Indirect illumination section
Search Keywords: switches, global switches
The global switches allow you to control various aspects of the renderer globally.
Displacement - enables (default) or disables V-Ray's own displacement mapping. Note that this has no effect on standard Max displacement mapping, which can be controlled via the corresponding parameter in the Render Scene dialog.
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) will appear fully transparent. This allows to look inside closed objects when the camera is outside.
Lights - enables or disables lights globally. Note that if you uncheck this, V-Ray will use the default lights. If you do not want any direct lighting in your scene, you must uncheck both this and the Default lights parameters.
Default lights - allows you to control the default lights in the scene.
Off - the default lights in the scene will be always switched off
On - the default lights are always switched on when there are no lights in the scene or when you have disabled lighting globally (see Light parameter).
Off with GI - the default lights will be switched off only when the Global Illumination is enabled or if there are lights in the scene
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) will not be 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.
Probabilistic lights - this option enables optimized sampling for scenes with many lights. When this option is disabled, for each hit point, V-Ray goes though each scene light and evaluates it. In scenes with many lights and lots of GI bounces, this leads to a lot of shadow rays being traced, to the point that the whole rendering becomes extremely slow. When this option is enabled, V-Ray will choose randomly the specified number of lights and will evaluate only those. Lower values will make the rendering faster, but potentially more noisy. Higher values will cause more lights to be computed at each hit point, thus producing less noise, but increasing the render times.
This option introduces some additional noise but it makes it possible to render images that would otherwise take a very long time.
When loading scenes saved with V-Ray 2.x, the option is turned off in order to produce the same result.
Below is an example rendering of a scene with 1089 sphere lights with their Cutoff threshold set to 0.0. Both images were rendered with the Progressive image sampler and ran for the same amount of time. When probabilistic lights are enabled, the image is much cleaner as V-Ray manages to compute more GI rays (which are the main source of noise in this scene).
Probabilistic lights is off Probabilistic lights is on (8 lights)
Reflection/refraction - enables or disables the calculation of reflections and refractions in V-Ray maps and materials.
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.
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 GI - 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. transp levels - this controls to what depth transparent objects will be traced.
Transp. cutoff - this 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.
Override mtl - this option 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.
Override exclude - clicking this button brings up the 3ds Max Include/Exclude dialog which allows you to select exactly for which objects the material is overridden.
Glossy effects - this option allows the user to replace all glossy reflections in the scene with non-glossy ones; useful for test renderings.
Indirect illumination section
Don't render final image - when this option is on, V-Ray will only calculate the relevant global illumination maps (photon maps, light maps, irradiance maps). This is a useful option if you are calculating maps for a fly-through animation.
Max ray intensity - this option allows to supress 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 loosing 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.
This parameter is turned off when loading scenes saved with V-Ray 2.x in order to produce the same results.
Secondary rays bias - a small positive offset that will be 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. See the Examples section for a demonstration of the effect of this parameter. This parameter is also useful when using the 3ds Max Render-to-texture feature.
Legacy sun/sky/camera models - previous versions of V-Ray used slightly different calculation models for the VRaySun, VRaySky and VRayPhysicalCamera which were not entirely physically accurate. When this option is off (the default), V-Ray uses improved and more accurate models. When this is on, V-Ray will switch to the old models for compatibility with old scenes. When an old scene is opened, V-Ray will automatically display a dialog asking if you want to change this setting.
Use 3ds Max photometric scale - when on (the default), this option aligns the VRayLight, VRaySun, VRaySky and VRayPhysicalCamera to the photometric units used by 3ds Max and its photometric lights. When this is off, these plugins operate in the internal V-Ray photometric space, like in older versions of V-Ray. Keeping this option on ensures that a VRayLight with a given power will match a 3ds Max photometric light with the same power.