatch source code.

What's this Monte Carlo Stuff?

When rendering a scene, computers have traditionally used direct illumination – the illumination of a point is based on the ray from the eye to some point p, and another ray from the point p to a light. The illumination calculation takes into account illumination that comes directly from the light, but not illumination which might take a different path, such as from the light to the ground, and then to point p, and then to the eye.
Image of line of sight ray from eye to point p, and light ray from point p to light.
The following image was produced using traditional ray tracing. The jitter for the following scene is set to 3, which means each pixel is an average of 9 samples. Note that soft shadows are enabled, so the shadow becomes blurred the further it is from the rabbit:

Plain raytracing image rendered with Inyo

Since the indirect illumination of a scene can come from (essentially) random directions, the path tracer mimics this by sending lots and lots of rays at a given point p in random directions. This is random sampling is referred to as a "Monte Carlo" technique. If enough rays are sent out, the path tracer will eventually converge on a solution that includes many different light paths. The following image is a "pure" Monte Carlo image, with 100 samples per pixel. Note that the rendering time is much higher, and the result has a lot of "noise" in it:

Image generated by "pure" path tracing

Rather than create new samples at every new point p, a technique known as irradiance caching saves sampled points into a cache. When the path tracer needs to determine the illumination (irradiance) at a new point, if first checks to see if there are samples in the cache similar enough to the point in question be used to create an estimate of the illumination instead.

Besides reducing the number of samples that need to be taken, irradiance caching has the happy side effect of virtually eliminating the high level of noise created by the path tracer.

The image below shows the same scene as the prior one, but uses the irradiance cache to estimate most of the samples. The white dots indicate the points where Inyo actually sampled the scene for irradiance. Samples are taken more frequently based on how far apart the samples are, the difference in curvature, and the average distance of shadow casting objects from the sample point:

Image generated with Inyo showing only sky contribution

Inyo is able to provide a complete illumination estimate by using the ray tracer to calculate direct illumination, and the path tracer and irradiance cache to estimate indirect illumination. The image below shows the result:

Image generated with Inyo's path tracer enabled

Unfortunately, the irradiance cache is broken in the current release.
Last Updated: Wednesday, March 2, 2005