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 Please note that this documentation space offers information for V-Ray 3.6! For most up-to-date documentation, refer to V-Ray Next for Modo help.

This page provides information on the V-Ray Light Material.

 

Page Contents

 

Overview  


The V-Ray Light Mtl is a special material provided with the V-Ray renderer. This material is generally used for producing self-illuminated surfaces.

 

 

 


 

UI Path: |Shading viewport| > Shader Tree > Add Layer button > V-Ray Materials > V-Ray Light Mtl


Parameters  





Light Color – The self-illumination color of the material. 

Color multiplier – Multiplier for the Light Color. Note that this does not affect the texture map, if specified.

Transparency – A texture to use as transparency for the material. Note that making the material less opaque does not affect the intensity of the self-illumination color. You can create perfectly transparent materials that nevertheless still emit light.

V-Ray Light Mtl supports color transparency, thus it uses the "color" output of textures rather than their "mono" output.

Double sided – When enabled, the material will be rendered on back-facing polygons as well.

Emit light on back side – When disabled, the material is rendered as black on the back sides.

Compensate exposure – When enabled, the intensity of the light material will be adjusted to compensate the exposure correction from the V-Ray Physical Camera.

Multiply by opacity – When enabled, the color of the light material is multiplied by the opacity texture. Otherwise, the color and opacity act independently to produce the so-called additive transparency.

Affect GI – When enabled, the light emission affects GI rays and illuminates the scene.

 

 



Example: Light Color and Color Multiplier Values


For the examples below, the interior cube is the default V-Ray Light Mtl. The exterior cube is a default V-Ray Material with Reflection. The rest of the scene is shaded with a basic diffuse V-Ray Material.

This scene is rendered without any direct light sources.

 

 


Color multiplier: 1.0
No exposure compensation
No GI

As you see, the image is absolutely dark except the cube (self-illuminated) and the reflection on the floor and exterior cube. Notice we have no GI and no lights at all here, so the dark part of the scene is to be expected.

 


Color multiplier: 1.0
Exposure Compensation
No GI

Notice that the cube appears brighter due to the exposure compensation. The rest is still black because we still have the GI off.

 


Color multiplier: 50.0
No exposure compensation
No GI

Notice that nothing changed in general, BUT the reflection on the floor and outer cube got stronger due to higher multiplier. The rest is still black because we still have the GI off.

 


Color multiplier: 50.0
Exposure compensation
No GI

Once again, the cube and reflections are brighter due to the exposure compensation.

 

 

 

 

This example shows how the Light Color is used with a texture and how the map determines the Color parameter.

 

 


Color multiplier: 3.0
GI: on; Double sided: on
Irradiance map Subdiv: 100
Irradiance map Interp. samples: 40
Exponential

Here, we used an Image map for the Light color channel. The Color multiplier is quite low, so only the plane and the reflection on the teapot are visible.

 


Color multiplier: 30.0
GI: on; Double sided: on
Irradiance map Subdiv: 100
Irradiance map Interp. samples: 40
Exponential

Increasing the  Color multiplier leads to a much brighter look in the scene. Notice now that the Image map is getting closer to appearing white, due to multiplying its (R,G,B) values.

 


Color multiplier: 3.0
GI: on; Double sided: on
Irradiance map Subdiv: 100
Irradiance map Interp. samples: 40
Exponential

Here, another Image map is assigned to the Light color channel. Notice that we haven't changed the materials for the surrounding walls, but the scene looks different from the previous one due to the new Image map.

 


Color multiplier: 30.0
GI: on; Double sided: on
Irradiance map Subdiv: 100
Irradiance map Interp. samples: 40
Exponential

Increasing the Color multiplier leads to a much brighter look in the scene. Notice now the Image map is getting closer to appearing white, due to multiplying its (R,G,B) values.

 

 

 

 

 


 

Example: Image map

 

 


Color multiplier: 30.0
GI: on
Double sided: off
Exponential

Increasing the Multiplier affects the GI more (we have more light), but the render is splotchy.

 


Color multiplier: 30.0
GI: on; Double sided: off
Irradiance map Subdivs: 100
Irradiance map Interp. samples: 40

Comparing this result to the previous, the new render looks much better. The GI solution is clearer, and shadows are more precise. Of course, this leads to higher render time.

 

 

 



Example: Two Sided

 


In the examples below, the V-Ray Light Mtl is applied to the curved plane.

 

 

 

Color multiplier: 1.0
GI: on
Double sided: off

Increasing the multiplier visibly influences the scene. Shadows appear.

 

Color multiplier: 1.0
GI: on
Double sided: on

Scene starts to gather more light due to Double Sided being activated.

 


Color multiplier: 5.0
GI: on
Double sided: off

As you can see, the back is still dark, but you can already notice the blue wall receiving some GI, due to a higher Multiplier. Shadows also appears more defined.

 


Color multiplier: 5.0
GI: on
Double sided: on

The scene starts to gather more light because  Double sided is on, but we also start to get some burnt areas due to Linear type of Color mapping


 

 

V-Ray Mtl Common


The V-Ray Mtl Common tab includes rollouts like Layer and Bump and Displacement, which includes settings that are general among many V-Ray (and Modo) Materials. For more details, please see the Common V-Ray Material Attributes page.

 

Notes


  • You can use the V-Ray Light Mtl as a light source assigned to an object. Increasing the Color multiplier will affect the GI solution and will produce more light. Note that overly bright colors may look the same as pure white but the GI results will be different.
  • If you know the photometric power of a self-illuminated object in lumens (e.g. 1700 lm for a 100-watt bulb) you can calculate the Color multiplier for V-Ray Light Mtl if you divide the lumens by the surface area of the object in meters, provided that the self-illuminated color is pure white.
  • The direct illumination options currently only work properly if the V-Ray Light Mtl material is the only material applied on the object. They will not work if the material is part of a complex material like V-Ray Blend Mtl material. This restriction will probably be removed in a future release.