Better Pseudo-Depth of Field

[richardrosenman]

Hi Kram;

Truthfully, I never understood why the blue channel contained the velocity and not the depth. However, using only 2D values seems to be 'good enough' to mimic 3D motion blur. It seems to be slightly different per application. I use 3dsmax and this post explains that the blue channel isn't even used for velocity - it's discarded, which isn't how it used to work for me. So perhaps it really is variants based on different apps:

http://www.timsportfolio.co.uk/tutorials/velocity-pass-3ds-max/

I can say one thing. We've tried all sorts of motion blur tricks and they rank in different spots on the totem pole:

3 - ReelSmart motion blur (frame analyzed and derived motion blur) - rarely works well and excels in slow moving  frames only. Also, the higher the resolution, the better the results.

2 - Velocity map / 2D motion blur. Better than above but unfortunately tends to destroy and degrade the image. Often over-exaggerated.

1 - True 3D motion blur. Simply the best.

I remember doing this spot in 2005 for Diet Pepsi to be screened during the Academy Awards:
http://richardrosenman.com/project/?cid=37



We had hundreds of bottles and cans stuck in a fridge, rendered with full global illumination, hybrid 2D/3D depth of field and 3D motion blur. Frames were averaging 12 hours each. There are 24 frames a second. And 30 seconds for that spot...
 
-Rich

[kram1032]

Yeah, true 3D motion blur should be the way to go.
Though what difference could it be, for computers of today, to change that into a 4D or 6D problem, using the full x,y,z-depth (or just z-depth) and x,y,z-velocity?
Of course I do not have experience in this but it seems to me that this kind of convolution should be much easier than the reverse problem of deconvolution (e.g. DoF- and Motion-deblurring)

[lycium]

Exactly. BUT, and there's always a but. Motion blur, dof, etc, is free in unbiased renderers (Maxwell, Octane, Arion, etc)

I have some issues with Octane's claims to being unbiased, and wonder why you don't include Indigo Renderer on that list

unfortunately, those are still not viable options. They still take waaaaaay too long when compared to biased renderers and those that utilize GPU processing, have some serious limitations which prohibit their use for any serious commercial production. For instance, depending on the project, it is not uncommon to have geometric scenes in excess of millions or billions of triangles. This is immediately impossible with GPUs. Likewise, using 4k textures, or many of them is also a limitations due to GPU ram. There's much more.

That's a long list of nuanced claims, addressing them all would take ages :S Of course I'm biased from working on unbiased rendering software, but geometric detail seems fairly well addressed to me with instancing and 3GB or 6GB GPUs. Indigo's hybrid CPU+GPU acceleration only stores the geometry on the GPU, so you can really get a lot on there...


In any case, if motion blur and DOF are your only concerns then something like stochastic rasterisation is probably the most efficient algorithm. However, some of us also want "perfect" global illumination and handling of light scattering events, so there's really nothing for it but Monte Carlo methods

[richardrosenman]

Doh! How could I have forgotten Indigo - it's AWESOME!

-Rich

[kram1032]

Of course I'm biased from working on unbiased rendering software

I see what you did there

[lycium]

you should post some new indigo work sometime mark   haven't seen you on the forum in aaages!

[kram1032]

Yeah, I know...
Haven't done any work with it in aaages either
Or with Blender for the most part...
It's a mixture of not knowing what I could do and not having time... - mostly the first part though.