V-Ray Wrapper Material

Introduction

This lesson will take you through using the Wrapper Material in V-Ray for Maya
The information centers around the VRayMtlWrapper and introduces V-Ray Object Properties and global rendering overrides
This lesson topic is approximately 30 minutes in length
Lesson covers all 3 Learning Cycles for the Lesson Topic – Lecture, Demonstration, and Activity

Overview

Goal - In this lesson you will learn how to set up matte surfaces with V-Ray

Objective – We will incorporate the V-Ray Wrapper Material into our 3D scene.

Outcome - You will be able to apply the VrayMtlWrapper to objects in our scene and understand how to create special overrides in your scene. You will also understand how to use V-Ray Wrapper overrides for better placing a CG object into a live action background.

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

Here’s some terms to be aware of when thinking about the VRayMtlWrapper and render overrides in general:

Matte surface
- Replaces the base material in the MtlWrapper with the scene’s existing background
Environment Override
- Replaces the Maya environment settings with user-selected V-Ray options for a multitude of effects
Object Properties
- New set of V-Ray specific rendering attributes that are assigned to an object directly
- Allows customizable render settings on a per object basis

2. MtlWrapper Overview

Can be used to specify additional surface properties per material
- Can change the behavior of an object in the render (for example, GI receiving and casting, alpha contribution, etc.)
Base Material
- The surface’s intended material
Additional Surface Properties
- Settings used to manipulate GI and Caustic characteristics
Matte Properties
- Settings used to adjust Alpha and Shadow characteristics

These properties are also available by using a VRayObjectProperties node on the object instead (or in tandem with the Material Wrapper)

3. VRayObjectProperties Overview

VROPs can be assigned directly to geometry nodes with additional control
Used to specify additional object attributes and render functions on a per object basis
- Visibility, GI calculation overrides, Shadow Receiving/Casting, etc.
- To add this node to selected object(s), use the command Apply Single (or Multiple) object properties node from the Create > V-Ray menu or the V-Ray shelf

Additional Surface Properties
- Settings used to manipulate GI and Caustic characteristics
Matte Properties
- Settings used to adjust Alpha and Shadow characteristics

4. Render Settings Overrides

You can also create override on a global basis for the scene through Render Settings

Environment section

Override Environment
- Turn On to override the default Maya environment and render with different V-Ray options
- For example, have a different reflection environment than your GI environment
- Useful for using higher resolution maps for crisp reflections and lower resolution for GI calculation

Background texture
- A color or map used as a background during rendering that need not effect GI or reflections, etc.
Show in viewport
- Similar to image plane on a camera

5. Material Wrapper

a) Matte Surface

Makes the material appear as a holdout material, which shows the background, instead of its base material
The Base Material is still used to calculate GI, caustics, reflections, etc. for compositing use but does not appear in the render otherwise

Matte Surface: Off

Matte Surface: On

Alpha Channel

b) Alpha Contribution

Determines the appearance of an object in the alpha channel of the rendered image

- A value of 1.0 means the alpha channel will be derived from the existing transparency of the base material
- A value of 0.0 means the object will not appear in the alpha channel at all and will show the alpha of any objects behind it
- A value of -1.0 means that the transparency of the base material will cut out from any alpha from the objects behind
- Matte objects are typically given an alpha contribution of -1.0 to make sure they cut out of the alpha for compositing use

Alpha Contribution of floor: 1

Alpha Contribution of floor: 0

Alpha Contribution of floor: -1

c) Shadows

Makes shadows visible on the matte surface
Popular use of the Material Wrapper to better integrate CG objects into a live action background

Shadows: Off

Shadows: On

Shadows: On (alpha)

d) Affect alpha

Makes shadows affect the alpha contribution of the matte surface
Areas in perfect shadow will produce white alpha, while completely un-occluded areas will produce black alpha
Note that GI shadows (from skylight) are also computed, however GI shadows on matte objects are not supported by the Irradiance Map and Light Cache GI engines, when used as primary engines

Shadows: On

Affect alpha: Off

Affect alpha: On

Conclusion

a) Matte surface

How we make our background blend with our CG elements

b) Environment Override

Allows you to have different environments considered for the calculation of GI, Reflections and Refractions

c) Object Properties

Instead of global render settings or per material (like the mtlWrapper), settings on a per object basis

Demonstration

Time to see it work!

Watch while I demonstrate how to create and adjust a V-Ray Material Wrapper on a ground plane in our scene.

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:

mtlWrapper for the table surface:

Matte Surface On
Alpha Contribution set to -1
Shadows On
Affect Alpha On

Content

Space Tools