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hdri.md

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HDRI

Usage

  • Activate Use nodes for the world shading.
  • Add an environment texture node, and load the .hdr file in there.
  • It can be worth keeping the background node in order to remain able to manage the strength of the lighting. Plug the environment texture to it.
  • If rotation is necessary:
    • plug in a Mapping node connected to Generated Texture coordinates into the vector input of the environment texture. Ctrl + t with Node Wrangler addon enabled.
    • set suitable rotation

Creation

Resources:

Night sky star map using NASA data

NASA provides a map of the sky in this page: Deep star maps.

Credit:

NASA/Goddard Space Flight Center Scientific Visualization Studio. Constellation figures based on those developed for the IAU by Alan MacRobert of Sky and Telescope magazine (Roger Sinnott and Rick Fienberg).

How to use as HDRI:

  • Download celestial coordinates version of the star map (tif file).

  • Convert to hdri format using command convert (linux / imageMagick):

    convert starmap_16k.tif starmap_16k.hdr

  • Profit!

For the higher resolution versions of the sky map, imageMagick might throw the following error:

convert-im6.q16: width or height exceeds limit `starmap_16k.tif' @ error/cache.c/OpenPixelCache/3912.
convert-im6.q16: no images defined `starmap_16k.hdr' @ error/convert.c/ConvertImageCommand/3258.

In such case, limits should be increased in the policy.xml config file (source with details).

Both height and memory limits might need to be increased. Adapt setup according to machine's power.

Location in debian buster: /etc/ImageMagick-6/policy.xml

  <policy domain="resource" name="temporary-path" value="/home/tmp"/>
  <policy domain="resource" name="memory" value="2GiB"/>
  <policy domain="resource" name="map" value="2GiB"/>
  <policy domain="resource" name="width" value="50KP"/>
  <policy domain="resource" name="height" value="50KP"/>
  <!-- <policy domain="resource" name="list-length" value="128"/> -->
  <policy domain="resource" name="area" value="1GiB"/>
  <policy domain="resource" name="disk" value="3GiB"/>

N.B. Using the .tif file directly as environment texture works in blender, but the brightness is way better in hdri format.