Light Probe Image Gallery

Updated 10/9/04

SIGGRAPH Course

Paul Debevec, Dan Lemmon, and colleagues taught a half-day course on Image-Based Lighting at SIGGRAPH 2001 and 2003. The web page (with the final notes) for the course is here. The course covered both the theory and practice of using light probe images to illuminate computer-generated objects. At this course we announced the release of HDR Shop, a tool for processing and manipulating high-dynamic range images including light probes.

Introduction

A light probe image is an omnidirectional, high dynamic range image that records the incident illumination conditions at a particular point in space. Such images were used in the paper Rendering Synthetic Objects into Real Scenes: Bridging Traditional and Image-Based Graphics with Global Illumination and High Dynamic Range Photography at SIGGRAPH 98 to illuminate synthetic objects with measurements of real light, and later in a SIGGRAPH 2000 paper to illuminate real-world people and objects. Two of our animations, Rendering with Natural Light and Fiat Lux demonstrated the use of image-based lighting. The commercial product LightWave 3D v6 was the first to support image-based lighting in 1999 and the technique is now commonly supported; see below for links to some sample renderings made using our probe images. Some of these images were assembled from high-dynamic-range panoramas, others were acquired by taking one or two high dynamic range images of a mirrored ball (see Reflection Mapping).

RADIANCE Image Format and Viewing on Unix

Light Probe images are measurements of light in the real world, and thus are high dyanmic range, with pixel values ranging from thousandths to hundreds of thousands. Because of this, these images are provided in the RADIANCE Synthetic Imaging System .hdr image format (Described in Greg Ward's "Real Pixels" article in Graphics Gems II.) They can be viewed on an X11 display using RADIANCE's ximage program and/or converted to floating point data using the "pvalue -df -H -h" program from the RADIANCE package. RADIANCE images also use the more traditional but somewhat ambiguous .pic filename extension, so feel free to rename any of the .hdr images to .pic if your software requires this.

Viewing and Editing HDR Images

The images may also be viewed using USC ICT's program HDR Shop.

Raw Floating-Point Image Data

The raw floating-point format images are 4-byte single precision, big-endian, with interleaved color planes. There is now also a directory with little-endian versions of these float images (which are useful if you're using a PC rather than an SGI, for example). Take note of the image dimensions so that you can load them correctly. We have also developed a very simple floating-point version of the Portable Pixmap .ppm format (.pfm for Portable Floatmap) which we will support shortly, along with the floating-point versions of the TIFF format.

Making Your Own Light Probes

If you're interested in creating your own high dynamic range images, the HDRShop package developed at the USC Institute for Creative Technologies is now available. One of the easiest ways to create a light probe image is to acquire a high dynamic range image of a mirrored ball; other techniques involve stitching multiple images together (such as with Panorama Tools or RealViz's Stitcher), or using a scanning panoramic camera such as the ones available from Panoscan or Spheron.

Light Probe Images

The following light probe images were created by taking two pictures of a mirrored ball ninety degrees apart and assembling the two radiance maps into full sphere. The coordinate mapping of these images is such that the center of the image is straight forward, the circumference of the image is straight backwards, and the horizontal line through the center linearly maps azimuthal angle to pixel coordinate.

Thus, if we consider the images to be normalized to have coordinates u=[-1,1], v=[-1,1], we have theta=atan2(v,u), phi=pi*sqrt(u*u+v*v). The unit vector pointing in the corresponding direction is obtained by rotating (0,0,-1) by phi degrees around the y (up) axis and then theta degrees around the -z (forward) axis. If for a direction vector in the world (Dx, Dy, Dz), the corresponding (u,v) coordinate in the light probe image is (Dx*r,Dy*r) where r=(1/pi)*acos(Dz)/sqrt(Dx^2 + Dy^2).

Note that each light probe image represents a full 360 × 360 degrees, or 4pi steradians. Also note that the mapping being used is different than the mapping one observes in a mirrored ball -- the mapping we use avoids the problems of poor sampling near the backwards-facing directions around the circumference of the image. These images have also been converted (using HDR Shop) to the vertical cross environment cube format and are available in this format below.

Note on downloading:

The light probes need to be transferred as binary files. However, since the .hdr format beings with a text header some browsers. To avoid this problem, all of the probes are available as one gzipped tar file all_probes.tar.gz; it's 18,557,917 bytes. If you're using a PC rather than a Unix-based machine, you can download all of the images as a zip file all_probes.zip which is 20,686,564 bytes (some PC programs don't untar Unix files correctly).

