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How to use the Adaptive DMC sampler

From: V-Ray 2.0 for Maya Essential Training

Video: How to use the Adaptive DMC sampler

In contrast to the Fixed Rate Image Sampling Engine, the Adaptive DMC System, as the name suggests, does indeed add adaptivity into the Image Sampling process. This means that based on user input parameters, the engine can make some very deliberate choices about where and how it chooses to place and use samples in the scene. Again, let's set the system up. If we come up to our Render Settings window, come into the V-Ray tab, we see we have the Image sampler roll out open by default. Let's go to our Sampler type dropdown and set now the Adaptive DMC system to be active.

How to use the Adaptive DMC sampler

In contrast to the Fixed Rate Image Sampling Engine, the Adaptive DMC System, as the name suggests, does indeed add adaptivity into the Image Sampling process. This means that based on user input parameters, the engine can make some very deliberate choices about where and how it chooses to place and use samples in the scene. Again, let's set the system up. If we come up to our Render Settings window, come into the V-Ray tab, we see we have the Image sampler roll out open by default. Let's go to our Sampler type dropdown and set now the Adaptive DMC system to be active.

Now, in here we have a number of user control parameters. We have our Min and Max Subdivisions. We also have this Lock threshold to DMC sampler Threshold setting, this means that at this moment in time the system is going to be working along with this Adaptive Threshold value to determine how to clean up noise effects in the scene and how to use Image Samples. One thing that is worth making note of here is the fact that we never really want to set the same value in our Min and Max subdivs. Essentially when we do that we kill adaptivity in the system and any render we take would be identical to using the Fixed Rate Image Sampling Engine with a subdivision value of 1 set.

So let's work with some parameters here and see what kind of effect it has on rendering our scene. So let's set Min subdivisions at 1, we'll set the Max subdivisions value to 3, and I'm just going to come across to our Adaptive Threshold value here and I'm going to set it to be 0.1. That means it's not really sensitive to noise in the scene at all. Now, if we jump across to Adobe Bridge and just navigate to our pre-rendered files, so just come into Exercise_Files, assets, Ch06, and of course we're working with the DMC system now, so let's choose our first image, Spacebar to maximize, then Left Mouse click to zoom in.

And as you'd perhaps expect, we have quite a low quality image, although apart from the noise, lots of areas of the scene aren't fairing too badly. Our lined material is looking pretty good. Our noise material, not looking too bad, there are some gaps in it that we can see, but hopefully they will clean up as we increase our quality settings. And of course we're getting a very fast render time of just 50 seconds from this scene. Obviously, we need to push our quality settings though. So let's go back into the Maya Application. So come to our Image Sampling controls and let's now set a Minimum subdivision value of 3 and we'll set Maximum to 7.

We won't touch the DMC Sampler controls, we'll just see what kind of an effect that makes as we look at our second render inside of Bridge. We can see we have cleaned up the noise somewhat. Our scene is definitely improving. Still lots of problem in there, lots and lots of noise that we can see. We have increased our render time now to 3 minutes and 7 seconds. Clearly then we need to push the quality. But if we jump back into Maya, oftentimes these Min and Max subdivs are not necessarily the best way to approach adding extra quality to the scene.

See, at this moment in time our DMC Sampler controls are not really sensitive to any noise that can be found. They're not really allowing the DMC System to use the full amount of samples available to it. So let's set this to a very sensitive value of 0.005. I'm going to keep our Min and Max at 3 and 7, and if we go back into Bridge and select our third render, you can see we really do clean up a lot of that noise. So things are starting to look very nice indeed.

We can see noise problems in the shadow areas. We can see fine grain noise on our diffused block, and of course we have bumped up our render time now to just over 14.5 minutes. Clearly, we need one more push on the Render Settings. So let's go back into Maya. This time we're going to set Minimum subdivisions of 5 an Maximum of 16 and, again, if we jump over to Bridge and take a look at our final render. You can see the quality is quite nice indeed.

