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Coming in V-Ray Tuner 2.2: Exposure Round-Tripping for Fast Lighting Tweaks

Some of you have probably seen me using the per-light rendering features of V-Ray Tuner, since it gives me a lot of control over a complex light setup without having to re-render, similar to Maxwell Render’s multilight feature. But, seeing it in action, you probably also thought to yourself “that seems slow and impractical for animation.” Well, I’ve finally implemented something I’ve been meaning to do to enable you to roll your exposure settings back into Maya from Nuke tweaks so that you can do a draft per-light rendering, hone your light balance and then take those exposure settings from Nuke or Photoshop and then input them to change each light’s value in Maya. Then you render a single final image that has perfect lighting. If you work on product shot type things, this workflow will save a ton of time in the long run:

In Nuke, you set the Exposure values to Stops to emulate F-stops, then adjust your exposure to make the lighting exactly as you want it and then, once you have a balance of lighting that you like, go back to Maya, select your V-Ray light and then run the Per-Light Render Exposure Tweak script from the Utilities menu and enter each exposure value into the field with the respective light selected.

As I mentioned above, it also works in Photoshop. Pick your per-light images in the File/Scripts/Load Images Into Stack dialog and they will all load into a layered document:

Set each layer to Linear Dodge (Add) and add a clipped Exposure adjustment to each (by alt clicking between the layer and the Exposure adjustment):

And the workflow is much the same as in Nuke:

That has the exact same exposure settings as the Nuke exposure and looks just like our final flat render. The cool thing about the Photoshop method is that you can flatten your Exposure tweaks into each layer and do another round of exposure edits without having to render out more per-light passes. Obviously, you need to use 32-bit renders for this to work effectively since 8- and 16-bit ones aren’t floating point and degrade with exposure edits.

I just need to update it to work with meshes and V-Ray Light Materials. Thanks go out to Will Earl who helped explain the math of the exposure conversion to me.

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