Information about the literal work Min shading rate in the official HELP lodged in very general terms, and all that is clear is that this feature allows you to allocate less ray to render effects such as glossy reflections, GI, area shadows, for the sake of quality Sampling Anti-aliasing . The higher the value Min shading rate, the higher the kachetvo AA, and lower the quality of the rest of the effects of shading. And also, that the Min shading rate is particularly noticeable (effective) to work with the AA sampler Progressive sampler.
As for the Progressive sampler, it Unbiased algorithm similar to that used in the GPU rendering . It does not calculates the color of the pixel of the final rendering in accordance dedicated to rendering samples and adds the number of samples with each new blunder, at the same time changing the color of pixels to new, Bole accurate and so on to infinity or before "ugretsya" in the specified thresholds (Render time > 0, Max. subdivs).
The Min. and Max. Subdivs functionality corresponds to the name.
Min. subdivs - controls minimum number of samples to be taken from the scene for the formation of the color of one pixel. Literal number of samples is the square of the value of Min. subdivs.
Max. Subdivs - controls maximum number of samples to be taken from the scene for the formation of the color of one pixel. When you reach this amount - rendering pixel color stops.
V-Ray 3, nothing at all is not fundamentally different from the previous one. It adds several new features as well as slightly worked interface. That's why you can boldly explore completely the entire series of articles on "the best settings-Ray the V» . The stated there is information on the example of V-Ray 2 is relevant now, including, and ways to speed up the rendering. One of the lessons of this series, the lesson « the V-Ray - the DMC a Sampler », just on accelerated rendering .
The only innovation that I am pleased to note, this new algorithm reykastinga -based command library Embree for Intel processors. Activate it tick « the Use Embree » rollout System, Settings tab. In some scenes, the use of this reykastera accelerates rendering by half. In my practice, such scenes bolshenstvo. I would skzal, this is the first renderer revolutionary improvement over the past couple of years. Of course, this feature will work only with an Intel processor. If it is activated, for example, on a computer with AMD CPU, the renderer will generate an error does not continue to work.
Hello!The answer lies in the essence of these settings.Min shading rate - allows from all the rays of the scene's tracing, to force more of the rays to refine the shading effects (roughly speaking about the quality of the materials), taking a certain number of rays from the antialiasing algorithm. That is, in this case it is shading that will be better, and antialiasing will be calculated less accurately.Nominally, with Min shading rate - 1, the number of beams allocated to all effects is the same (more precisely, originally allocated by the developers of the renderer). If you want, by reducing the quality of anti-aliasing, for example, raising the quality of materials calculation, then you need to increase this value.Theoretically, this parameter should not significantly affect the speed, since the total number of rays tracing the scene will be unchanged, but the quality of antialiasing will deteriorate.For my scenes, this setting is "sewed on soap", I prefer the quality of materials to determine locally in their settings, but perhaps someone in a particular situation this setting will be useful.As for Divide shading subdivs, in order to understand how this function works, it is necessary to clearly understand what Antialiasing is technically, namely that AA is an oversampling of the pixel being calculated. For simplicity, let's consider the shading calculation (illumination of geometry). With AA = 1, the renderer calculates the pixel directly, that is, "removing" the information from the geometry of the scene and immediately forming the final color of the pixel. To do this, he "looks" at the calculated point in the scene and "sees" that, for example, 64 rays from the light source hit it. After that, the final color of the pixel is calculated by 64 rays of illumination. At AA = 2, the pixel is conventionally divided in two horizontally and in two vertically, i.e. Subpixel. And the renderer again for EACH of the subpixels looks at the 4 corresponding points of the scene and for EACH of them it calculates its color, according to the same principle as for the pixel. Then the color values of 4x subpixels are averaged and a more accurate color of the final pixel is obtained. That is, the color of the pixel is taken not directly from the scene, but through sub-pixels. And here is the question, how many rays are calculated for 4 subpixels? And that's where it all depends whether Divide shading subdivs is ticked or not. If not included, then each subpixel is calculated according to the standard scheme, that is, for the calculation of EACH subpixel, 64 beams from the IC will be allocated. As a result, to calculate a single pixel with AA = 2 in the total it is necessary to calculate already 64 * 4 = 256 beams of IP. If the Divide shading subdivs function is activated, then for each subpixel the number of beams that would be allocated to the pixel in the straightforward rendering, we have this 64, will be divided by the number of subpixels, in our case this is 4e. That is, for each subpixel, not 64 beams will be allocated, but only 64/4 = 16 rays. For the rendering of 4 subpixels, and after a single pixel, even with AA = 2, no more than 64 pixels will be allocated😁 In other words, the total number of beams (subdivs) for rendering the final pixel will not beckon with the AA change. Increasing or decreasing AA will not increase or decrease the number of subdivs for rendering, for example, illumination. The same applies to subdivs for other effects.However, the function of disabling this dependency was required by V-Ray users and the developer company went to the meeting.As for the usefulness of switching off the division of the sampling samples into antialiasing samples, I will not give my opinion, just give a comment from the official help from the developers:"In our humble opinion, this approach (switching off subdivs division for subpixels) does not speed up the miscalculation and does not make the adjustment of the quality of the desired effects easier, rather introduces additional confusion, but some users, especially those who switched to V-Ray from other renderers, want to have The ability to disable the dependence of the quality of shading on the quality of antialiasing, so it's the same [... so be it) "😁