HDRI in Lightwave
by Matt Lester and Jay Weston



This tutorial has been written to serve Hyperfocal Design's customers who are using their HDRI sky textures, but can be just as easily used for other HDRI environments. This tutorial attempts to cover every aspect of HDR rendering in Lightwave 8, but since radiosity and HDR support hasn't changed much since 6.5, users of older versions should be fine. Provided that your HDRIs are of good quality, you should have a great end result for your background, lighting and reflections using HDRI after completing this tutorial.

This tutorial is not aimed at the novice, it will not explain how to perform very basic operations in Lightwave, please consult your manual if you need help with these basics. LW8 supports HDRI out of the box, no plugins are required.


HDRI Artifacts - Splotches, Speckles, Tiny Dots

Before we begin the tutorial and cover all of the HDR controls in LW8, we must address a very common problem that exists in some 3d software packages that support radiosity and HDRI. This problem is usually called "splotchiness" or "speckles", and it can be caused by either radiosity settings which are too low to create smoothing lighting and shadows, or the use of HDRI maps which contain small but bright regions, such as windows or the sun.

Each software package has its own method of fixing this problem, as detailed below.


A large percentage of Hyperfocal's HDR skies are photographed with the sun just behind or fully covered by clouds, increasing the size of the light source and giving the artist the option of creating either a soft or hard shadowed look.

HDRI in Lightwave

Image Editor

Image Editor (F6) -> Load your HDR in .hdr format -> set gamma to 2.2 in the editing tab.Most HDR images are created at gamma 2.2 so failing to do this will result in very poor renders with loads of splotches/speckling artifacts.


Gamma 1

Gamma 2.2

Adjust Brightness
Adjusting brightness will affect the brightness of the hdr itself as well as the lighting of the scene.

Contrast

Will adjust the contrast of the hdr and the lighting, but introduces splotching/speckle artifacts.

Hue & Saturation
Adjust to suit your scene/taste

Filters

If you are having trouble with speckle/splotching artifacts, apply a full precision blur filter to your lighting hdr (see the two hdri method)



HDRI Environment Map

You can set up your scene in one of two ways.

One HDRI: Use one HDRI for both your background image and for your lighting, either mapping to a 3d inverted sphere or as a lightprobe environment.

Two HDRI's:
Use one HDRI mapped to an inverted background sphere which will be visible in the render, but will not provide lighting. Then use another HDRI mapped to another inverted sphere which will provide lighting to the scene but will not be visible in the render.



One HDRI: Inverted 3D Sphere Method
Load a sphere object with inverted normals and apply the hdr as a spherical map.

Inverted Sphere


Luminosity 100%
Diffuse 0%
Seen by Camera: ON
Seen by Rays: ON (when using only one HDRI, we need the bg image to also provide lighting)
All shadows options: OFF
Exclude all lights from lighting this object


For the sphere, you will need to make it large enough so that it appears to be in the distance, however the larger (further away) the sphere is, the more innacurate the lighting and shadows become. See the GI/Interpolated section to set this up correctly.

Once your HDR image is mapped, you can edit the properties to align/rotate the environment/sky as you wish.

Select Lights (Shift L) -> properties

Clear all lights - all lighting will be provided by the HDRI

Set light intensity to 0



One HDRI: Light Probe Environment Method


A big drawback to this method is that you can't view your hdr in the viewport in realtime, you have to do test renders to find out where the sun is. This makes adding a direct light over the sun extra difficult as well (see adding traditional lights for hard edged shadows) So this method isn't recommended.

Convert the lat/longitude spherical format to lightprobe format in a program such as HDRShop.

Open the effects window (^F5) -> add Environment -> Image World -> edit properties -> select light probe image



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