GPU Texture Sampler Bezier Curve Evaluation

Below is a paper I submitted to jcgt.org that unfortunately did not get accepted. Maybe next time!

The main idea of this paper is that bilinear interpolation can be equivalent to the De Casteljau algorithm, which means that if you set up a texture in a specific way, and sample from it at specific texture coordinates, that it will in fact give you Bezier curve points as output! It scales up for higher dimensional textures, as well as higher order curves.

The image below shows this in action for a cubic Bezier curve (3 control points) being stored and recalled from a 2×2 texture (there is actually a curve stored in each color channel).

This image is from an extension linked to lower down which applies the technique to surfaces and volumes:

The primary feedback from the reviewers and editor was that:

  • It was an interesting technique and they thought it was a paper worth reading.
  • The usage case was fairly limited though – basically only when your are compute bound in your shader program, and have some curve calculations to offload to the texture sampler. Or if you are already using a lookup texture and would benefit from fewer instructions and smaller lookup textures.
  • It could have been shorter due to the writing being shorter, but also it could have been less thorough. For instance, it didn’t need to show equivalence to both the De Casteljau’s algorithm as well as Bernstein polynomials, since it’s already known that those are equivalent.
  • They wanted some more performance details

I agree with the feedback, and don’t feel like taking the time to change and resubmit or submit else where, so I’m sharing it here on my blog. I hope you enjoy it and find it interesting (:

Here is the paper:
GPUBezier2016.pdf

Here is the supplemental materials (opengl and webgl source code):
SupplementalMaterials.zip

Here is the webgl demo from the supplemental materials, hosted on my site:
GPU Efficient Texture Based Bezier Curve Evaluation

Here are some working shadertoy demos of the technique:
Shadertoy: Mystery Curves – Quadratic
Shadertoy: Mystery Curves – Cubic
Shadertoy: Mystery Curves – Quartic
Shadertoy: Mystery Curves – Quintic

Extensions

Continuations of this work:

Failed Experiments

Continuations that didn’t work out:

What are your thoughts? Is this cool? Is it lame? Got some ideas to improve it? Leave a comment! (:

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About Demofox

I'm a game and engine programmer at Blizzard Entertainment and have been making games since 1990 (starting out with QBasic and TI-85 games) My shipped titles include: * Heroes of the Storm * StarCraft II: Heart of the Swarm & Legacy of the void * Insanely Twisted Shadow Planet (PC) * Gotham City Impostors (PC, 360, PS3) * Line Rider (PC, Wii, DS) I also like hiking, making music, learning cool new stuff and attempting the impossible.