Tiled EXR/Workflow

[Macker]

Hey guys,

I was just participating in a discussion about 16bit vs 8bit images over at cgarchitect and one of the guys there brought up tiled exr's. I am familiar with the concept (to a degree) but have no idea about the workflow, or even its real-world benefits.

Firstly; is it enough to simply use the Vray bitmap to Vray HDRI converter (with convert to tiled exr checked) on a scene to impliment this, or are there other requirements that I am missing?

Secondly how big an impact will this have on 1. Render times, 2. RAM usage and 3. Texture filtering/antialiasing?

Personally the RAM usage is the most interesting part to me.

Also, what is the "best" compression method/tile size to use?

Thanks,


Chris

[joconnell]

So. The vray hdri loader has far better filtering than the standard bitmap loader so you'll get smoother renders. The second thing is that if by tiled exr you mean multires exr (which the bitmap to multires convertor will do) you can get huge memory benefits. When you convert to a multires exr, you get a single file, but the file contains the original res image, a half res version, a quarter res version, an eight res version and so on. When the render is loading your texture, it know how far away it is and will only load a version that's high enough quality for what the render needs and no more, so if you have shots where you've got objects very far away that come close up to camera, you can have a single texture that will be efficient for the far away parts and high quality up close.

[Macker]

Superb, so the converter will do all of that without any real intervention from me?

[edit] Just converted a scene and one jpeg has gone from 46Mb to 807Mb! Another has gone from 54Mb to 316Mb... I appreciate that only the tiles that are needed are loaded so this will help, but surely if the file size is increasing that much then when the full sized versions are loaded then it's going to cause bigger RAM issues than I would have had with a jpeg?

Would it be worth reconverting the textures to half float?

[chriserskine]

there are .tx files too which are multires 8bit tif files.

but I've never got it going since i couldn't find a good convertor for it. though I was on vray 2.5 so maybe something in vray 3 for this?

[Macker]

Sadly there's no 8 bit option in the vray implementation of it. They direct you to an open source converter.

[joconnell]

I'm not sure if the vray menu convertor will do multires, the tool in your start menu > vray adv > tools definitely will, I'll have a fish about in the script to see what options it uses but maybe someone from chaos can confirm.

[Macker]

The script does say "convert to tiled exr", but neither the script nor the .exe (which the script uses) give you an option to use an 8bit format. Seems a bit crazy to me to go from an 8 bit image to 32 bit floating point without adding any additional detail - all you get is massive files.

[joconnell]

Sure. There's an option for 16 bit half float but as you say, exr doesn't have 8 bit as part of it's specification.