This page provides information about the Emissive material in V-Ray for Revit.
Overview
The Generic V-Ray material's preset Emissive is generally used for producing self-illuminated surfaces.
Emissive
Some options are available only in Advanced mode.
Color – Specifies the color of the light. A texture can be specified as well. For more information, see the Textures example below.
Intensity – Controls the strength of the light.
Transparency – Specifies the color that is transparent. A texture can be specified as well.
Emit On Back Side – When enabled, the object emits light from its back side as well. When disabled, only the front side emits light, and the material renders as black on the back sides. For more information, see the Higher Multiplier/2-Sided On and Off example below.
Compensate EV – Used when rendering with the V-Ray Physical Camera. When enabled, the intensity of the material is adjusted to compensate for the camera exposure.
Color *Opacity – When enabled, the color of the light material is multiplied by the opacity texture. Otherwise, the color and opacity act independently (so-called additive transparency).
Multipliers
This rollout is available only in Advanced mode.
Mode – Specifies one of the following methods for adjusting textures.
Multiply – Multipliers can be specified to adjust colors and textures.
Blend Amount – Blend amounts can be specified to adjust colors and textures.
Color – Controls the intensity of the Emissive Color (light color). See the Default Color and Multiplier Values example.
Intensity – Controls the strength of the light.
Transparency – Controls the intensity of the Transparency Color, which determines the color that is transparent.
Example: Textures
This example shows using the BRDFLight with a texture in the Color slot. In order to control the strength of the light we will need to adjust the Value of the Color Multiplier parameter in the Color Balance roll out of the texture.
Color Multiplier: 3.0
GI on ;
Emit on Back Side on
Using a File texture connected to the Color slot. The Color Multiplier is quite low, so only the plane and the reflection on the teapot are visible.
Color Multiplier: 15.0
GI on ;
Emit on Back Side on
Increasing the Color Multiplier leads to a much lighter overlook of the scene. Notice that now the texture is getting closer to white color look, due to multiplying the (R,G,B) values of the texture.
Color Multiplier: 3.0
GI on ;
Emit on Back Side on
Here is another File texture connected to the Color 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 texture.
Color Multiplier: 15.0
GI on ;
Emit on Back Side on
Increasing the Color Multiplier leads to a much lighter overlook of the scene. Notice now that the texture is getting closer to white color look, due to multiplying the (R,G,B) values of the texture.
Example: Default Color and Multiplier Values
Here is a scene rendered with the default BRDFLight. These examples demonstrate how the material behaves in V-Ray, and how its parameters influence the overlook of the final results.
The white plane is a default BRDFLight. The teapot is a default VRayMtl with Reflection. Rest is just VRayMtl with diffuse colors.
We are going to render this scene with Default Lights - Off till the end of the example and no lights will be used in it as well.
Color value: 1.0
No GI
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 totally expected and reasonable.
Color value: 50.0
No GI
Notice that nothing changed in general, BUT the reflection on the teapot got stronger due to the higher color value. Rest is still black: because we still have the GI off.
Color value: 1.0
GI on
As You see turning GI on almost didn't change the overlook. That is because of the Color value: 1.0. It acts mainly as just self-illuminating the object that has the BRDFLight.
Example: Higher Multipliers/2-Sided On and Off
Color value: 5.0
GI on
Emit on Back Side off
Now you can notice that increasing the Color value has influenced visibly the scene (shadows also appear).
Color value: 5.0
GI on
Emit on Back Side on
Scene starting to gather more light because of the 2-sided - on.
Color value: 15.0
GI on
Emit on Back Side off
As you see the back is still dark, but You can already notice the blue wall receiving some GI, due to higher Color value. Shadows also appear more defined.
Color value: 15.0
GI on
Emit on Back Side on
Scene starting to gather more light because of the 2-sided - on.
For all other material settings, see the Attributes section on Materials page.
Notes
- You can use the BRDFLight as a light source assigned to an object. Increasing the Value of the color affects the GI solution and produces more light. Note that overbright colors may look the same as pure white but the GI results is 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 multiplier for BRDFLight 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 BRDFLight material is the only material applied on the object. They will not work if the material is part of a complex material like a VRayBlendMtl material. This restriction will probably be removed in a future release.