Introduction


 

  • This lesson will take you through additional V-Ray Render Elements that go beyond the basics of the Beauty pass
  • This information centers around how more Advanced Render Elements can be used to control  and refine a final composite
  • The 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 - You will learn about the different utility render elements and how you can use them to create selection masks, or add motion blur, depth of field and ambient occlusion in post processing.

Objective – We will render out several additional Render Elements that can be used to composite with the passes from our Beauty render                         

Outcome – You will understand what a few additional V-Ray Render Elements can be used for to produce a more professional looking final image


Available materials


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

Lesson plan download
Presentation (Lecture) download
Demonstration tutorial download                                                                                          

Scenes & Assets download

 


Lecture



1. Terminology

Advanced Compositing

a) Multiple Matte Passes
  • Unshaded solid color images with red, green and blue colors
  • Each color allows control of selected geometry or materials  the color has been assigned to
b) Ambient Occlusion Pass
  • A shading and rendering technique used to calculate how exposed each point in a scene is to ambient lighting
c) Z-Depth Pass
  • A black and white image which shades an object based on the distance from the camera

  

 

2. Multi Mattes


  • Flat shaded color images where each color channel can be assigned to selected geometry or materials
  • Gives far greater control for color correction and post work by allowing effects to be isolated via the multi matte colors
    • Example: The Blue color can give control over the surfboard material, The Green gives control over the ground’s material and the Red color gives control over the metal material used on the camper
    • ID assignment can be done on objects or materials
  • Each color can be used as a layer mask for objects given that multi matte color

  

 



 


  

  

 

 

Resulting Blue Channel

Original Multi Matte

 

  

The Surf board isolated with the blue channel of the multi matte

  


 

Example of the isolated surf board with No Curves Color Correction

Example of the isolated surf board with Curves Color Correction

 


3. Ambient Occlusion

  • Ambient occlusion is a shading and rendering technique used to calculate how exposed each point in a scene is to ambient lighting
  • The closer two surfaces are together the darker the color will be, the further away the lighter they will be until they are completely White
  • It is a very crude approximation to full global illumination. The appearance achieved by ambient occlusion alone is similar to the way an object might appear on an overcast day.
  • A blend mode of Multiply is used so that only the non White areas contribute to the composite

  

  

 

Composite without Ambient Occlusion

Composite with Ambient Occlusion

 


  • Ambient occlusion can be color corrected using any color correction effects
  • This can be used to simulate other colors and if the original Ambient Occlusion Render Element is used as a luma-matte, it can give a basic rust coloring for example
  • When combined with isolation via a multi-matte, different amounts of ambient occlusion can be used for different surfaces

  

 

Ambient Occlusion with no color changes

Ambient Occlusion with color changes

 


3. Z-Depth


  • Z-Depth Render Elements are white-to-black and generally best output as 32-bit images
  • The grey value represents the distance an object is from the camera
  • Objects closer to the camera are blacker, and objects further away will be whiter
  • A Z-Depth pass is used in compositing to create effects such as Depth of Field & atmospheric fog
  • The Z-Depth Render Element itself when usedto control Depth of Field is not visible, but is used as a control layer

 

  

 

Z-Depth without curves adjustment

Z-Depth with curves adjustment

 


  • To use to contribute to atmospheric fog the Z-Depth image should have its channels inverted. In such a case it would use a blend mode of Screen and its opacity level would be changed as needed
  • The amount of contrast between the dark and light values can be altered with color correction curves in composite for finer control

  

An inverted Z-Depth render element for use as an atmospheric pass

  

a) Z-Depth settings at render time
  • Z-Depth is set at render time with the Minimum and Maximum values
  • The Minimum value represents the closest point from the camera
  • The Maximum value represents the furthest point from the camera
  • At render time a Clamp option allows the values to render from completely black to completely white to make best use of the color range within the Z-Depth Render Element

  

 

Without Camera Lens Blur

With Camera Lens Blur

 

4. Velocity


  • The Velocity render element allows you to extract information about the velocity of each point in the scene that can be used to add motion blur in composite
  • They are 32 bit images where color is assigned based on movement in a given frame
  • Anything that is not moving (should a camera be still) is rendered black
  • Motion blur generated from a Velocity render element is not as good as real Motion Blur at render time (but it is far quicker)
  • Vector motion blur is created using X and Y velocity data contained in the red and green channel respectively. For this reason the blue channel can be considered redundant, and can be safely removed.
  • The Velocity render element itself when usedto control Motion Blur is not visible, but is used as a control layer

  

  

The Final Composite

                                                                                                                                                                                                                               

 

Prior to all Compositing work

After all Compositing work

 



Demonstration



Time to see it work!

Watch while I demonstrate how to setup the additional Render Elements in V-Ray to take a final image beyond beauty.

  

                          

 


Activity



Time to do it yourself!

Use the provided scene file to set up the different masks and utility Render Elements

  

  


Dialing in the right values

  • vrayRE_Z_depth
    • Depth White: 2000
  • Camper_Car_Paint_SG
  • Beach_Sand_SG
  • Surf_02_Blend_SG
  • vrayRE_MM_Camper_Ground_Surf
    • Set the Red object ID: 1
    • Set the Green object ID: 2
    • Set the Blue object ID: 3
    • Enable Use material IDs