When such a rare event does happen, the result is an unnatural bright speck. This does not work well when the light is large and the roughnessВ is low, because the chances are very small that a random sample on a large light source will fall within the very narrowВ specular lobe of a smooth, mirror-like BRDF. The first image uses traditional area light source sampling. (Note how in the Veach example, sampling the BSDF works for area lights and not tiny spots, and sampling favouring the lights does the opposite)Д«elow is The FoundryвЂ™s replication of this classic shot in three images each showingВ five rectangles using a highlyВ specular GTR material with roughness settings of 2%, 4%, 8%, 16%, and 32%. In the original 1997 black and white original there are four area lights, varying in size by a factor of three from their neighbors (and varyingВ in radiance by a factor of nine so that they each emit the same total energy).

In VeachвЂ™s 1997 thesis and in a paper he co-published just prior (1995 Veach &В Guibas), this is an image which shows the problem and solution solved via MIS.

As the renderer was not slow, comparatively speaking, this new solution will be welcomed by users for both its speed and improved noise performance. The user can specify whether to use MIS for diffuse shading, specular shading, both, or neither. Users canВ activate the MIS using the Direct Light MIS channel of theВ render item. вЂњOr, if the user enabled the lightвЂ™s Visible to Reflection Rays option, its specular shading was handled as partВ of computing blurry reflections, which involves choosing random directions according to the BRDF and seeing if rays firedВ in those directions hit the light source.вЂќДЇrom what we saw, both of theseВ approachesВ are likely to beВ noisy compared to the same scene rendered with the new MIS approach for the same render effort. In earlierВ releases, the shading was computed by choosing вЂњrandom sampleВ points on the light source, determining if they are visible by firing shadow rays, then multiplying the incoming light by theВ surfaceвЂ™s BRDF,вЂќ commentedВ Shane Griffith, MODOвЂ™s Product Marketing Manager. For both spec and diffuse, MIS can greatly reduce visible noise in MODO renders. In short, MIS produces much better results, more accurate and just as about as good as you can do.В MIS in 901 has been implemented for diffuse and specular shading and is in complete sync with the move toВ area light sources. This leads to estimators that have low variance for a broad class of integrands.вЂќ It uses more than one sampling technique to evaluate an integral, and then combines these samples in a way that is probably close to optimal.

вЂњвЂ¦include a new technique called multiple importance sampling, which can greatly increase the robustness of Monte Carlo integration. In 1997 Veach, a Sci-Tech Oscar winner for his rendering contributions, published a range of key rendering theories which: Top of this list is Multiple Importance Sampling (MIS), an addition in the spirit of Eric VeachвЂ™s 1997 thesis (the bible that all the top renderers have consulted when implementing MIS). In MODO 801, the renderer was very much in an acceptable category of speed and performance, but with 901 there have been some serious additions. It is also important given the cross-product module level technology swaps we are seeing, with key tech from all The Foundry products being swapped in each otherвЂ™s product road maps. This core technology is not just for 901, but it is key to several projects still very much under wraps. After all, the primary strength ofВ MODO is modeling, no one would be upset if their renderer was adequate for students and indie users but not really fast or highly optionedвЂ¦well, everyone except theВ MODO guys, who are it seems committed to having serious render technology in-house. TheВ MODO team could have walked away from making their renderer a serious production option, leaving the market open to third party renderersВ such as V-Ray, RenderMan, Maxwell or Arnold.

The renderer in 901 is very much a viable production renderer. While those features were interesting (see UDIM below), Mike Seymour has this exclusive look at some of the changes in the MODO renderer which the team did not discuss but are just as exciting. The Foundry showed some new features of the new MODO 901 release today in a webinar.

Modo 801 shadow material