Live Action & CG for VRay Tutorial

[Infrared digital]

Hi

Does anyone know of a similar detailed tutorial to this one below but for VRay ?

http://eat3d.com/blog/eat-3d/new-dvd...ing-nukex-maya

I want to understand the detailed in's and out's of going from creating the HDRi, shooting the footage to rendering in VRay, camera tracking, compositing (preferably After effects) and everything in between - as technical as possible.

Thanks

N

[joconnell]

No, but you can gather together all the information you need from various other parts of information on the web. I'll start pulling together some links.

[joconnell]

Two things are going to change the way you work - what camera / lens combination do you have and what 3d tracking software are you going to use? Personally I'm using syntheyes for tracking and then using a samyang 8mm fisheye on a cheapy canon slr and a nodal ninja head for shooting my hdris.

[Infrared digital]

Hi Joconnell

Thanks for getting back to me, much appreciated.

I am quite far along with the process but there are some aspects to it that I am trying to iron out, I will list below where I am;

HDRi - Pano Maxx pano head, 15mm Sigma Lens - I am using Photomatix to merge the Raw files and PT Gui to merge to an exr pano. I am having issues with the output of the exr so that the exposure and Tone Mapping is fine tuned as best as possible.

I am about to create a setup for tracking markers with coloured tennis balls spaced out using 4 x 2 metre folding rulers so that Syntheyes can pick up the markers easier. Hopefully this will iron out the tracking problems I am having with Syntheyes and will also provide me with some physical items to scale the scene from.

The camera that I am taking the HDR shots and footage with is a Canon 550D. HDR shots are captured as full res Raw files and the footage is 1080p @ 25fps.

I want to have the footage, hdr and location measurements all calibrated as much as possible so that the scene is as accurate as I can get it in Max and with the VRay Physical Camera. Including Gamma which I am using (or atleast, think I am using the linear workflow correctly).

I use After Effects to composite which was based on your advise in previous threads a long time ago !

Thanks again

N

[joconnell]

Ah okay - one thing that's a pain in the ass is that the vray camera won't play as nice with camera tracks, since all of the trackers output a standard camera only. You might find issues with any tracks that have animated lens values. It's handy that you're shooting your footage on the same camera as you're taking the HDRI's so you've no colour temperature issues. I'd put in a grey ball and a silver ball into your list of stuff to have, and maybe a mini macbeth passport color checker for extra reference.

What type of issues are you getting with your syntheyes tracks?

[Infrared digital]

The real issue I am having is getting the tracked data into max correctly and applied to a VRay camera.

With regard to taking the data into Max to make sure the VRay camera settings are correct ie; Film Gate and Focal Length. I can copy and paste the coordinate data from the Standard camera to the VRay camera but I cannot figure out how to sync the camera settings correctly. Do you know how to do this ?

[joconnell]

Parent or copy paste if something like the horizontal FOV is the same. You might be better off keeping the original track camera and using the vray exposure control in the environment panel though. Lele did a camera conversion script with the code to match a physicam to a normal cam so it's quite possible that we could automate it too.

[Infrared digital]

Ok, managed to sort that by matching the Standard Cam Lens to the VRay cam Film Gate and the Standard Cam FOV to the VRay Cam FOV which is a tick box.

Just wondering, what do you find best to use on set as tracking markers ?

[joconnell]

It really depends. If you're on a green screen shoot then blue crosses so you've got a chance of doing one key for blue and another for green and don't need to roto out anything else. For live action I tend to use nothing if it's in real world circumstances, there's normally plenty of detail to be tracked in the plate. A tracker doesn't give a toss about what it tracks, it just sees the region that you've got selected as a pattern of pixels to try and find in each frame, and this can be anything once you've got enough contrast for it to stand out from the background. If you're tracking an object or a face then any kind of dot that's visible against the object will work fine, you just need to be careful of the amount of motion blur. That said the more motion blur, the looser your solve can be in terms of what you can get away with.

For an object, try and make sure you've got 8 - 12 tracks on screen at all times, and if you've got a choice, make sure that there's enough parallax in how the object moves. Any 3d tracker will have issues with long lenses or shots where the position of the camera doesn't change much, as it relies upon having trackers at different depths sliding by each other to make a mathematical model of what the shape looks like.

Another thing that'll come in handy is if you've got control of the camera you're shooting on, you can always shoot a second take with a totally different camera move, solve for this, and then with a model of the world built you can often tell your 3d tracking app that a tracker in one shot corresponds with another. This means for shots with gentle moves or tripod shots, you can take a much bigger second shot with lots of parallax and use this info to solve a shot that you'd otherwise get a crap result from.

[joconnell]

Oh, that's a fair point. Since you can track anything, put stuff into the shot that looks like it belongs there naturally, so you don't have to pain anything out after.

[Infrared digital]

I appreciate your comments although I will be doing basic environment footage so, nothing too hectic.

Do you do anything to the footage before tracking it for example, sharpening it or bumping up the contrast ?

[joconnell]

Nada. Syntheyes has some sharpening bits built in to it but by and large I'll use whatever the footage is. For small markers on film or on really high ISO footage shot at night a small blur might help but I've been lucky to work with footage shot by fairly decent DOP's over the years. The only thing that may help if you're on a dslr is removing rolling shutter, and syntheyes has that built in now too.

[Infrared digital]

How much of a factor is the rolling shutter ?

[joconnell]

It depends on what the camera is and how fast the camera moves. You can get very jellyish effects that render the footage possible to track, but if you're putting in 3d bits that cover the full height of the frame you're going to have a lot of issues trying to get straight lines to match up properly. There's definitely a garbage in / garbage out rule with tracking and comping, if you start out compromised then you've got to bring your work down to the level of the footage which is a shame.

[Infrared digital]

What software do you use to process the HDRIs?

I have tried so many processes but can't seem to arrive at one that I am happy with. The main one is to start in Lightroom then go to Photomatix but it does tone mapping etc.. to it which I don't want but, in order to get a 16 bit tif out of it, the tone mapping has to be done.