Page Contents

 

Overview


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

 

 

Parameters


 


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 will be 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 will emit light, and the material will render 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 will be 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


The Multipliers rollout menu provides access to the default V-Ray materials' multipliers control.

 

 

Mode – Specifies how textures and colors are blended by the multipliers. 

Multiplier – When set to Multiply, the texture is blended with black color. 
Blend Amount – When Blend Amount is selected, the user-specified color is used for blending. 

Color – Blends between the assigned texture and the mode specific color.  See the Default Color and Multiplier Values example

Intensity – Blends between the assigned texture and the mode specific color. 

Transparency – Blends between the assigned texture and the mode specific color. 

 



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
IR: HSphS: 100
IR: Interp.S: 40
Exponential

 

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
IR: HSphS: 100
IR: Interp.S: 40
Exponential

 

 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
IR: HSphS: 100
IR: Interp.S: 40
Exponential

 

  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
IR: HSphS: 100
IR: Interp.S: 40
Exponential

 

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.

 

 

Material Options


 

 

Can be Overridden – When enabled, the material will be overridden when you enable the override color option in the Global Switches.

Alpha contribution – Determines the appearance of the object in the alpha channel of the rendered image.

Normal (1) – A value of 1.0 means the alpha channel will be derived from the transparency of the material.
Ignore in Alpha (0)   A value of 0.0 means the object will not appear in the alpha channel at all. 
Black Alpha (-1) – A value of -1.0 means that the transparency of the material will cut out from the alpha of the objects behind. 

ID Color – Allows you to specify a color to represent this material in the Material ID VFB render element. 

Cast Shadows – When disabled, all objects with this material applied will not cast shadows.

Only in Secondary – When enabled, objects with this material applied will only appear in reflections and refractions and will not be directly visible to the camera.

 

 

Maps


These determine the various texture maps used by the material.

Bump/Normal Mapping 

 

 

Bump/ Normal Mapping – Enables or disables the bump or normal effect.

Mode/Map – Specifies the map type. 

Bump Map
Local Space Bump 
Normal map 


Advanced Options

 

Normal Map Type – Specifies the normal map type. 

Tangent space
Object space
Screen space
World space 

Delta Scale – Decrease the value of the parameter to sharpen the bump, increase it for more blurry effect of the bump. 

 

Displacement




Displacement – Enables or disables the displacement effect.

Mode/ Map – Specifies the mode in which the displacement will be rendered. 

2D Displacement – Bases the displacement on a texture map that is known in advanced. The displaced surface is rendered as a warped height-field based on that texture map. The actual raytracing of the displaced surface is done in texture space and the result is mapped back into 3D space. The advantage of this method is that it preserves all details in the displacement map. However, it requires the object to have valid texture coordinates. You cannot use this method for 3d procedural textures or other textures that use object or world coordinates. The parameter can take any values. 
Normal Displacement – Takes the original surface geometry and subdivides its triangles into smaller sub-triangles, which then are displaced. 

Amount – The amount of displacement. A value of 0.0 means the object appears unchanged. Higher values produce a greater displacement effect. This parameter can also take a negative value, in which case the displacement will push geometry inside the object. 

Shift – Specifies a constant, which will be added to the displacement map values, effectively shifting the displaced surface up and down along the normals. This can be either positive or negative.

Keep continuity – When enabled, tries to produce a connected surface, without splits, when there are faces from different smoothing groups and/or material IDs. Note that using material IDs is not a very good way to combine displacement maps since V-Ray cannot always guarantee the surface continuity. Use other methods (vertex colors, masks etc) to blend different displacement maps.

View dependent – When enabled, Edge length determines the maximum length of a subtriangle edge in pixels. A value of 1.0 means that the longest edge of each subtriangle will be about one pixel long when projected on the screen. When disabled, Edge length is the maximum sub-triangle edge length in world units.

Edge length – Determines the quality of the displacement. Each triangle of the original mesh is subdivided into a number of subtriangles. More subtriangles mean more detail in the displacement, slower rendering times and more RAM usage. Less subtriangles mean less detail, faster rendering and less RAM. The meaning of Edge length depends on the View dependent parameter. 

Max subdivs – Controls the maximum sub-triangles generated from any triangle of the original mesh when the displacement type is Subdivision. The value is in fact the square root of the maximum number of subtriangles. For example, a value of 256 means that at most 256 x 256 = 65536 subtriangles will be generated for any given original triangle. It is not a good idea to keep this value very high. If you need to use higher values, it will be better to tessellate the original mesh itself into smaller triangles instead. The actual subdivisions for a triangle are rounded up to the nearest power of two (this makes it easier to avoid gaps because of different tessellation on neighboring triangles). 

Water Level – Clips the surface geometry in places where the displacement map value is below the specified threshold. This can be used for clip mapping a displacement map value below which geometry will be clipped. 

Level Height – Value below which the geometry is clipped. 

 

 

Environment Overrides


Allows Background, Reflection, and Refraction maps from Environment Settings to be overridden for the current material.

 

 

 

Background Environment

Texture – Specifies a texture to be used as the overriding map.

Multiplier – Specifies a multiplier for the overriding map.

Reflection Environment

Texture – Specifies a texture to be used as the overriding map.

Multiplier – Specifies a multiplier for the overriding map.

Refraction Environment

Texture – Specifies a texture to be used as the overriding map.

Multiplier – Specifies a multiplier for the overriding map.

 

Notes


  • You can use the BRDFLight 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 overbright 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 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.