Semi-Procedural Textures using Point Process Texture Basis Functions
EGSR 2020 (Eurographics Symposium on Rendering)
CFG (Computer Graphics Forum)
Submission ID: 1018
Metalmodel of Textures
This supplemental material provides additional information on the core elements of the PPTBF model, i.e. the point process, the window and feature functions.
Texture Representation
Observation of texture databases, e.g., the well-known Brodatz album [Brodatz 1966], reveals that many natural textures embed spatial stochastic structures like cells, cracks, grains, scratches, spots, stains or waves, with some spatial geometric variations. Most of these types of textures can be characterized through three components: 1) the distribution of its elements, which can be modeled as a spatial point process, 2) the local visual pattern of the elements, modeled as a feature function and 3) the interaction among elements, i.e., how they blend with each others or stay localized in isolated regions, modeled as a window function.
Convolutional Model
Observation of texture databases, e.g., the well-known Brodatz album [Brodatz 1966], reveals that many natural textures embed spatial stochastic structures like cells, cracks, grains, scratches, spots, stains or waves, with some spatial geometric variations. Most of these types of textures can be characterized through three components:
- [1] the distribution of its elements, which can be modeled as a spatial point process P,
- [2] the local visual pattern of the elements, modeled as a feature function F
- [3] and the interaction among elements, i.e., how they blend with each others or stay localized in isolated regions, modeled as a window function W.
Artists Texturing Tools
This supplemental material provides additional information on reverse engineering procedural textures designed by artist from the Substance Designer tool.
Substance Designer sample: fish scale
As can be seen from the node graph, artist started to create a pattern of a single fish scale, then use different tiling generator to distribute it on the plane, by mixing (i.e. blending) distributions. The main drawback is the lack of control of the resulting distribution.
Substance Designer sample: lava flow
As can be seen from the node graph, artist...
PPTBF Model
The key idea is to separate the structure synthesis from the color synthesis. Structures can be modeled as procedural modeling, inspired from Blumenthal implicit fucntions and the signed distance field distance functions demoscene (e.g. NVScene, shadertoy) and VFX industry.
Comparisons to Previous Models
We compare to:
- Sparse convolution noise
- LRP Noise
- Cellular texture basis functions
- Texture bombing
- Patch-based approaches
Window Functions of Patch-based approaches
From left to right: (1) input exmplar, (2) output grid of selected patchs from input (patch contents are the features, the grid is resulting from a point process with regular distribution), (3) optimal cuts between overlapping patches [regions delimited by cuts are the windows], (4) resulting synthesis.
Point Process
The Point Process P controls the spatial distributions of elements through 2 parameters:
- tiling: tile the plan in different configurations
- jitter: add some jittering in cell
| Tiling | Jitter |
Window Function
- Cellular Window
- Tapered Cosine Window
|
Cellular Window |
Tapered Cosine Window |
Feature Function
- Anisotropic Gabor Kernels
- Operators: bombing, voronoise
|
Anisotropic Gabor Kernels |
Operators: bombing, voronoise |
Spatial Transformations and Deformations
Visual Structures: thresholding PPTBF
| Binary Structure Maps (thresholding) |
Texture Representation
Few samples of structures generated with PPTBF. These images have been obtained by binary thresholding. Unlike noise, PPTBF covers a large variety of different structural appearances.
Toward Complex Structures: Mixing Cellular and Regural Windows
Complex structures can be obtained by mixing cellular and regular windows (left: no blend, middle: 50%, right: 100%).