Table of Contents

This page provides information on the Wrapper Material.


The VRayMtlWrapper can be used to specify additional surface properties per material. These properties are also available in the Object properties dialog. However, the settings from the VRayMtlWrapper override those from the Object properties.

VRayMtlWrapper Parameters

Base material – Specifies the actual surface material.

Additional Surface Properties

Generate GI – Controls the GI generated by the material.

Receive GI – Controls the GI received by the material.

Generate caustics – When enabled, this material generates caustics.

Receive caustics – When enabled, this material recieves caustics.

Matte Properties

Matte surface – Makes the material appear as a matte material, which shows the background instead of the base material when viewed directly. Note that the base material is still used for things like GI, caustics, reflections, etc.

Alpha contribution – Determines the appearance of the object in the alpha channel of the rendered image. A value of 1.0 means the alpha channel is derived from the transparency of the base material. A value of 0.0 means the object does not appear in the alpha channel at all and shows the alpha of the objects behind it. A value of -1.0 means that the transparency of the base material cuts out from the alpha of the objects behind. Matte objects are typically given an alpha contribution of -1.0. Note that this option is independent of the Matte surface option (i.e. a surface can have an alpha contribution of -1.0 without being a matte surface).

Matte for refl/refr – Makes the material appear as a matte material, which shows the background instead of the base material when viewed through reflections and/or refractions.

Shadows – When enabled, makes shadows visible on the matte surface.

Affect alpha – When enabled, shadows affect the alpha contribution of the matte surface. Areas in perfect shadow produce white alpha, while completely unoccluded areas produce black alpha. Note that GI shadows (from skylight) are also computed, however GI shadows on matte objects are not supported by the photon map and the light map GI engines, when used as primary engines. You can safely use those with matte surfaces as secondary engines.

Color – Specifies an optional tint for the shadows on the matte surface.

Brightness – Specifies an optional brightness parameter for the shadows on the matte surface. A value of 0.0 makes the shadows completely invisible, while a value of 1.0 shows the full shadows.

Reflection amount – Shows the reflections from the base material. This only works if the base material is directly a VRayMtl.

GI amount – Determines the amount of GI shadows.

No GI on other mattes – Causes the object to appear as a matte object in reflections, refractions, GI, etc. for other matte objects. Note that if this is enabled, refractions for the matte object might not be calculated (the object will appear as a matte object to itself and will not be able to "see" the refractions on the other side).


GI surface ID – Used to prevent the blending of light cache samples across different surfaces. If two objects have different GI surface IDs, the light cache samples of the two objects will not be blended. This can be useful to prevent light leaks between objects of vastly different illumination.


  • When creating a matte object with VRayMtlWrapper and using the V-Ray CUDA engine, please note the following:
    • Alpha Contribution should be set to -1.0;
    • The Matte Surface, Affect Alpha and Shadows options should be enabled.
  • In V-Ray 5, matte objects always show the background. Since V-Ray 6, however, the matte objects show the V-Ray Dome light instead of the background when a V-Ray Dome light is present in the scene.