[HN Gopher] Ever: Exact Volumetric Ellipsoid Rendering for Real-...
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Ever: Exact Volumetric Ellipsoid Rendering for Real-Time View
Synthesis
Author : alphabetting
Score : 68 points
Date : 2024-10-03 08:07 UTC (14 hours ago)
(HTM) web link (half-potato.gitlab.io)
(TXT) w3m dump (half-potato.gitlab.io)
| alphabetting wrote:
| Impressive video:
| https://twitter.com/alexandertmai/status/1841739387400552826
| xeonmc wrote:
| Neat, the concept is so elegantly obvious:
|
| - your dataset is already an analytic representation of stretched
| spheres. Just assume that they are a hard shape of plasma with
| uniform density throughout the volume.
|
| - for each pixel perform ray intersection against each spheroid,
| the thickness that the ray went through is precisely how much
| thickness the spheroid is contributing light to your pixel
| (obviously also multiplied by solid angle)
|
| - since it's light, there is no occlusion, so just stack the
| contribution from all the ellipsoids together and you're done.
|
| - since you are rendering a well-defined shape without self
| occlusion, there is no random popping in and out no matter the
| angle.
|
| The computation is practically equivalent to rendering CSG
| shapes, except even easier since you only ever add and not
| occlude/subtract. It also scales with rat racing hardware
| directly.
| lufasz wrote:
| I'm actually in the market for some rat racing hardware.
| Anything you'd recommend that won't be obsolete in six months?
| amluto wrote:
| I read this:
|
| > since it's light, there is no occlusion, so just stack the
| contribution from all the ellipsoids together and you're done.
|
| and then I scratched my head at how you can possibly do a
| credible rendering of any real scene without occlusion,
| contemplated that the images in the paper absolutely had
| occluded objects, and then read a bit more and figured it out:
|
| Each ellipsoid has a "density," which is a single number
| indicating the degree to which it absorbs light coming from
| behind it. And this formulation allows the integral along a
| path from infinity to the camera to be exactly evaluated. So
| there _is_ occlusion! It just happens to work correctly even
| when ellipsoids overlap.
|
| [0] It's slightly more complicated, but not much. The raw
| density scales a term in the integral, but this results in a
| poorly behaved gradient, so the trained parameter is more or
| less the opacity when looking through the center of the
| ellipsoid through the shortest axis.
| pavlov wrote:
| It's great how the field of realtime volumetric rendering is
| alive with so many options and new yet simple approaches are
| being invented.
|
| Reminds me of the mid-1990s before everyone basically agreed that
| lots of triangles of any size are the right model representation.
| There were NURBs and metaballs and reyes micropolygons and who
| knows what else... Even Nvidia's first hardware accelerator chip
| used quads instead of triangles (just before Microsoft made
| triangles the standard in Direct3D).
|
| Looking forward to seeing where this settles in a couple of
| years! The intersection of video and 3D is about to get super
| interesting creatively.
| WithinReason wrote:
| maybe something like this:
|
| https://arxiv.org/pdf/2405.16237
| GistNoesis wrote:
| We all know where it's going since 1873. What matters is the
| fun along the way.
| cpldcpu wrote:
| what are you referencing?
| GistNoesis wrote:
| Genesis 1:3 (Unknighted James Clerk Version).
| pacaro wrote:
| As @GistNoesis is being somewhat gnomic, I believe that
| they are referencing
|
| https://en.wikipedia.org/wiki/A_Treatise_on_Electricity_and
| _...
|
| Written in 1873 by James Clerk Maxwell
|
| They also reference Genesis 1:3 "Let there be light"
| yklcs wrote:
| The main selling point of Gaussian Splatting over NeRF-based
| methods is rendering (and training) speed and efficiency. This
| does come at the cost of physical correctness as it uses
| splatting instead of a real radiance field.
|
| This method tries to move back to radiance fields, but with a
| primitive-based representation instead of neural nets. Rendering
| performance seems to be quite poor (30fps on a 4090), and
| rendering quality improvements seem to be marginal.
|
| I'm not quite sure I understand where this fits in when NeRFs and
| 3DGS already exist at the opposite ends of the correctness-speed
| tradeoff spectrum. Maybe somewhere in the middle?
| jampekka wrote:
| Primitive-based representations are a lot easier to manipulate
| (e.g. animate) than NeRFs. Also they can be a lot more
| efficient/scalable when there's a lot of e.g. empty space.
| desdenova wrote:
| I always assumed this was already how those were rendered,
| because that's kinda obvious, and raymarching is a standard
| technique for real-time volumetric rendering.
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