Image Based Lighting (IBL)

WIP - PLESE DO NOT EDIT: UNDER WRITING!!!

Image-Based Lighting (IBL) is a CG technique/workflow to light a 3D scene via the sole use of and High Dynamic Range Imagery (HDRI) usually under a form of a file pre-processed texture or a procedural generated texture (e.g. a sky) which encompass the whole scene.

Unlike other renderers which do not exploit MIS or exploit MIS in non optimal ways. 3delight provides a state of the art algorithm which does not require users to:

• downsize the HDRI
• blur the HDRI
• use multiple versions of the HDRI input for different ray types
• manually control the multiple importanc esampling of the the HDRI by setting a sampling number

In 3Delight we encourage you to:

• as a rule of thumb use always twice your render output resolution as the resolution of your HDRI, e.g. if you are rendering a full HD frame 1920*1080, then your ideal HDRI resolution is 3840x2160.
• never force to blur your HDRI: simply dont worry 3delight knows what to so and will use the aame etxture for diffuse and specular lighting in the proper way.

Lighting:

- illumination

- shadowing

- reflections/refraction

- background

- athmospherics

Imagery:

- an image acquired on set by taking multiple photographic exposures and postprocessed into a single image

- a procedural sky texture (usually using the Hosek & Wiklie model)

- a crafted image, wither hand painted or created with tools such as "HDRI Light Studio"

Mapping:

- latitude/longitude

- spherical image

Step-by-step guide

Setting up IBL is very simple in 3Delight:

1. create the IBL node and map a hdri image or a procedural sky
2. enable indirect illumination

Here detailed step that take into account the pre-requisites:

1. create/import some geometry
2. apply the all around 3delight “phisically/visually plausible” material: 3delightMaterial, make one object diffusive, one reflective and one refractive
3. in the preference choose to render on maya render view to see the result in the MRW or in  i-display so to see all the image layers in one go
4. select 3delight as a renderer
5. renderglobals: in the common section enable linear workflow
6. renderpass: create a delight environment
7. apply a texture or a procedural
8. render, you will get mostly a black image except if on the 3Delight material you have set some reflectivity or refractivity which will be stored in the relative image layer
   
   If you do not enable indirect illumination you will not use the environment to illuminate your scene (indirect diffuse) nor receive any information from the surface-to-surface color transport. unlike relfecttion and refraction which are indirect specular effects, in order to receive indirect diffuse and colro bleed in you must turn on indirect illumination.
    
9. renderpass: enable indirect illumination
10. render again, now  your main buffer feature also the indirect diffuse and environment diffuse, additionally all  AOVs are filled accordingly
11. optionally you can put the environment image in the background: this is for previews only, ideally the envronemnt should be composited in your compositor app of choice.

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