3 ms·

JFA might be multi-pass but the pass-count is logarithmically resolution bound and doesn't depend on the number of "seeds", this cone-rendering stuff creates ov

JFA might be multi-pass but the pass-count is logarithmically resolution bound and doesn't depend on the number of "seeds", this cone-rendering stuff creates overdraw (basically extra passes), as you can read in the article you linked he becomes draw-bound at around 500 seeds. I rewrote my diffusion curve[1] rendering code to GPU the other year and rendering diffusion curves is basically analogous to voronoi rendering (your first pass should be seeding a canvas with the closest source color, then an varying amount of blurring depending on how the distance to the closest source, the max being canvas resolution so it can be done in log(res) passes). Since the curves (ie "voronoi seeds") are splines you want to render them at canvas resolution, so for just a simple circle on a 2048x2048 canvas you're looking at about 4-8k of seeds just for this simple case, but reducing the size of the cone isn't an option (the center of the canvas will have a 2k pixel distance to the closest pixel), so you'd basically be rendering a "large" amount of huge cones. Anyhow I found a solution to the nearest pixel+distance problem by running a couple of repeated axis aligned "run" passes(kind of like flood-filling), had I know of this JFA algo I probably would've used that. I did stumble upon the cone rendering but the overdraw issue concerned me. If I get some time over I should revisit that code and see if JFA would be faster.. the number of passes should be in the same ballpark but JFA should be more paralell since my compute shader had loops and was parallelism bound by each axis dimension. [1] - https://maverick.inria.fr/Publications/2008/OBWBTS08/ https://maverick.inria.fr/Publications/2008/OBWBTS08/

rwbt 4y ago
Not sure if you read the article till the end but > On the same machine, the instancing version can do a few thousand seed vertices (an order of magnitude more) at 60 frames-per-second, after which it becomes bandwidth saturated. If you have a powerful GPU you can get even faster results. I have a project that does Lloyd's relaxation using voronoi and for me the using cones with a depth buffer gave the best result.
- whizzter 4y ago
  Right, in my case the "few thousands" was for a single fairly simple shape (diffusion curves are basically continious line/splines for each shape border, so a single horizontal spline over the screen would generate almost 2k or 4k seeds depending on type at 1080p ). Real diffusion curve images would multiply that by an order or two at the least depending on complexity of the image (the algo I wrote as well as JFA might have a higher fixed number of iterations but it's fixed so the number of seeds don't matter). Besides, GPU's have turned more and more general so even if there's optimizations for the triangle rendering the compute case will probably gain even more from more recent GPUs. Optimizing for GPU's can be funny, and I wouldn't be surprised if the break-point on where the tri-fans are faster is higher than I expect, but at the same time unless it's a tile-based renderer I'm pretty sure there will be a break-point (also tilebased renderers can sometimes fall of performance cliffs in special cases).
  - rwbt 4y ago
    Yes- the drawing cones performance will eventually bottleneck depending on the num of sites, in that case your proposed solution makes much more sense.

rwbt 4y ago

Not sure if you read the article till the end but > On the same machine, the instancing version can do a few thousand seed vertices (an order of magnitude more) at 60 frames-per-second, after which it becomes bandwidth saturated. If you have a powerful GPU you can get even faster results. I have a project that does Lloyd's relaxation using voronoi and for me the using cones with a depth buffer gave the best result.

whizzter 4y ago
Right, in my case the "few thousands" was for a single fairly simple shape (diffusion curves are basically continious line/splines for each shape border, so a single horizontal spline over the screen would generate almost 2k or 4k seeds depending on type at 1080p ). Real diffusion curve images would multiply that by an order or two at the least depending on complexity of the image (the algo I wrote as well as JFA might have a higher fixed number of iterations but it's fixed so the number of seeds don't matter). Besides, GPU's have turned more and more general so even if there's optimizations for the triangle rendering the compute case will probably gain even more from more recent GPUs. Optimizing for GPU's can be funny, and I wouldn't be surprised if the break-point on where the tri-fans are faster is higher than I expect, but at the same time unless it's a tile-based renderer I'm pretty sure there will be a break-point (also tilebased renderers can sometimes fall of performance cliffs in special cases).
- rwbt 4y ago
  Yes- the drawing cones performance will eventually bottleneck depending on the num of sites, in that case your proposed solution makes much more sense.