Introduction

  • This lesson will take you through using the Light Material in V-Ray for Maya
  • The information centers around the VRayLightMtl node
  • 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 - Develop the look for our toy rocket and strand of starry lights

Objective - We will light a scene with the VRayLightMtl assigned to an object                 

Outcome - You will be able to apply the VrayLightMtl to an object to light the scene and understand how to adjust the settings to create the look you want in your renders

 




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

Not all Lights are Lights, but can be objects with special materials/shaders on them.

Here’s some terms to be aware of when thinking about the VRayLightMtl:

  • Global Illumination – More realistic lighting technique in CG scenes that includes reflected or bounced light from the primary light sources
  • Direct Illumination – Light that comes directly from a source
  • Light Linking – A way in Maya to create a relationship between lights and geometry
  • Opacity – Transparent properties of an object

 

2. Light

  • Light Temperature – Use the Temperature value to create the right mood for your scene with realistic color 

 

 

2. Light Material


a) VRayLightMtl Overview

Generally used to produce self-illuminated surfaces
Color vs. Temperature - Which mode to use depends on what results you want
  • Direct Illumination - Gives the ability to act like an actual light
  • Emit On Back Side - Same as Double Sided for V-Ray Lights
  • Compensate Camera Exposure - Use when rendering to a V-Ray Physical Camera

 

 


b) Multiplier, Color, Temperature
  • Mode: Color – the light’s color is directly specified by the Color value
    • In the Color example to the right, the background looks green because of the yellow material mixing with the blue light in the scene
  • Mode: Temperature – specifies the light color temperature in degrees Kelvin
    • Great for matching real world lighting
  • Color Multiplier – defines the strength of the light

 

 

Color Mode: Color (with yellow Light Color)

Color Mode: Temperature (with Temp. of 2500)

 

 

c) Opacity
  • Uses a texture to affect the transparency of the object through it’s alpha channel
  • Does not work with the option Direct Illumination Enabled

 

 

RGB Channels (with opacity of stars at 0.2)

Alpha Channel (with opacity of stars at 0.2)

 

 

d) Direct Illumination
  • Allows the material to act like a traditional direct light
    • Similar to a Mesh Light
  • Light cut-off threshold -  a threshold for the light intensity, below which the light will not be computed
    • Useful in scenes with many lights, where you want to limit the effect of the lights to some distance around them
    • Larger values cut away more from the light; lower values make the light range larger
    • If you specify 0.0, the light will be calculated for all surfaces
  • Not able to apply Light Linking to objects with LightMtl
    • Because objects with Light Material do not get a light node the way they do with Mesh Light

 

 

Direct Illum On (for stars)

Direct Illum Off (for stars)

 

 

  • Splotches seen in the render are from Global Illumination only
    • Because much of the illumination (including direct) is being generated from the scene’s GI, more noise is added to the render when there’s less light sources emitting photons around the scene

 

Direct Illum Off (for stars)

Direct Illum Off (lighting element)

Direct Illum Off (GI element)

 

  • Render passes can help show you more information about what’s happening in your render
  • Presents a cleaner render than without Direct Illumination

 

Direct Illum On (for stars)

Direct Illum On (lighting element)

Direct Illum On (GI render element)

 

e) Light Material vs. Mesh Light
  • Mesh Light is categorized in the scene as a Light (vrayMeshLightProperties node)
    • Effected objects can be configured with Light Linking
  • Mesh Light has more Options to customize the light’s effect
    • No Decay, Double Sided, Invisible, Affect Diffuse/Specular/Reflections, etc.

 

Conclusion

a) Direct Illumination

  • Not just self-illuminating, but scene illuminating

b) Color Modes

  • Temperature vs. Color                         

c) Opacity

  • Makes objects with lightMtl assigned to them transparent, if Direct Illumination is Off


Demonstration

Time to see it work! 

Watch while I demonstrate how to create and adjust a V-Ray Light Material for our toy rocket and star lights.

Demonstration tutorial

                    

 


Activity

Time to do it yourself!

Now it’s your turn!! Use the provided scene file to recreate the cinematic look as you have seen me demonstrate.

We have also provided a final scene for your reference.

 

    

 


Used values:

  • Stars_Mtl
    • Ramp texture connected to Color through gammaCorrect
    • Color Multiplier – 12
    • Direct Illum – On
  • Rocket – SelfIllum_Mtl
    • VRayMtl with Ramp texture connected to Self-Illumination through gammaCorrect
  • Lens Effects
    • Bloom Effect – On
    • Glare Effect – On