Line detail looking nice, shadow detail looking nice, not really any discernable noise in the scene, picking out lots of detail in our counter texture. We are though at 27 minutes, which of course is significantly higher than our previous render, but still a long way short of our final Fixed Rate Render. Now, the difference in these two renders is due to the fact that this system is able to be adaptive, whereas the Fixed Rate engine of course is not. Now the DMC System can make intelligent use of the number of samples available to it.

It can focus them on areas of the scene where they're really needed. This means the DMC engine is extremely good at working with noisy render effects; so Motion Blur, Depth of Field, and others, this system can work very nicely with them. Another good thing about the DMC engine is that it is extremely memory efficient. It doesn't hold its sampling information in memory. In terms of weaknesses, there really aren't as such that I would ascribe to the DMC engine, other than the fact that while being able to work adaptively, it is not able to perform any kind of undersampling.

Well, let's move on then and take a look at our final Image Sampling Engine, one that can perform undersampling, and this is the Adaptive Subdivision Engine.

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This video is part of

Image for V-Ray 2.0 for Maya Essential Training
V-Ray 2.0 for Maya Essential Training

54 video lessons · 2214 viewers

Brian Bradley
Author

 
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  1. 4m 28s
    1. Welcome
      59s
    2. What you should know before watching this course
      51s
    3. Exercise files
      40s
    4. Workflow recommendation
      1m 58s
  2. 11m 32s
    1. Installing V-Ray
      4m 25s
    2. Setting up V-Ray
      3m 14s
    3. Locating V-Ray's tools and features
      3m 53s
  3. 24m 41s
    1. Image sampling explained
      3m 19s
    2. Understanding subdivs
      3m 49s
    3. Using the DMC Sampler
      6m 54s
    4. Overview of color mapping
      4m 45s
    5. Understanding the color-mapping modes
      5m 54s
  4. 27m 55s
    1. Dealing with lighting problems
      9m 26s
    2. Adding a spherical fill light
      8m 50s
    3. Creating a mesh light
      2m 43s
    4. Creating a skylight effect
      3m 18s
    5. Working with the dome light
      3m 38s
  5. 44m 25s
    1. Global illumination (GI) explained
      3m 55s
    2. Understanding primary and secondary bounces
      3m 34s
    3. How irradiance mapping works
      5m 30s
    4. Using irradiance mapping, part 1
      4m 35s
    5. Using irradiance mapping, part 2
      5m 44s
    6. How light cache works
      3m 48s
    7. Using light cache
      7m 58s
    8. Understanding brute force GI
      2m 18s
    9. Using brute force GI
      7m 3s
  6. 40m 3s
    1. Introduction to V-Ray-specific materials
      2m 22s
    2. Creating diffuse color
      8m 31s
    3. Making reflective materials
      5m 40s
    4. Blurring reflections
      8m 31s
    5. Making clear and colored glass
      8m 49s
    6. Creating a translucency effect
      6m 10s
  7. 24m 15s
    1. Introduction to image sampling
      2m 56s
    2. Using the Fixed-Rate sampler
      5m 57s
    3. How to use the Adaptive DMC sampler
      5m 21s
    4. Working with the Adaptive Subdivision sampler
      7m 7s
    5. Comparing image-sampling renders
      2m 54s
  8. 17m 23s
    1. The physical workflow explained
      2m 37s
    2. Working with VRaySun and VRaySky
      7m 39s
    3. Controlling the VRayPhysicalCamera
      7m 7s
  9. 45m 0s
    1. Depth of field: VRayPhysicalCamera
      5m 45s
    2. Depth of field: perspective viewport
      5m 49s
    3. Creating a motion blur effect
      9m 30s
    4. Generating caustic effects
      7m 51s
    5. Using VRayFur
      6m 2s
    6. Setting up render-time displacement effects
      10m 3s
  10. 34m 17s
    1. Render elements workflow
      6m 47s
    2. Preparing to composite
      2m 22s
    3. Compositing V-Ray elements
      7m 8s
    4. Putting extra elements to work
      6m 20s
    5. Post-lighting a scene
      11m 40s
  11. 11m 47s
    1. Overview of V-Ray RT
      5m 27s
    2. Demonstrating the RT workflow
      6m 20s
  12. 1m 8s
    1. What's next?
      1m 8s

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