Sunday, 21 April 2013

Lighting: HDRI

To light the cinematics, I decided to use image based lighting in Maya as a starting point. To do this I needed to go out on location and take pictures of a light probe at different exposures to get the required lighting information. I went the the woods at Stansted Forest on two different occasions when the weather was different to get a unique HDR image for each scene.

For each scene I took 19 photos of the light probe at different exposures in order to get an accurate HDR image.

Below are image of the HDR image working in Maya for the summer cinematic. The first image shows it working in the viewport and casting light on the cube, and the second shows a rendered metallic sphere reflecting the image back.

Before taking the HDR image into Maya though, the photographs must first be converted into a HDR file using Photoshop and HDRShop. To do this I opened Photoshop and selected File > Automate > Merge to HDR Pro and selected the photos. Photoshop then automatically aligns the photographs in case the tripod was knocked when taking the images. 

Once this is done, the image needs to be cropped down to a square containing the light probe and saved out as a HDR image. I then opened this file in HDRShop and selected Image > Panorama > Panoramic Transformations. The image must be converted from a Mirrored Ball to Latitude/Longitude, and then saved out again as a HDR file.

This stretches out the image onto a rectangle which is then opened up again back in Photoshop. The final step is to paint myself out of the image before saving it for a third time as a HDR, ready to be opened in Maya.

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