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VRayLightMtl Overview

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

General

Color - this parameter controls the color of the light material.

Color multiplier - a multiplier for the Color.

Example: Default Color and Multiplier Values

Here is a scene rendered with the default VRayLightMtl. These examples demonstrate how the material behaves in V-Ray, and how its parameters influence the look of the final results.

The white plane is a default VRayLightMtl. The teapot is a default VRayMtl with Reflection. The rest is just VRayMtl with diffuse colors.

We are going to render this scene with Default Lights turned off until the end of the example, and no lights will be used in it either.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_3.png

Default Lights - Off.
Multiplier: 1.0
No GI, No lights

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

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_4.png

Multiplier: 50.0
No GI, No lights

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

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_5.png

Multiplier: 1.0
GI: on

As you can see, turning GI on almost didn't change the overall look. That is because of the Multiplier value: 1.0. It acts mainly to self-illuminate the object that has the VRayLightMtl.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_6.png

Multiplier: 5.0
GI: on
2-sided: off

Now you can see that increasing the Multiplier has visibly influenced the scene (shadows also appears).

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_7.png

Multiplier: 5.0
GI: on
2-sided: on

Scene starting to gather more light because 2-sided is on.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_8.png

Multiplier: 10.0
GI: on
2-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.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_9.png

Multiplier: 10.0
GI: on
2-sided: on

The scene starts to gather more light because 2-sided is on, but we also start to get some burnt areas due to Linear type of Color mapping

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_10.png

Multiplier: 30.0
GI: on - default
2-sided: off
Exponential

So, increasing the Multiplier affects the GI more (we have more light), but you can also see that our render is quite splotchy.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_11.png

Multiplier: 30.0
GI: on - default
2-sided: on
Exponential

Scene starting to gather more light because 2-sided is on. Still splotchy GI solution.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_12.png

Multiplier: 30.0
GI: on; 2-sided: off
IR: HSphS: 100
IR: Interp.S: 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.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_13.png

Multiplier: 30.0
GI: on; 2-sided: on
IR: HSphS: 100
IR: Interp.S: 40

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

Example: Texture as Color

This example shows how the Texmap slot is used and how the map determines the Color parameter.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_14.png

Multiplier: 3.0
GI: on; 2-sided: on
IR: HSphS: 100
IR: Interp.S: 40
Exponential

Here, we used a Bitmap in the Texmap slot. The Multiplier is quite low, so only the plane and the reflection on the teapot are visible.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_15.png

Multiplier: 30.0
GI: on; 2-sided: on
IR: HSphS: 100
IR: Interp.S: 40
Exponential

Increasing the Multiplier leads to a much brighter look in the scene. Notice now that the Bitmap is getting closer to appearing white, due to multiplying the (R,G,B) values of the Bitmap.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_16.png

Multiplier: 3.0
GI: on; 2-sided: on
IR: HSphS: 100
IR: Interp.S: 40
Exponential

Here, another Bitmap is assigned to the Texmap slot. Notice that we haven't changed the VRayMtls for the surrounding walls, but the scene looks different from the previous one due to the new Bitmap.

V-Ray 3.0 for Softimage > VRayLightMtl > LightMtl_17.png

Multiplier: 30.0
GI: on; 2-sided: on
IR: HSphS: 100
IR: Interp.S: 40
Exponential

Increasing the Multiplier leads to a much brighter look in the scene. Notice now the Bitmap is getting closer to appearing white, due to multiplying the (R,G,B) values of the Bitmap.

Transparency - a color or texture to use as opacity for the material. Note that making the material less opaque does not affect the intensity of the self-illumination color. This is so that you can create perfectly transparent materials that nevertheless still emit light.

Emit on back side - checking this option makes the object emit light from its back side as well. If this is off, the material is rendered as black on the back sides.

Compensate Exposure - this option is used when rendering with the V-Ray Physical Camera. When enabled the intensity of the material will be adjusted to compensate for the camera exposure.

Options

Material ID

The Material ID group is described here.

Notes

You can use the VRayLightMtl as a light source assigned to an object. Increasing the Value of the color will affect the GI solution and will produce more light. Note that over bright colors may look the same as pure white but the GI results will be different.