uring the past few years High Dynamic Range Imaging (HDRI) has become a popular approach for creating a realistic lighting setup and dynamic reflections in 3D computer graphics. A proper HDRI environment saves you the time of carefully placing and adjusting traditional CG lights in a 3D scene by offering a prefabricated lighting / reflection setup processed into a bitmap that can be wrapped around a scene. A photographic HDRI environment bitmap is usually photographed using special equipment that captures a 360 degrees panoramic environment. The capturing process is executed in multiple passes (f-stops), gathering a wide range of dynamic color / light intensity data of the environment. It's this high range of image information that makes the result suitable for a 3D environment that's dynamic enough to properly light a scene and provide robust reflections and refractions.

HDRI environment lighting used to create a convincing virtual lighting and reflection setup.

HDRI-STUDIO
At the time of writing this review there is still a limited number of commercial HDRI environment collections available. The majority of those collections comprises HDR photographs of common outdoor and indoor surroundings, providing a suitable environment for purposes such as architectural visualisation. The HDRI-Studio initiative (www.hdri-studio.com) distinguishes itself from the conventional HDRI collections in two ways. First of all HDRI-Studio delivers softbox lighting setups for virtual studio photography in stead of scenery like landscapes and architecture. The second difference is that the HDR images can be ordered individually, using a convenient online database. A fine example of this convenience is a special preview window option accompanying each individual HDRI. The preview window contains an interface that enables you to interactively view twelve different renders of a 3D scene, displaying incremental angles of the environment lighting / reflection.

HDRI-Studio's interactive online HDRI effect viewer.

DYNAMISM
With the increasing availability of HDR imagery it is important to be aware of the differing quality of HDRIs. Of course there are the obvious visible quality flaws, such as uninteresting imagery and/or visible compression artifacts of JPG photographs combined into a HDR image. But there is also an important hidden quality factor: the actual extent of the dynamic range. The dynamism of a HDR image is determined by the number of f-stops it includes. The more f-stops used for a HDR image, the more detailed color / light intensity data it contains. More f-stops result in a richer color / light quality, causing more pronounced shadows and shading contrast.

Luckily HDRI-Studio lives up to the highest current standard of HDRI dynamism. Each image is captured using a single 360° pass with the equivalent of 26 f-stops of bracketing. That is the highest possible dynamic range at this moment, and it shows. Below you can see a birth-card illustration I created in 3ds Max for a client. I rendered it with the plug-in rendering suite VRay, using a HDRI-Studio image in the scene's environment as the only lighting. As you can see the differently colored softbox lights in the HDRI provide a varied lighting and reflection result, with nice, tinted soft shadows being cast from the objects in the scene, while the HDRI intensity is not even at full strength and the renderer's settings are not optimal.

The HDRI-Studio HDR images have the correct spherical distortion to be properly used in a panoramic spherical environment and they come in three shapes: "Neutral", "Gels" and "Abstract". The categories will soon be supplemented with "Automotive", customly designed for attractive automobile visualisations.

The Neutral HDRIs provide a balanced monotone lighting, the Gels are there to add some moody color variation to your lighting and the Abstract ones are useful for graphic effects in your lighting and reflections. Each HDRI is available in the widely supported .hdr format and you can select several different resolutions for different applications, ranging from large-scale environment lighting to detailed close-ups. Obviously higher resolutions mean a higher price, but the choice for the right resolution is up to you and your specific needs. Options for single-user and multiple-user licenses as well as value bundles are available and ordering is easy: select your desired HDRI, then choose the resolution you need and place your order. When the transaction is completed you will be able to download your purchased HDR image.

HDRI-Studio offers the highest HDRI quality for an affordable price. Whether you're a 3D pro or a motivated 3D hobbyist, be sure to check out HDRI-Studio.com for a useful addition to your creative arsenal.

Metin Seven

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