Live Action & CG for VRay Tutorial

[joconnell]

PT gui for me over here, or if you wanna try something free http://hugin.sourceforge.net/ can be good too!

[chriserskine]

ptgui, is worth getting. if your going to be doing a bit of it.

photomatrix can output full 32-bit exr's. you don't need to worry about the tonemapped ones. though they can be useful for stitching.

ie, lightroom to photomatrix, outputting both a tonemapped and full hdr files.
then stitch the tonemapped files in ptgui (pick up more control points than a full hdr) but don't render this. instead save out a template file.

then load up a new ptgui scene with all the real hdr files, apply the template that was just made and hit render.

or you can just stitch all the bracketed photo to hdr just in ptgui. though it take quite a bit longer to process so it worth going via photomatrix.

[Infrared digital]

When exporting the Exr and Tif files from Photomatix, there is quite a difference between the two images - usually the Tif is correctly exposed but the Exr is alot darker. This is odd because the initial tone mapping that I do in Photomatix looks correctly exposed.

[Infrared digital]

This has me stumped. Lightroom does an amazing job removing the chromatic abberation but when I use the plugin to link with Photomatix - it only allows me to save out a 16bit tiff and not an accompanying Exr.

I have also just realised that Lightroom doesn't open Exr files !! Good Gawd.

[chriserskine]

lightroom has very poor hdr support. and only in the newest version. it only supports 32-bit tif files. no exr, no hdr.

I've never used this. basically you start in lightroom but you can't use it for any hdr stuff.

the exr file from photomatrix shouldn't have any tonemapping applied. you don't want it if your going to light 3d scenes with it.

an overexposed exr file should be fine to use. you can adjust them in 3dsmax/vray.

in ptgui though you can adjust exposure for viewing them, but its best to feed it a correctly exposed image or even an averaged out tonemap to find control points. then save out template and replace with the exr's and render. it won't matter what the exr's look like at this point. as long as they are linear and have all the information there they will be fine.

[Infrared digital]

What I don't understand it that when I export the Jpeg and the Exr from Photomatix the two images are at different exposures with the jpeg correctly exposed. I appreciate that the Exr has much more information however, when I open an Exr from any other source for example VHDRI_Cloudy08.exr from Hyperfocals VHDRI library - it is correctly exposed. My Exr is underexposed.

[Infrared digital]

What I don't understand is that when the Jpeg's and Exr's are exported from Photomatix the Jpeg's are correctly exposed while the Exr's are underexposed. I know that there is alot more information in the Exr's but when I look at Exr files from other sources for example; Hyperfocal's VHDRI's the Exr opens in Photoshop looking correctly exposed. My Exr is underexposed.

It can be brightened in Photoshop using adjustment layers to bring it to the right exposure but, I am not sure if this is the best thing to be doing.

[chriserskine]

shouldn't be an issue to just change the exposure of the exr file in photoshop. the 32bit float file is able to hold a lot more information than your going to use with a bracketed set of photos. so i wouldn't worry too much about it.

dose the jpeg have any renaming done? it should have something about which tonemapping setting used added to the name.

its only applying the tonemapping to the jpg, hence its looking like the right exposure.

also keep in mind when you bring it into max that your hdr file is gamma 1.0 (or adjusting to taste for more shadow contrast etc..) and your other jpg textures are gamma 2.2. how you set this up depends of your workflow, but make sure you just don't treat them all the same.

[Infrared digital]

Hi Chris

I have been able to take some more HDRi's and was wondering if you could have a look at this comparison ?

The three exposures below are from the most recent HDRi that I took. It shows three exposures using the 32 bit Exposure Slider in Photoshop so it isn't exact. My question is, if you compare my exposures to those of the image exposures below, the sun in the one below is still very bright when considerably under exposed. Is this something to be concerned about ? I shoot 8 brackets 2EV's apart. As I use Magic Lantern I could go to 9 exposures but the last exposure can take a long time. Maybe this will sort out the problem however, I just need to get out and do more tests to see.



The HDRi below is from a reputable online retailer and is only used for comparison purposes.



Many thanks for your help.

Niall

[joconnell]

A lot of folks use an ND filter or one of the higher end cameras in that type of weather just so you get the 1/8000 sec shutter speed - does it make much a difference to your end render or are you looking at making commercial HDRIs?

[Infrared digital]

Hi John

I am trying to create the best possible HDRI's with the equipment that I have which is a Canon 550D. Maybe I might want to sell them but my goal is to create them for usage in professional VFX.

Regarding the shutter speed the 550D only goes up to 1/4000 sec so, maybe that's reducing the brightness of the sun.

Incidentally, while you are here, I am doing the whole process from HDRi capture to rendering in VRay and compositing in After effects. There is so much information our there but to get your opinion would be great. What render elements do you save out ? I have found that using the RGB as a base then adding slight adjustments with reflection, specular, shadow etc... to be an excellent workflow for stills but with video, I think I need the full flexibility for adjusting everything.

[joconnell]

All good - I'm on a 600d so I've the same as yourself and I haven't had any problems with my hdri's so far. I'll start doing a few more bits on vfx integration but as ever if you've any specifics then stick them down here and I'll get back to you asap.

[Infrared digital]

Thanks for your help John !

I supposed firstly, how do you know if you have a good HDRi - is there a way to tell ? Do you separate yours out to high-res for reflections, mid-res for environment (or whatever) and low-res for lighting ? Or do you just use one for all ?

The other main question is regarding the render elements. I have used them alot but was hoping to know from seasoned professionals, the best way to go about compositing from VRay to After effects.

Below is a link to a recent test - its really just for process so disregard the content !

http:////player.vimeo.com/video/5810...Vimeo</a>.</p>

I am rendering out to 16bit tif files so the space required for them is huge especially when using multiple render elements.

[Infrared digital]

I checked the 32bit color picker in Photoshop and it tells me that my HDRi has 8.42 stops. It actually has 8 but that is close enough for me. With regard to the other HDRi, it says that it has 14.06 stops so that must be why its sun stays brighter for longer.

The other thing I am looking at are render elements and how do you export them ? 16bit Tif or 32 bit Exr ?

[joconnell]

Exr into nuke for everything here - the file sizes are really small so it works well. In terms of the stops for the hdri I was normally shooting 7 images about 1.5 - 2 stops apart but that's pretty arbitrary. As with yourself the only one that'd really matter is the 1/8000 in the case of bright sun. In here we've actually been painting out the sun in our HDRI's and then replacing them with a direct light instead - it gives us more options in our shadow passes and also in the overall balance between light and shade. In the current show there aren't many objects that are really glassy so there's no need for extremely high res HDRI's for the sake of crisp reflections. Normally I downres them to either 1024 x 512 or 2048 x 1024 for the sake of keeping memory overheads low.

In every shot we get to do, we have a colour chart and a grey ball / silver ball as reference. The colour chart is to know if the camera or the light has tinted the footage in any way and as a reference for neutralizing the plate. The silver ball is a really handy one to make sure the rotation and placement of our HDRI is correct so the light and reflections are coming from the right angle, and the grey ball is likely the most important one as it lets us know the colour and ratio of the direct light to the ambient bounce light. The grey ball is a 50% gray - taken from the 50% grey from the colour chart (get one in a photography shop) and then you can make a grey ball in vray and try and match it to the reference one shot in your plate.