HDRi Skies
HDRi Skies will improve your SketchUp Rendering with realistic backgrounds and exterior illumination.
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HDRI Skies are special 360 degree images of background imagery such as skies, trees, sunsets and buildings that also contain illumination information such as the intensity and color of light based on the background imagery chosen.
What HDRi Skies means to you...
- Accurately illuminate a scene.
- Create realistic reflections.
- Increase realism.
- Featured in IRender nXt and nXtRender.
HDRI (high dynamic range imaging)is a set of techniques that allows a greater dynamic range of exposures (the range of values between light and dark areas) than normal digital imaging techniques. The intention of HDRI is to accurately represent the wide range of intensity levels found in real scenes ranging from direct sunlight to shadows.
HDRi Sky Tutorial
This tutorial shows you how to use the HDRi Sky Lighting default, to add a quick HDRi sky background to a model.
You can easily choose a different HDRi sky, or make other changes after you view a sample rendering.
Using HDRI skies in IRender nXt
We added a new Lighting Preset to IRender nXt - HDRi Sky
Because of the new Image Layer Wizard, which makes it easy to rotate and position HDRi skies, more and more people are using HDRi skies in their models.
This new Lighting Preset automatically makes the best settings for HDRi skies, and selects a nice sky with a mountain, background trees, sky and clouds.
If you want to use a different HDRi sky, choose this preset and then go to the HDRi Setup tab to choose a different sky.
IRender contains several HDRi skies from various sources, including ArchVision, AccuStudio and EverMotion. You can click on the plus sign to cycle between the included HDRi skies.
If you want to make HDRi Skies visible, or just reflective, use the Sun/Sky Tab to adjust the settings
In order to see the HDRi skies, you need to turn the sky on, and select an HDRi sky. None of the 4 lighting defaults selects HDRi sky and makes the sky visible, so you need to do this manually on the Sun/Sky tab. In the example on the right, we selected the Exterior Default, then turned off the sun, and turned on HDRi sky mode (we selected the HDRi sky to use from the HDRi tab).
Resolution Issues
HDRi skies don't work well for backgrounds unless you have a very high resolution HDRi, or use a very large Field of View.
If you use a standard FOV of 35, then you're only using 10% of the width of the HDRi image and stretching part of the image across the background of your rendering (35 degrees is about 10% of 360 degrees).
So, for a 1000 pixel rendering, you would need a 10,000 pixel HDRi image for a 35 degree FOV to render at highest quality.
If the FOV is small it will look like you are zoomed in on the background image, the wrong scale. It's better to use a larger FOV for exterior scenes for which you want to use an HDRi sky for the background.
If you set the FOV to 90, then you will see 1/4 of the HDRi image as a background. That kind of works, but of course you may get distortion from the 90 FOV in the perspective view. 2 Pt Perspective may help with this.
Here I used StJohns_09_2.hdr, one of the highest resolution HDRi files that are included with the libraries. It has a width of 4096 pixels. And I used a FOV of 90 and turned on 2 pt perspective.
So it's using about 1/4 of the entire HDRi image: (This is hard to see here because this is a flat representation of a Panoramic HDRi Image)
Here is another sample with a 90 degree FOV for an exterior - without 2 PT Perspective.
(Using the Bear Mountain HDRi from our library)
Working with Shadows
You can turn on the Sun with HDRi skies to get harsher shadows.
Note:There is currently no easy to align the SketchUp Sun to the sun in the HDRi image
When both HDRi skies and the sun are used for illumination you may need to balance the illumination from the sun and the HDRi sky using lighting shadows.
HDRi Sky with no sun
This image is a beach cottage illuminated by only the HDRi Sky Preset.
The sun is off and there are only subtle shadows.
HDRi Sky with Sun
Here I turned on the sun to get a distinct shadow, but it made the HDRi sky too dark.
Balanced with Lighting Channels
I used Lighting Channels to lower the intensity of the sun from 1.0 to 0.1
This gave me the brighter sky which I wantred.
Using a Background Image instead of an HDRi Sky
For this image, I turned on the sun, and used a background image instead of an HDRi sky.
See also
Sources
Free HDRI Skies:
- HDRI Haven - A great site to get free HDRI images.
- HDRI-Hub.com - HDRI-Hub.com is your first address for royalty free, high resolution 360-degree High Dynamic Range panoramas and high quality architectural textures. These enable you to light and shade your 3D scenes photo realistically. You will find the panorama images and textures in our shop.
- OPENFOOTAGE.NET - 35 Full 360 degree HDRI Panoramas for backgrounds
- www.accustudio.com AccuStudio Gallery - go to Exchange and then HDRI.
- EverMotion
- Brian Jame's HDRI collections
- Paul Debevec Probes
- Max Planck Institut OpenEXR
- USC - ICT Graphics Laboratory
- Keith Bruns HDRI Gallery
- Evermotion.org
- Greg Ward, Anywhere Software
Not free HDRI files: