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Primary and secondary bounces

From: Learning V-Ray for Maya: A Professional Reference Guide

Video: Primary and secondary bounces

In this video, we'll be taking a deeper look into global illumination with VRay, as far as primary and secondary bounces. We're going to go ahead and open the scene file giscene001, that's available to you through this video. And taking a look in the scene, we've got a simple geometry setup with a box with a little sculpture next to it and a glass cylinder out in front.

Primary and secondary bounces

In this video, we'll be taking a deeper look into global illumination with VRay, as far as primary and secondary bounces. We're going to go ahead and open the scene file giscene001, that's available to you through this video. And taking a look in the scene, we've got a simple geometry setup with a box with a little sculpture next to it and a glass cylinder out in front.

We have a blue wall inside, and a green ceiling inside that box, as well as a red backing to our little stepped structure. The whole scene is lit by a single V-Ray light that is enclosed inside a sphere which right now is only one sided. So we can see into this sphere from the outside since global illumination is all about light bouncing we've decided to enclose the entire sphere to allow the light to bounce around inside the scene. In the Render Settings dialog, we'll see that the indirect illumination tab shows that GI, is by default turned off.

We are using a 2.2 gamma where don't affect colors is turned on. And we are also using The V-Ray vfb as well while it is set to SRGV view mode. We'll go ahead with gi turned off. We'll render the camera that is called Render Cam, and see what it looks like with only direct lighting involved.

And as you can see, we have very dark areas where the shadows are. Indeed, because of the single light source, there is no direct light reaching into our little box, nor into our structure on the side. We'll go ahead in the render settings window and turn on GI. We will leave reflected and refractive caustics turned off for the moment and we'll leave everything to its default. Meaning we have a primary balance of irradiance map. However for the secondary bounce, we'll go ahead and set that to none to turn off the secondary bounce.

So with this render we're only getting a primary bounce of light. This is the calculation phase that goes through the light from the radiance map. And this is our result, you can start to see light bouncing around inside our room and inside our structure. Comparing with our previous render, in the history, you can start to see how A primary bounce starts filling in some of these enclosed areas. This has helped in part by the fact that we have and overall dome or sphere that encompasses the entire scene, allowing more of the light to be captured throughout the scene.

Well we can see here, now, adding a secondary balance will increase the overall illumination in our scene. So, let's go ahead and set our secondary bounce engine to Brute Force. With everything else set to default we'll go ahead and rerender This frame. They'll begin to see that there's an increase in illumination inside the box as well as inside the enclosure during the irradiance map calculation. And as we finish the render and compare it with the previous render in our history you can see the secondary bounce has added quite a bit of illumination to our scene. Its a matter of fact looking inside the box you will see that the secondary bounce has also picked up color bleed coming up from green. Ceiling to the side of our wall.

Now lets go into the render setting and turn on reflective and refractive acoustics. So we have primary bounce of radiant map secondary bounce of blue force and both types of acoustics turned on rendering will allow us to see a little bit of additional light play around where the glass reflective object is showing us a reflective acoustic. Seen in the increasing illumination right here, as well as a refractive caustics shown right here.

Comparing the two, before caustics and after caustics shows you also a slightly increased level of illumination reflecting from the glass cylinder. (SOUND) Different combinations of bounce engines will yield slightly different results with different render times. Getting a proper combination will depend on the scene itself, the objects in the scene and the animation as far as the objects and the camera in this scene. In this video we took a lot at what primary and secondary bounces are, inside a VRay, and how to enable them as well as reflective and refractive caustics.

Show transcript

This video is part of

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  1. 2m 1s
    1. Welcome
      2m 1s
  2. 9m 42s
    1. What is V-Ray?
      2m 50s
    2. V-Ray integration with the Maya UI
      6m 52s
  3. 1h 0m
    1. The Rectangle light
      11m 8s
    2. The Sphere light
      9m 24s
    3. The Dome light
      4m 52s
    4. V-Ray Sun and Sky
      11m 7s
    5. Using images and HDRs on lights
      8m 35s
    6. Using linear color space and the V-Ray Frame Buffer
      15m 20s
  4. 39m 58s
    1. The V-Ray material
      12m 46s
    2. The V-Ray Blend material
      6m 42s
    3. The V-Ray Light material
      6m 14s
    4. The V-Ray Car Paint material
      8m 21s
    5. V-Ray textures: Dirt for ambient occlusion and edges
      5m 55s
  5. 52m 21s
    1. What is global illumination (GI) in V-Ray?
      2m 43s
    2. Primary and secondary bounces
      5m 58s
    3. Brute force
      9m 1s
    4. Light caching
      11m 49s
    5. Irradiance mapping
      9m 50s
    6. Popular GI engine combinations
      13m 0s
  6. 30m 33s
    1. What are V-Ray object properties (VROPs)?
      2m 47s
    2. Creating VROPs
      9m 8s
    3. Extra object properties
      7m 48s
    4. Material IDs vs. object IDs
      5m 8s
    5. Setting VROP overrides with Maya layers
      5m 42s
  7. 40m 10s
    1. Creating passes and elements
      6m 23s
    2. Diffuse, reflection, and refraction
      8m 49s
    3. Lighting and GI
      4m 3s
    4. Shadows
      5m 6s
    5. Ambient occlusion
      8m 39s
    6. The Multi Matte render element
      7m 10s
  8. 57m 0s
    1. Cameras
      8m 32s
    2. Using the V-Ray Frame Buffer and history
      10m 22s
    3. General V-Ray render settings
      8m 57s
    4. Sampling settings
      12m 1s
    5. Color mapping
      6m 0s
    6. Surface subdivision rendering
      3m 43s
    7. Back to beauty: Assembling the render
      7m 25s

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