This patch implements a new Gabor noise node based on [1] but with the
improvements from [2] and the phasor formulation from [3].
We compare with the most popular existing implementation, that of OSL,
from the user's point of view:
- This implementation produces C1 continuous noise as opposed to the
non continuous OSL implementation, so it can be used for bump
mapping and is generally smother. This is achieved by windowing the
Gabor kernel using a Hann window.
- The Bandwidth input of OSL was hard-coded to 1 and was replaced with
a frequency input, which OSL hard codes to 2, since frequency is
more natural to control. This is even more true now that that Gabor
kernel is windowed as opposed to truncated, which means increasing
the bandwidth will just turn the Gaussian component of the Gabor
into a Hann window. While decreasing the bandwidth will eliminate
the harmonic from the Gabor kernel, which is the point of Gabor
noise.
- OSL had three discrete modes of operation for orienting the kernel.
Anisotropic, Isotropic, and a hybrid mode. While this implementation
provides a continuous Anisotropy parameter which users are already
familiar with from the Glossy BSDF node.
- This implementation provides not just the Gabor noise value, but
also its phase and intensity components. The Gabor noise value is
basically sin(phase) * intensity, but the phase is arguably more
useful since it does not suffer from the low contrast issues that
Gabor suffers from. While the intensity is useful to hide the
singularities in the phase.
- This implementation converges faster that OSL's relative to the
impulse count, so we fix the impulses count to 8 for simplicitly.
- This implementation does not implement anisotropic filtering.
Future improvements to the node includes implementing surface noise and
filtering. As well as extending the spectral control of the noise,
either by providing specialized kernels as was done in #110802, or by
providing some more procedural control over the frequencies of the
Gabor.
References:
[1]: Lagae, Ares, et al. "Procedural noise using sparse Gabor
convolution." ACM Transactions on Graphics (TOG) 28.3 (2009): 1-10.
[2]: Tavernier, Vincent, et al. "Making gabor noise fast and
normalized." Eurographics 2019-40th Annual Conference of the European
Association for Computer Graphics. 2019.
[3]: Tricard, Thibault, et al. "Procedural phasor noise." ACM
Transactions on Graphics (TOG) 38.4 (2019): 1-13.
Pull Request: https://projects.blender.org/blender/blender/pulls/121820
4f51033708