GI for Exterior and Interior Scenes

Introduction

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In this chapter we'll cover some good settings of V-Ray that work for rendering exterior and interior scenes. You can check the original design-oriented tutorials here and here, and get the assets from them.

Exterior

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The common setup for exterior scenes is Brute Force for primary engine with Brute Force or Light Cache for secondary.

Check the GI_Exterior.vrscene file from the scene bundle. Try out the different sets of #includes for different GI settings for exterior scenes.

Interior

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The choice of GI engines and their parameters is paramount, especially for interiors where most of the illumination is indirect. Bad choices can lead to too much noise or artifacts and/or disproportionate render time for certain image quality. The common setup for exterior scenes is Irradiance Map for primary engine with Light Cache for secondary.

Check the GI_Interior.vrscene file from the scene bundle. Try out the different sets of #includes for different GI settings for interior scenes.

Preview

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The common setup for fast previews is Light Cache both for primary and secondary engine.

Parameters

We can tweak the SettingsRTEngine.gi_depth. It controls the maximum depth for tracing diffuse GI rays and defaults to 3. Lower if you need faster rendering and the scene is exterior. For interiors you may need to increase to get enough lighting, otherwise the scene may remain too dark.

We can also play with SettingsRTEngine.coherent_tracing. It controls experimental grouping of rays for coherency (disabled by default). This can improve performance on GPUs because they handle non-divergent code better. The first few sampling passes will have lots of artifacts, because entire groups of rays move together. Over time this should disappear and the final result should converge to the same image as when this is turned off. This option is only useful for interiors with lots of GI on GPU.

Examples

Exterior

Here we see the direct and indirect lighting broken out to help see what areas are contributing to the final result:

Here's the final result:

Interior

Here again we see the direct and indirect lighting separately:

Here we see render times of different combinations of GI engines: