Table of Contents

This page provides information on the Globals rollout under the Globals tab in V-Ray's Render Settings.


Overview


 The Globals rollout allows you to control some of V-Ray's features globally so as to quickly debug your scene.

UI Path


 

||Properties Editor|| > Render > Globals tab > Globals rollout

 

Parameters


 

Geometry


 Force back face culling - Enables or disables (default) back face culling for camera and shadow rays. When this option is on, the surfaces of objects which are turned away from the camera (or the light source, when tracing shadows) appear fully transparent. This allows you to look inside closed objects when the camera is outside.

Secondary ray bias - A small positive offset that is applied to all secondary rays. This can be used if you have overlapping faces in the scene to avoid the black splotches that may appear.


Lighting


Use lights – Enables or disables lights globally. Please note that if you uncheck this, V-Ray uses default lights. If you do not want any direct lighting in your scene, you must uncheck both this and the Default lights parameters.

Use default lights – Enables or disables the default lights in the scene.

Disable self-illumination – When enabled self-illuminated materials is disabled.

Use hidden lights – Enables or disables the usage of hidden lights. When this is checked, lights are rendered regardless of whether they are hidden or not. When this option is off, any lights that are hidden for any reason (either explicitly or by type) are not included in the rendering.

Shadows – Enables or disables shadows globally.

Show GI only – When this option is on, direct lighting will not be included in the final rendering. Note that lights will still be considered for GI calculations, however in the end only the indirect lighting will be shown.

Lights evaluation mode  Determines how lights are sampled in scenes with many lights.

Adaptive Lights  Uses information from the Light cache to determine which lights to sample. If a Light cache is not used, uniform sampling will be used. Depending on the scene, it can be faster than the Full lights evaluation and Uniform probabilistic lights mode.

Uniform Probabilistic Lights  V-Ray randomly chooses the specified number of lights and evaluates only those. Lower values make the rendering faster, but potentially more noisy. Higher values cause more lights to be computed at each shading point, thus producing less noise, but increasing render times. This option makes it possible to render images that would otherwise take a very long time, at the expense of possibly introducing more noise into the rendering. When GPU rendering, this will introduce probabilistic light calculations. Previous V-Ray 3 scenes that had the Probabilistic Lights parameter enabled, will default to using this option. 
Full Lights Evaluation  V-Ray goes through each scene light and evaluates it at each shading point. In scenes with many lights and lots of GI bounces, this leads to a lot of shadow rays being traced and rendering can become extremely slow. When GPU rendering, this will introduce probabilistic light calculations but will not allow the Number of prob. lights to be set. Older V-Ray scenes with the Probabilistic Lights parameter disabled will default to using this option.  For more information, see The Probabilistic Lights example below. 


GI


 Clamp max ray intensity – Suppresses the contribution of very bright rays, which may typically cause excessive noise (fireflies) in the rendered image. Its effect is similar to the Subpixel mapping + Clamp output options of the Color mapping section, but the Max ray intensity is applied to all secondary (GI/reflection/refraction) rays, as opposed to the final image samples. This allows fireflies to be effectively suppressed but without losing too much HDR information in the final image. Similar to the Subpixel mapping option, the Max ray intensity introduces bias in the rendered image, as it may turn out to be darker than the actual correct result.

GI texture filtering multiplier – A multiplier for the filtering of textures when calculating GI.


Materials


Override material –  Allows the user to override the scene materials when rendering. All objects will be rendered with the chosen material, if one is selected, or with their default wireframe materials if no material is specified.

Maps – Enables or disables texture maps.

Filter maps – Enables or disables texture map filtering. When enabled, the depth is controlled locally by the settings of the texture maps. When disabled, no filtering is performed.

Filter maps for glossy/GI rays – Enable or disable texture filtering during GI calculations and glossy reflections/refractions. When off (the default), texture maps are not filtered for GI and glossy reflections/refractions in order to speed up the calculations. If this option is on, textures will be filtered in these cases.

Max transparency levels – The depth to which transparent objects will be traced.

Reflection / Refraction – Enables or disables the calculation of reflections and refractions in V-Ray maps and materials.

Use global max depth – Enables the user to limit globally the reflection/refraction depth. When this is unchecked, the depth is controlled locally by the materials/maps. When this option is checked, all materials and maps use the depth specified here.

Glossy effects  Allows the user to replace all glossy reflections in the scene with non-glossy ones; useful for test renderings.

Uninverted normal bump – When enabled the normal bump in tangent space will not be inverted on flipped UVs.

Transparency cutoff – Controls when tracing of transparent objects will be stopped. If the accumulated transparency of a ray is below this threshold, no further tracing will be performed.

 



Example: Secondary Rays Bias

 

This example shows the effect of the Secondary rays bias parameter. The scene below has a box object with a height of 0.0, which the top and bottom of the box occupy exactly the same region in space. Due to this, V-Ray cannot resolve intersections of rays with these surfaces unamibguously.

The first image shows what happens when you try to render the scene with the default settings. You can see the splotches in the GI solution, caused by the fact that rays randomly intersect one or the other surface:

 

 

In the second image below, the Secondary rays bias is set to 0.001, which offsets the start of each ray a little bit along its direction. In effect, this makes V-Ray skip the problematic surface overlaps and render the scene correctly:

 

 

Note that the Secondary rays bias affects only things like GI, reflections, etc. In order to render the scene properly, the material assigned to the box has its 2-sided option checked. This is so that the object looks in the same way regardless of whether the camera rays hit the top or the bottom of the box. If the material did not have this option checked, it would appear "noisy" even though the Secondary rays bias is greater than 0.0: