Why do they use HDR images for Skyboxes?

[ViaCognita]

Hi!

I’ve been watching some videos about how to create a skybox, and all of them use HDR images.

What is so special about these images that they are used in skyboxes?

Thanks!

[ClockworkOcean]

I think it’s two things

1. They are High Definition ( dynamic range ), as the name says

2. They provide accurate lighting in the scene. It’s not just a pretty background

[ViaCognita]

@ClockworkOcean The image than I want to use is in Open EXR format. Do I need to convert it to HDR? Or, does it have enough quality to use it in that format?

I’ve been reading this article Using HDRI in Unreal Engine: A Step-by-Step Guide, and the writer said in the 1. Importing the HDRI Image section:

In the Import window, make sure the Format is set to EXR (HDR 32-bit).

Thank you.

[3dRaven]

@ClockworkOcean

They are High Definition, as the name says

HDR => High Dynamic Range => in other words it has multiple levels of exposure sandwiched inside of the image, so an image with low lighting range (under exposed) up to an image that is overexposed. This allows for the image to exceed the normal range of 0 - 255 color range that is used in simple images.

It has more data internally about the lighting condition than a normal image hence it is used for skyboxes as you can manipulate the intensity of the light at a more detailed level.

[ViaCognita]

@3dRaven The image than I want to use is in Open EXR format. Do I need to convert it to HDR? Or, does it have enough quality to use it in that format?

Thanks!

[ClockworkOcean]

I never could import EXR, so quite quite possibly, yes…

[ViaCognita]

@ClockworkOcean The images I want to use are here: NASA SVS | Deep Star Maps 2020

I just drag and dropped inside Unreal Editor. I’m using version 5.4.4.

[3dRaven]

@ViaCognita

Open EXR

Tutorial – How to use OpenEXR (.exr) material textures in Unreal Engine 4.25...

Seems they should be converted from a disk space standpoint (they are too heavy to leave as EXR files)

[EvanHammel (PixelDriven)]

If you want to input the HDR file into an HDRIBackdrop actor, you will need to convert it to a .HDR file first. This is a limitation of the HDRI backdrop plugin. You can do this in Photoshop, Affinity Photo, etc, and then import it to Unreal.

If you are using the HDRI in a material instead, you just need to make sure the Texture Sample node is set to Linear Color for the sampler type, and it should accept either an EXR or HDR file.