11.7 - Procedural Texture Mapping (2)¶
Texture maps that simulate the surfaces of real world objects such as cloth, wood, marble, and water can be created with just the right mixture of gradients, patterns, and noise combined at different scales. However, finding the correct mixture for a specific “look and feel” is non-trivial. The job of a “texture designer” is to find the right combination of these methods for a specific situation. Take special note of the “visual effects artists” in the trailing credits of any movie that contains computer graphics imagery (CGI). It takes very talented people who have both technical and artistic talents to design procedural texture maps.
This lesson introduces some resources for further investigation into procedural texture maps. If this topic has peeked your interest then these resources would be a good place to start additional studies. However, if you are using this textbook for a course, you should probably skip this lesson and return to it at a later time.
Shadershop¶
Toby Schachman has created a very cool tool called Shadershop. It allows you to combine functions in interesting ways and see the results in both visual and equation format. A description and video tutorials for Shadershop can be found at http://tobyschachman.com/Shadershop/. The actual tool is web based and can be used at http://www.cdglabs.org/Shadershop/.
There are many ways to combine functions and Shadershop will help you better understand the possibilities. For example:
- add functions,
f1(x) + f2(x) - multiply functions,
f1(x) * f2(x) - compose functions,
f1( f2(x) ) - minimum,
min(f1(x), f2(x)) - maximum,
max(f1(x), f2(x))
where f1(x) and f2(x) can be any function from a large
set of possibilities, such as sin(), floor(), abs(), etc.
Useful Functions¶
Several researchers have created lists of foundational functions for the generation of patterns. Check some of them out:
- Golan Levin :
- Polynomials : http://www.flong.com/texts/code/shapers_poly/
- Exponential : http://www.flong.com/texts/code/shapers_exp
- Circular & Elliptical : http://www.flong.com/texts/code/shapers_circ
- Bezier and Parametric : http://www.flong.com/texts/code/shapers_bez
- Inigo Quilez : http://www.iquilezles.org/www/articles/functions/functions.htm
- Jari Komppa : http://sol.gfxile.net/interpolation/index.html
Graph Toy¶
Another nice visualization tool for complex functions is Inigo Quilez’s “Graph Toy” at http://www.iquilezles.org/apps/graphtoy/. Note that you can enter any complex equation into each of 6 function edit boxes and plot them on top of each other.
Book of Shaders¶
Patricio Gonzalez Vivo has created an excellent interactive textbook on shaders called The Book of Shaders. It will take you significant time to work through the entire book, but it has great content.
Other Resources¶
- A lesson on OpenGL ES shaders:
https://www.raywenderlich.com/70208/opengl-es-pixel-shaders-tutorial - A series of lessons on surface properties and shaders:
http://content.udacity-data.com/cs291/notes/UdacityLesson9ShaderProgramming.pdf - An amazing example (with source code):
http://reindernijhoff.net/2015/05/rendering-a-planet-with-two-triangles/ - WebGL halftone shader:
http://webstaff.itn.liu.se/~stegu/webglshadertutorial/shadertutorial.html - Beyond Programmable Shading (SIGGRAPH course on things more advanced than
programmable shader programs)
http://bps12.idav.ucdavis.edu/