Join Brian Bradley for an in-depth discussion in this video How to use the adaptive engine, part of V-Ray 3.0 for 3ds Max Essential Training.
- In contrast to the Fixed-Rate engine, the Adaptive system, as the name suggests, does indeed add adaptivity to the image sampling process. Meaning that, based on a number of user-specified input parameters, the engine can and will make some very deliberate choices about where and how it decides to use the number of samples that have been made available to it. In the Render Setup dialogue then let's come in to the V-Ray tab, and in the image sampler rollout, switch from Fixed to the Adaptive engine.
Noting straight away of course that our Fixed image sampler rollout now becomes the Adaptive image sampler rollout. This of course being where we can access all the control parameters for the Adaptive engine. The options used here to determine the number of samples available for use in this system are these Min and Max values. Now right out of the gate here, we do need to sound a quick note of warning in that we never really want to be setting the same numeric value in the Min and Max fields. Doing so would kill adaptivity in the system, and at that point we would simply be rendering as if using the Fixed-Rate engine.
Let's load up the first of the images sitting in our history list here and take a look at how this particular system would render our scene using just the default Min and Max Subdiv values of 1 and 4. Straight away we see that what we get is already much cleaner looking than our initial Fixed-Rate render from the previous exercise. If I zoom to 100% here, the fine detail in our texture maps looks better. The shadow noise on our solid colors, while still visible, is in no way overbearing.
And of course the geometry edges at 100% zoom are already looking nice and clean. Let's go ahead and try to really clean things up by pushing the quality settings to Min and Max Subdivs of 1 and 8, 8 of course being the same Subdiv value that we jumped to in our Fixed-Rate exercise. What we see as we load our second render into the frame buffer then might be a bit of a surprise. Because although the render times have gone up from just over four minutes to now just short of eight, we aren't really seeing the same jump in quality that our Fixed-Rate exercise produced.
In fact if I just load our first render back into channel A, and then middle mouse pan across the image to the far right, you can see as we examine the shadow being cast on to the wall by the cabinet that our faster, lower sample version of the render actually produced a smoother, more noise-free result. Indeed, even if I loaded our third image in here, which is using Min and Max values of 1 and 16 respectively, our original render still holds its own. This seemingly odd behavior is down to the way in which V-Ray, behind the scenes, handles the usage of both primary and secondary sampling rays in a scene.
Indeed, one thing we do need to realize is that the Adaptive image sampler doesn't automatically make use of all samples available as determined by the Max Subdivs parameter. It may well be that certain areas of our image don't meet the criteria for all of those samples to be used. That criteria by default being determined by the Noise threshold value that can be found in the Global DMC rollout. Let's see what happens if we drop that value from its default of 0.01 to a generally accepted production level setting of 0.005.
Loading our fourth image into the V-Ray frame buffer and comparing it to our previous Min 1 Max 16 render, shows that we have now, particularly in noisy areas, made a noticeable improvement, although render times have pretty much doubled. This is because with our current setup, we are letting primary samples do all of the work. One way to improve the situation would be to tell V-Ray to let secondary samples in the scene take more of the load. Now we could do this by going through all of the materials and lights in our scene and increasing the Subdiv values that we find there.
Another way to accomplish the same result but using just a single global parameter would be to make use of this Min shading rate option, which is available no matter which of the four image sampling engines we're using. Higher shading rate values tell V-Ray to spend less time using the primary rays and instead focus more effort on the sampling of secondary ray shading or noisy effects in the scene such as glossy reflections, GI area shadows and so on. Setting this option to a value of 3 would produce our fifth and final render.
Which, although as you can see in a comparison makes no discernible difference to the final quality of the render, does however shave about three minutes off the render time. Which, typically speaking, is always going to be a welcome scenario, as it now leaves us free to increase our Max samples value in order to further clean up our render. Now in terms of weaknesses, there really aren't any as such that I would ascribe to the Adaptive image sampling engine. Other than the fact that, whilst being able to work adaptively, it isn't able to perform any kind of undersampling in the scene, even on areas of the image that would most definitely benefit from it.
This is why in our next exercise, we are going to look at an engine that can perform undersampling, this being the Adaptive Subdivision option.
- Using the new UI elements, Quick Settings, and revamped Frame Buffer
- Understanding color mapping modes
- Adding V-Ray light types
- Working with the V-Ray Sun and Sky systems and dome light
- Using irradiance mapping and light cache
- Working with diffuse color maps
- Making reflective materials
- Creating a translucency effect
- Using the new SSS and skin shaders
- Ensuring quality with image sampling
- Working with the adaptive subdivision engine
- Controlling the physical camera
- Working with FX tools such as VRayFur and VRayMetaball
- Stereoscopic 3D rendering
- Using Render Mask
Skill Level Intermediate
Q: This course was updated on 02/02/2016. What changed?
A: We added tutorials on the new 3ds Max camera tool, which replaces the defunct V-Ray Physical Camera. The author also includes a method for creating a V-Ray camera via scripting.
Q: This course was updated on 04/19/2018. What changed?
A: New videos were added that cover V-Ray 3.1 to 3.3 updates.