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Image sampling explained

From: V-Ray 2.0 for Maya Essential Training

Video: Image sampling explained

When working with a ray-trace rendering engine such as V-Ray, there are certain core fundamentals of ray-tracing technology that we, or more specifically, our work, will benefit from understanding. The five videos in this chapter will help us understand some critical rendering concepts as they apply to the V-Ray renderer. Specifically, we will look at image sampling, subdivisions, the DMC sampler, and color mapping. In this particular video, we are going to focus for a few minutes on our first concept there; that of image sampling.

Image sampling explained

When working with a ray-trace rendering engine such as V-Ray, there are certain core fundamentals of ray-tracing technology that we, or more specifically, our work, will benefit from understanding. The five videos in this chapter will help us understand some critical rendering concepts as they apply to the V-Ray renderer. Specifically, we will look at image sampling, subdivisions, the DMC sampler, and color mapping. In this particular video, we are going to focus for a few minutes on our first concept there; that of image sampling.

The natural question to start with, of course, would be, what is image sampling? When we talk about the image sampling process, we are really talking about the ray-trace rendering process itself; that is, the process of constructing a final rendered 2D image from the information collected out of our authored 3D environment. In order to collect all of the relevant information found in that environment -- that is geometric shapes, material types, light, and shadow values, etcetera -- our ray-trace renderer needs to sample the scene, so that it can determine what color value should be drawn in each of the pixels making up our final rendered image.

The million dollar question, of course, is, how is this sampling, or gathering of information accomplished? Well, this is where we need to dig a little bit into the basic workings of ray-trace rendering. The process, generally speaking, goes a little like this. From the rendering camera's point of view, a number of rays are cast or shot through each of the pixels making up our rendered frame window, and they are sent out into our 3D environment. These are called primary rays, sometimes referred to as eye or camera rays, as they are cast from the rendering point of view.

They are sent out to sample, or gather information from the objects that can be found, in the rendering camera's field of view. As these rays hit, or come into contact with geometric surfaces, they take note of, and collect a wide range of information, such as diffused color values, reflectivity, and so on. They also send out shadow rays, whose job it is to check whether or not a given point on the surface of an object is to be rendered in direct light or in shadow. At this point, our primary rays will also make an evaluation as to whether or not secondary, or bounced rays, are required.

These are needed when properties such as reflection and/or refraction are found in the scene. Once the user specified amount of sampling or information gathering has been accomplished, the collected data is returned back along each ray's traveled path, fed into the renderer for evaluation, and then drawn as a final pixel color value. Of course, this is an extremely simplified overview of what is, in reality, an incredibly complex process, that can potentially involve millions of different kinds of rays being cast and traced through our scenes in order to produce a final image for us.

Well, this simple overview is enough for us to work with in this course. It will really help us when we take a look, a little later on, at V-Ray's image sampling engines themselves, and indeed, it is enough for us to be able to move on to our second critical concept video, which will deal with the topic of subdivs, or subdivisions in V-Ray.

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

54 video lessons · 2244 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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