Grace Cathedral, San Francisco
1000 × 1000
Dynamic range: 200,000:1

Angular map: .hdr | .exr | .float.gz | .pfm
Latitude-Longitude: .hdr | .exr

Used as the illumination environment for Figure 6 of the SIGGRAPH 98 paper. Assembled from two radiance images of a mirrored sphere taken with a Sony VX1000 digital video camera (approx. ten image per sample.)

Eucalyptus Grove, UC Berkeley
900 × 900
Dynamic range: 5000:1

Angular map: .hdr | .exr | .float.gz | .pfm
Latitude-Longitude: .hdr | .exr

Used as the illumination environment for Rendering with Natural Light; acquired similarly to the Grace Cathedral image.

St. Peter's Basilica, Rome
1500 × 1500
Dynamic range: 200,000:1

Angular map: .hdr | .exr | .float.gz | .pfm
Latitude-Longitude: .hdr | .exr

Used as some of the illumination data for the main sequences of Fiat Lux. Assembled from two radiance images of a mirrored ball and then touched up at the bottom using Photoshop. Each Radiance image was assembled from six exposures, three stops apart, from a Kodak DCS520 digital camera.

The Uffizi Gallery, Florence
1500 × 1500
Dynamic range: 500:1

Angular map: .hdr | .exr | .float.gz | .pfm
Latitude-Longitude: .hdr | .exr

Used as the illumination environment for the middle sequence of Fiat Lux. Assembled from a set of eighteen images forming a full-view panorama; it has the greatest detail of any of the images on this site. Newly discovered video shows the Uffizi Gallery Light Probe being taken in Feb. 1999 in Florence.

Galileo's Tomb, Santa Croce, Florence
1000 × 1000
Dynamic range: 7000:1

Angular map: .hdr | .exr | .float.gz | .pfm
Latitude-Longitude: .hdr | .exr

Used as the illumination environment for the final sequence of Fiat Lux, taken similarly to the St. Peter's probe but not retouched.

Skull lit with this image in LW3D
by Terrence Walker

Single Image Light Probes

The following light probe images were created from single high dynamic range images of a mirrored ball. Since just a single image was used, the images show the camera and the photographer and they are not well sampled in the area that is opposite the camera.

Kitchen at 2213 Vine St
640 × 640
Dynamic range: 2000:1

Angular map: .hdr | .exr | .float.gz | .pfm
Latitude-Longitude: .hdr | .exr

Used as the illumination environment for Figures 2, 3, 4(a), 5, and 8 of the SIGGRAPH 98 paper.

Overcast Breezeway, Soda Hall
640 × 640
Dynamic range: 1000:1

Angular map: .hdr | .exr | .float.gz | .pfm
Latitude-Longitude: .hdr | .exr

Used as the illumination environment for Figure 4(b) of the SIGGRAPH 98 paper.

Campus at Sunset
640 × 640
Dynamic range: 2000:1

Angular map: .hdr | .exr | .float.gz | .pfm
Latitude-Longitude: .hdr | .exr

Funston Beach at Sunset
640 × 640
Dynamic range: 800:1

Angular map: .hdr | .exr | .float.gz | .pfm
Latitude-Longitude: .hdr | .exr

Skull lit with this image in LW3D
by Terrence Walker

Probes in the Vertical Cross Cube Format

The following images are the above nine light probes converted to the vertical cross cube format using HDR Shop. They are available as RADIANCE .hdr images or low-dynamic range 8-bit TIF images.

RADIANCE .hdr:

Portable FloatMap .pfm:

Low-dynamic Range TIF:

More Images

There are some additional high dynamic range images on the main high dynamic range images page.

Illuminating Synthetic Objects with Real Light

Using RADIANCE

Check out the source files for our animation Rendering with Natural Light, which demonstrates image-based lighting in RADIANCE.

Using IBL in LightWave 3D 6 and up...

Image-Based Lighting has been implemented in NewTek's LightWave 3D package, and the Light Probe Image Gallery has been included on their distribution CD. Some sample images of skulls rendered using the probe images have been rendered in LW3D by Terrence Walker.

Marko Dabrovic has prepared a tutorial on rendering virtual Light Probe images from Terragen and then rendering with them in Lightwave. (appears to be taken down.)

Eliza Ra has prepared a brief web page about using image-based lighting in both LightWave 6.0 and in RADIANCE, complete with some sample files.

Arnie Cachelin prepared a more comprehensive tutorial available in the notes for the SIGGRAPH course on Image-Based Lighting.

The reference for the paper that produced these images is:

Paul Debevec. Rendering Synthetic Objects Into Real Scenes: Bridging Traditional and Image-Based Graphics With Global Illumination and High Dynamic Range Photography, Proceedings of SIGGRAPH 98, pp. 189-198 (July 1998, Orlando, Florida). (web page)