Simulate Reflections Of Live Action Character

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  03 March 2013
Arrow Simulate Reflections Of Live Action Character

Quick question - How would one go about simulating reflections of a live character that walks around shiny vehicles. The HDRI maps would take care of the scene reflections but how do you get the live (moving) guy to reflect in the CG objects, especially if they're very shiny. Imagine the guy walking among shiny big objects on all sides?

From the research I did there are 2 options:

1. Put cameras around the guy to "catch" the angle then twist and map it on the geometry.... Problem with this is how do you put the cameras so they're not in the shot while also catching the right angles - and also version may need quite a few cameras.

2. Do a CG model of the guy matching his moves and have that reflected. This option may require quite a convincing model pending on how clear the reflections are - especially if you're talking silver like coating on the CG vehicles.

Can anybody that has some sort of experience in this area give me a heads up on these 2 scenarios or maybe you have a third option.

I'm new to this and I'm just trying to figure it out before going down a road that leads nowhere

Many Thanks...
  03 March 2013

Sigh...I am guessing at would need to have video from the back of the person as well as the front. Then, possibly, figure out how to play / a roto-scoped version of the back view with the HDRI.

You might also (and this is probably more realistic) use something like composite to alter the reflection channel of the EXR file from the render...

Actually curious myself how this would be done if my suggestions are in correct (that happens a lot with me :P )
Randell Trulson
  03 March 2013
You usually have a witness cam either shooting directly, or shooting a mirror if it can be easily cleaned out and the lighting/DoP allows for it and, ideally, it catches a blue/green screen in the background, but it's a helluva lot less common and a lot more trouble usually, only seen it done a handful of times.

It's very, very hard to tell the reflection of a distorted, matted witness cam footage apart from a real one, you often get away with a lot.

Building and mapping a quick 3D model texture with some quick (polarize filter on) references of the person in the lighting he will receive is also an option, but only if the angles change enough that witness footage will start looking too weird.

You get away with more than you seem to think one would
Come, Join the Cult - Rigging from First Principles
  03 March 2013
Thank you very much for both replies. I needed the feedback to know where I'm going with this

Originally Posted by ThE_JacO: It's very, very hard to tell the reflection of a distorted, matted witness cam footage apart from a real one, you often get away with a lot.

The objects I'm talking about would be shiny... silver plated like materials.

The camera would be dollying and panning and this would require the witness cam (or cams) to adjust on the fly. Add to this more than just one reflective object in the shot and I get the feeling it would get too tough to keep coherent... or feasible as it would probably require a lot of cameras for each point of view.

It would seem that building a model of the character (probably lower rez) and then animating it to sync with what the actor is doing would probably be the answer.
  03 March 2013
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