Introduction

The goal of SceneSkies is to give you beautiful and realistic lighting and background environments for your 3d scenes, in the fastest and most convenient way.

What is SceneSkies?

SceneSkies is made of two parts:

  1. several collections of HDR images for lighting and surrounding your scene. These can be used in any software that supports equirectangular EXR images. They are available at different resolutions and prices.
  2. an optional and free Blender addon that makes it easy to use them in Blender.

SceneSkies’ HDRs have several advantages over most other collections, they:

  • depict scenes never seen before, such as on Mars or above the clouds. Some skies have a ground (mountains etc), and some do not, like on a gaseous planet

  • don’t have clutter in the foreground, such as plants or other objects, perfect for far away backgrounds around your 3d scene. They are made specifically for large-scale scenes and to be used as a horizon

  • show the same scenes at different times of the day (including night time) and different weather conditions

  • give sharp shadows in clear weather conditions

  • have a very high range of brightness:

    • are never burnt out in very bright areas, for instance the glow in the atmosphere around the sun, or sun reflections on water bodies
    • are never totally black in very dark ones, such as direct shadows at noon, or at night time
  • can be customized to some extent: it is possible to change the color and intensity of different elements of the image, independently: the sun, the atmosphere, the clouds, the ground

  • are available in several resolutions, up to 16k

Note

When using color-tweaking several maps have to be combined together, to form the final composited HDR panorama image. All these maps are at the chosen resolution, and use RAM. For high resolutions, this can add up very quickly. So make sure you have enough RAM. The recommended minimum system RAM is 16GB for 16K (7GB will be used), and 8GB for 12K (4GB will be used). When color-tweaking is disabled, only about 1GB of RAM is needed at 16K.

SceneSkies’ Blender addon has the following features:

  • allows you to quickly see all your installed HDRI collections, list the HDRIs as thumbnails, and select the one to use in the current scene
  • use your own HDRIs. Note that to support color-tweaking the HDRIs need a specific preparation. See here
  • lets you rotate the environment to change the direction of the sun light
  • lets you control the color and intensity of the sun, clouds, atmosphere and ground

What is HDRI-based lighting

HDRI stands for High Dynamic Range Image (or Imaging), it means an image where each pixel has color values that are beyond the usual 8-bit integer precision per channel of the common image formats. For example JPG images, used to save photos or web images, have 8 bits to code values for each color channel (red, green and blue). In 8 bits, it is possible to encode only 256 values. On the other hand, HDR images used in SceneSkies are EXR images, and have 16 bits per channel. That means they can encode thousands of floating-point values (hence “High Range”), for each color.

The direct benefit is that colors are no longer totally black (value = zero) in shadows, or totally white (max value) in direct light, but instead keep their very low or very high color information, and can be revealed (or hidden) to our eye by adjusting the intensity of the image (hence “Dynamic Range”), depending on our needs. Black, at pixel value zero, will remain black, no matter how brighter we make the image. However a very low pixel color value, such as 0.1 for instance, can be multiplied and scaled, and become brighter. Like in real life, there’s light everywhere, including in very dark places. It’s just that our eye (or cameras) can’t see.

HDRIs also show a complete 360° panorama. They often look distorted when opening them in an image editor, but that’s because they are mapped onto a sphere, for those in equirectangular projection. That sphere surrounds your whole 3d scene, giving a background without the need to have actual geometry.

The renderer uses the whole image to light your 3d scene. Each pixel color is used as a light source, and since they have a very high range of values, it is possible to have very bright areas, such as the sun. With this technique the 3d scene seems to be part of the surrounding environment, even though it is just an image, and not an actual 3d environment. It is very close to what happens in real life, where each surface receives light from all around it, including bounced light from the ground for instance, not just direct sunlight. This rendering technique produces highly realistic lighting easily. No need to manually tweak lamps.

To recap, HDRIs serve two purposes:

  • giving a whole 360° background around your 3d scene
  • providing realistic lighting

while having very wide color intensities. HDRIs have no drawbacks, so who wouldn’t use them ;) This is a general presentation. More information is readily available on the web if you are interesed to learn more about it.