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For a proper IBL workflow, three aspects are key to achieve eye-pleasing imagery:
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Unlike other renderers (that generally fail at sampling IBL environments efficiently), 3Delight provides a proprietary, state of the art, environment sampling algorithm which does not require users to rely on caveats like:
- using multiple versions of the HDRI for different ray types;
- downsizing the HDRI;
- blurring the HDRI;
- manually controlling the multiple importance sampling of the HDRI, e.g. by setting a "sampling resolution" number.
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- An image captured on set by taking multiple photographic exposures and post-processed them into a single image.
- A procedural sky texture (the Hosek & Wiklie model, used in the 3Delight Sky, provides superior quality than the Preetham model).
- A manually crafted image, wether hand painted or created with ad-hoc authoring tools such as "HDRI Light Studio".
- A pre-rendered image (HDR, EXR) in lat-long format, you can use the spherical camera projection to render a HDR rendering of your 3D set and then re-use it as environment in situation where the full 3D set is not required.
What mapping should I use?
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- Interiors without any openings towards the exterior (e.g. a fully enclosed room with no without any openings, such as windows and doors, allowing external light to come in).
- Interiors with openings (e.g. a room with windows, doors, or oher other type of openings).
1. Room without openings
- Create (geo) Area ) Lights, matching size and position, for each light sources that illuminates the scene (typically large area lights, neons etc.)
- Make sure all Lights have inverse square falloff (required by physics for plausible lighting)
- Assign to emissive objects (such as neons) a fully incandescent shader with incandescence value near or equal to 1 (this will change in the future and overbought intensity , for now incandescence levels near to 1 won't cause additional noise).
- OPTIONAL: Create an HDRI environment with a texture that loosely matching the interior you are rendering. If you have a texture acquired on set for VFX this is the best case scenario. If teh set is full 3D you can render a spherical projection version of your environment.
- Turn on Indirect Illumination
- Set Indirect Illumination Diffuse Bounces to 3 or more (increase by 1 unit as the effect might become neglectable after many bounces, looking at statistics will help).
- Set the Indirect Illumination> Max Distance to force environment rays to be called inside the interior: e.g if your room would fit in a sphere of radius 50 units, set the max distance to 25 (or less) units.
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Note that 3Delight has no problem using a higher number of diffuse bounces. Typically fully enclosed interiors will require around 4 to 6 bounces .(check statistics for precise feedback) |
2. Room with openings
- Setup HDR Environment
- Push Set indirect diffuse bounces to higher values, up to 16 bounces are possible, with tiny impact on performance.
Optionally:
- Position Area Lights behind light entry areas (typically windows) and setup an HDRI environment
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- 3 or more (check statistics for feedback)
- Positioning Area Lights behind openings (typically dorrs / windows) towards the exterior will help "pushing light" inside the roomPosition Area Lights behind light entry areas (typically windows), but this time declare them as "portals" to focus an outside HDRI environment you have setup