Introduction


  • This lesson will take you through creating a quick Global Illumination for Interior scenes
  • The information centers around Global Illumination render settings
  • This lesson topic is approximately 30 minutes in length
  • Lesson covers all 3 Learning Cycles for the Lesson Topic – Lecture, Demonstration, and Activity

Contents


Overview
Available Materials
Lecture
Demonstration
Activity                                   


Overview


Goal – In this lesson you will learn how properly set up the GI for interior scenes in order to optimize quality and render times.

Objective – We will learn how to add Global Illumination to an interior scene and how to optimize your render results and render times                                            

Outcome – You will be able to add GI to your interior scenes and know the basics of tweaking settings depending on what is important for your scene

 


 


Available materials


To set up the lesson follow the links below and download all available materials.

Lesson plan download
Presentation (Lecture) download
Demonstration tutorial 1 download                                          
Demonstration tutorial 2 download
Scenes & Assets download

 

Lecture



1. Terminology

When we see things in the real world they are illuminated both directly and indirectly. Here’s some terms to be aware of when thinking about Global Illumination

  • Indirect Lighting - When light bounces around and fills in areas that a direct light source can not reach
  • Anti-Aliasing - A method of smoothing the edges of render objects to improve the quality of the image
  • Image Sampler - An algorithm for sampling and filtering the pixels in your render
  • Bounce Engine - The type of calculations used to render the Global Illumination of our V-Ray scene

2. Occlusion

Light doesn’t naturally fall evenly over every part of a surface

  • Some areas remain in shadow, unless directly illuminated by a source
  • Having these darker areas in the corners of our 3D renders can help them feel more real

 

3. Global Illumination

a) V-Ray Quick Settings

  • The V-Ray Quick Settings dialog is an easy way to control the most common aspects of the renderer and to quickly switch between different GI solutions and quality settings
    • It is also intended to give new V-Ray users the ability to set up scenes without worrying about all the different V-Ray options available in the Render Setup dialog
    • Presets help give a good starting point depending on the type of scene

 

 

The ArchViz Interior preset is useful for indoor scenes where light bounces are important

  • The Manage Presets allows you to save the current settings into the V-Ray presets file or to load a previously saved settings
  • The Settings buttons give you a quick way to jump to the render settings that apply to the area affected by the Quality sliders (GI, Shading, Anti-Aliasing)

 To open Quick Settings, click its icon in the V-Ray shelf (shown below)

  • If you do not have the V-Ray shelf, enable it through the Render Settings window, Vray tab under the Vray UI heading by clicking Create/Replace V-Ray Shelf

 

 

 

 

b) Render Elements
  • The info that can be seen by different Render Elements can help us understand more about what’s calculated in that part of the render
  • GI – the diffuse surface global illumination (or indirect lighting)
  • Lighting – the diffuse direct surface lighting

 

 

  • Breaking out the direct and indirect lighting can help see what areas are contributing to the final result

 

 

 

Lighting Render Element

GI Render Element

 

 

c) V-Ray Quick Settings GI Quality
  • With the BF + LC (accurate) Preset selected, the GI Quality slider adjusts the Brute force and Light Cache Subdivs, the Light Cache’s  Prefilter samples, and the Light Cache’s Retrace threshold, which are all used when calculating the indirect illumination
    • The other GI presets can be used to change the bounce engines used in the GI calculation of the render
    • BF + BF is more accurate than BF + LC, but is the slowest to render

 

Rendered with default values (IM + LC (fast)) and Quick Settings

 


d) Quick Settings
  • GI Presets (the chosen bounce engines) not only make a difference in the render quality but also in the time it takes to render
  • Difference in quality is best seen on the back wall

 

 

BF + LC (accurate) at 75%  Render Time: 7min 55sec

IM + LC (fast) at 75%  Render Time: 2min 30sec

 

 

e) V-Ray Quick Settings AA Quality
The Anti-Aliasing Quality slider adjusts the Image Sampler’s Min Subdivs, Max Subdivs, and Noise Threshold
  • Min Subdivs determines the initial (minimum) number of samples taken for each pixel
    • You will rarely need to set this to more than 1, except if you have very thin lines that are not captured correctly, or fast moving objects if you use motion blur
    • The actual number of samples is the square of this number (e.g. 4 subdivs produce 16 samples per pixel)
  • Max Subdivs determines the maximum number of samples for a pixel
    • The actual maximum number of samples is the square of this number (e.g. 4 subdivs produces a maximum of 16 samples)
    • Note that V-Ray may take less than the maximum number of samples, if the difference in intensity of the neighboring pixels is small enough

 

 


 

 


f) Adaptive Image sampler

  • The noise Threshold is the range limit used to determine if a pixel needs more samples
  • The AA Slider Limit from the Quick Settings adjusts the overall AA quality (seen here in the Render Globals) to try to help speed up render times

 

 

 

g) Light Cache Subdivs
  • Controls the number of rays that are shot into the scene, and the "noise" quality of the light cache samples
    • The actual number of paths is the square of the subdivs (the default 500 subdivs mean that 250 000 paths will be traced from the camera)
    • As you add more samples, the noise in the render is reduced but the render times will increase

 

 


h) Skylight portals
  • A way to create more accurate GI by helping the calculations from an exterior light source by adding area lights to help bounce GI through windows
  • When checked On, the vrayRectLight will sample Color and Intensity information from the environment behind it, ignoring it’s Color and Multiplier parameters

 


 

  • GI from Skylight portals is easier to see when the Sun is not directly illuminating the interior scene
  • If there’s geometry behind the Portals, they will be sampled and can slow down the render
    • Turning On Simple Skylight Portal will not sample geometry behind the rectLight

 

 

V-Ray Sun pointing opposite of windows

V-Ray Sun with Skylight Portals; contact shadows a little stronger

 

 

 
i) Saving Light caches and Irradiance Maps
  • Much of the calculation time rendering with GI is spent figuring out how the rays bounce around the scene
  • The GI can be calculated once and reused if there are no major changes
  • Very useful for computing the maps/caches and then moving the camera to an area where the GI is already calculated or for fly-through animations

 

Render Time: 2min 15sec when calculating GI
Render Time: 14sec when loading GI from a Saved File


 

  

 


Conclusion



a) Indirect Lighting

  • Illumination caused by light rays bouncing off objects in the scene

b) Anti-Aliasing

  • A function used to produce cleaner renders by blurring the edges of an object with pixels in the background

c) Image Sampler

  • A group of settings that help set up the correct Anti-Aliasing settings for your scene

d) Bounce Engine                        

  • Makes a big difference in the speed and accuracy of the Global Illumination rendering of our scenes

 


Demonstration



Time to see it work! 

Watch while I demonstrate how to adjust the GI settings of our render from the V-Ray Quick Settings and the GI section of the Maya Render Settings window and then proceed to a demo of light portals and how they are used with GI.
Demonstration tutorial 1                             
Demonstration tutorial 2

 

                               
 

Activity



Time to do it yourself!

Use the provided scene file to setup GI in the interior scene of the kid’s bedroom
We have also provided a final scene for your reference.

 

 

Dialing in the right values:
  • GI Quality at 75%
    • IM subdivs: 100
    • LC subdivs: 1500 (override quick settings)
    • LC Prefilter: 20
    • LC Retrace: 5
  • Shading Quality at 3%
    • Min Shading Rate: 2
  • AA Quality at 29%
    • Adaptive Min subdivs: 1
    • Max subdivs: 8
    • (noise) Threshold: 0.005