HDRI Handler

Gaffer has a robust HDRI manager that gives you the ability to quickly switch between your HDR environment maps and adjust brightness, rotation, warmth, etc.

Setup

Before you can use the HDRI handler, you need to tell it where you store your HDRIs.

In User Preferences > Add-ons > Gaffer you will find an option to set your HDRI Folder. Use this to select where your HDRIs are - it will search through all subfolders and find image files with these file extensions: hdr, exr, tiff, tif, jpg, jpeg, png and tga.

If there are multiple variations of each HDRI (such as different resolutions, blurred versions, etc), it will try and group these together so that you have a nice clean list of HDRIs to choose from, and then can optionally choose which resolution etc. to use. This process is not perfect and may require you to manually rename files to ensure they are grouped correctly - see this page for more details.

In the User Preferences it will tell you how many HDRIs were found and let you view a list of them (including how the files were grouped together).

Whenever you add new HDRIs to your HDRI folder while Blender is running, it is recommended that you click the Refresh button in the User Preferences to detect the new files.

First Time usage

All options for the HDRI Handler are in the World settings.

When using the HDRI Handler for the first time, you will be presented with beautiful pink images that say "Thumbnail Missing".

It is recommended that you click the Generate Thumbnails button just below to create the thumbnails for all your HDRIs. This only has to be done once, but it can take a long time if your HDRIs are very high resolution (and you don't have any low-res versions of each one).

The progress bar will give some indication of how long this will take, but may become unresponsive by itself or if you try and interact with Blender. Be patient and wait for it to finish - it is not frozen. You can also follow it's progress by looking at the folder where the images are being saved - on Windows that is C:\Users\you\AppData\Roaming\Blender Foundation\Blender\data\gaffer\thumbs.

Features

Button	Function
Enable	This button (in the panel header) turns on/off the HDRI Handler. When you turn it on, it make a record of your current nodes or World color. When you turn it off, it restores the previous nodes or World color and deactivates the HDRI Handler nodes.
Favorite	Marks the current HDRI as a favorite, to make it easier to find in the future.
Filter Favorites	Filters the list of available HDRIs to just those which have been favorites.
Folder	Filter the HDRI list to only those which are inside a specific folder or sub-folder. Useful if you already organize your HDRIs in the file system.
Search	Type in keywords to filter the HDRI list and find what you're looking for. The name and subfolder (if any) will match your search terms, as well as any tags that you have selected (see below).
HDRI	The main big button for switching between HDRIs
Left/Right arrows	Go to the previous/next HDRI in the list alphabetically. Will loop around to the other side of the list.
Save Settings	Small button at the top left of the HDRI selector - store the current HDRI settings as the default for this HDRI so that you can easily restore them later.
Tags	Small button at the top right of the HDRI selector - use this to add and remove tags to the current HDRI.
Reset	Small button at the bottom left of the HDRI selector - reset all HDRI settings to their defaults. Uses your saved defaults if they exist. Hold shift when clicking it to ignore your saved defaults and use factory defaults instead.
Random	Small button at the bottom right of the HDRI selector - will change to a random HDRI.
Variation/Resolution	If the current HDRI has multiple files associated with it, such as different resolutions or other versions, switch between them here.
Left/Right arrows	Use the next/previous variation/resolution.
Rotation	Rotate the HDRI around the Z-axis. If you need to use the X or Y axis to straighten the HDRI, you need to use the Node Editor.
Brightness	How intense the lighting of the HDRI is. Measured in Exposure Values (EVs), so a value of 1 will double the light, 2 will be quadruple, etc.
Contrast	A direct connection to the brightness/contrast node, making variations in light intensity and color stand out more.
Saturation	0 is black and white, 1 is no change, higher values make colors more colorful.
Warmth	The white-balance of the image - lower values make it more blue, higher values more orange.
Advanced	Toggle the more advanced options below.

Advanced Options

Button	Function
Purple/Green Tint	Adjusts the green/purple color balance to help with white-balance.
Color blending mode	For the Color tint setting (described below), sets the blending mode for how the color is mixed in.
Color tint	The selected color to blend with the HDRI. The Alpha value controls how strongly the color is mixed in using the selected blending mode.
Clamp Brightness	Force the HDRI to be no brighter than this value, while retaining the colors. Use if you want to reduce the intensity of strong lights (e.g. the sun) but retain the intensity of weaker lights (e.g. the sky).
Horizon Shift	Move the horizon of the HDRI down to get any trees/buildings/mountains out of view.
Warp	Squash and stretch factor when using Horizon Shift. Adjust this if the sky looks unnatural after lowering the horizon.
Rotation	Use the value to the right to rotate the background separately from the lighting.
Brightness	Use the value to the right to control the brightness of the background separately from the lighting.
Contrast	Use the value to the right to control the contrast of the background separately from the lighting.
Saturation	Use the value to the right to control the saturation of the background separately from the lighting.
Warmth	Use the value to the right to control the warmth of the background separately from the lighting.
Use for reflections	Use the above (and below) settings for reflections as well as the background/camera.
High-res JPG background	Use a JPG version of the current HDRI to save memory (4x less memory). Requires you to first generate the JPG image, which can take several minutes but only has to be done once. When using this, set the HDRI to a much lower resolution since it will only be used for lighting and (by default) reflections.
Pre-darkened	Use a darkened JPG image (which is brightened up again for the render) so that a sort of high dynamic range is retained and reflections are more accurate. If this is disabled and the (non-darkened) JPG is used for reflections too, they will be dull and not nearly bright enough.