For this class I will experiment with a 30 inch cube light tent and two big lights. The idea is to shoot an HDR panoramic photo inside the tent, then rebuild the tent geometry in Maya, and do a spherical projection of the HDR in order to verify we are getting true inverse falloff from our HDR lighting image. In addition I will shoot the tent under different lighting conditions so we can flip textures to turn lights on and off.
This is a great presentation of HDR panos projected on 3D scanned and rebuilt set geometry for the film Beautiful Creatures.
Show the photos and basic workflow for shooting a panoramic using fisheye lens, Nodal Ninja, table tripod, ProMote for exposure brackets, and Nikon D40. In this example I shoot 6 times around, 2 up zenith, 2 down nadir, and 7 exposure brackets from 1/2500 to 1/2.5 or 2EV’s per step. We will shoot with a variety of lighting conditions, but identical everything else (basically turning lights on and off), giving us 70 RAW photos per pano.
Very fast description of viewing the photo sets in Adobe Bridge and the Hybrid stitching workflow as described in “The HDRI Handbook 2.0 by Christian Bloch. Merge each exposure bracket into HDR image and tonemapped jpeg using batch Photomatix. Then stitch only the 10 jpegs in PTgui for faster software response. Once you have a great stitch, you swap in the 10 HDR images, and PTgui will process them together much faster. This workflow breaks up the work and makes it faster for interactive parts and more automatic for the mindless batch parts. Helps when you have lots of panos.
http://www.hdrlabs.com/news/index.php
http://www.hdrlabs.com/news/index.php
In Nuke show how to use the Spherical transform node to paint out the tripod from you pano. Also some white balance and possible boosting of the gain to increase light values. To have later with user_ibl_rect, crop cut out each light and export out as HDR texture. Light extraction.
In Maya do a comparison of a model rendered with this HDR on a typical spherical IBL and the same pano mapped onto the 3D model of the light tent which should allow us to have accurate inverse falloff of light.
Set up two area lights with user_ibl_rect that will generate direct lighting and shadows, allowing us to depend less on Final Gather. You may need to add light relative scale = 0.318 (the reciprocal of Pi) in the string options for this feature.
In addition we will try to use direct lighting (we want good shadows) with these HDR textures by using either user_ibl_rect (maya 2013) or builtin_object_light (maya 2014)
If you are using Maya 2013, this is the method we will cover here.
Introduced with mental ray 3.10 are new shaders called the user_ibl shaders.
Inside this shader package are two new shaders with different usage scenarios.
- user_ibl_env
- A more simplified usage than the Native IBL (mental ray), the user_ibl is a scene entity used for lighting a scene globally from an environment.
- user_ibl_rect
- A shader used to generate light cards or “billboards” to replace otherwise complex geometry and lights in a scene.
Try user_ibl_rect, just attach as light shader to your MR area light, it can illuminate and cast shadows. Also use the connection editor to connect user_ibl_rect Samples -> areaLight areaHiSamples and areaLoSamples. Must have “use light shape” ON, and visible.
If you are using Maya 2014, we will not cover this now, perhaps next week when I upgrade.
mental ray 3.11 includes a new shader called the builtin_object_light that tells mental ray that the object is a light.
Animate lights turning on and off by using the blend mode to dissolve through our identical but different light condition HDR textures.
Drop in some animated creature and hope for the best.
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