Repeating patterns based on numerical formulas.
If you have any confusions on what these are, do a search and read a little about them on the web. Simplified - computer generated patterns mimicking real-world materials such as stone, wood, marble, etc.
Procedural Textures are your friends!
They wrap around your objects seamlessly (if they are the 3D type) and can add some wonderful looking visual effects to your images. You can scale them and manipulate them in many ways - making therm more dense, less dense, change the color, etc, etc.
Procedural Textures are your enemies!
By their nature, procedurals are a computer generated pattern. We have all seen the computer generated 'natural' materials and quite honestly they can look overly predictable and obviously generated on a computer. The repeating patterns are too symetrical and while some procedurals have capability to randomize their look, they can still look fake and visually boring.
This tutorial will attempt to suggest some ideas on how one might randomize these potentially wonderful procedurals and make them at least a little more believable. These ideas are basically how I would approach the subject and not any attempt on stating the 'right' way to do any of this. This approach works for me ...and I hope you can gain something from it also.
This is the scene from which some of the technique I will be discussing has come from. Download it and have a look at all of the materials and how they were created.
These are the objects which use the material in the scene. I am using Rendering Preset P2 for this tutorial - it is used to keep the render speed up.
Let's take one of these objects and start from the beginning - assign an Advanced Brazil Material, set the reflectivity up a little and bring in a Marble Texture into the color slot...and this is what we now have! Somewhat of a bovine looking material:-) Notice how the procedural is mapped on each surface and not 3D looking at all.
The first thing to do is to check the WCS box in the Marble Texture - it's right down near the bottom. It Stands for World Co-ordinate System - XYZ and now maps this texture in 3D to the 'world' of your scene.
Notice the size of the pattern has dramatically changed. It almost looks like a granite.
Scaling the Marble noise
This is the scaling I used for the scene. At times, unfortunately, it is a lot of trial and error to get it to look just right but also allows one to thoroughly grasp the effects of one's actions by examining these changes. One does learn a lot by getting their hands dirty 'so to speak'. The Repeat fields are where one scales the noise to fit the object and the scene. I ended up using .06 in each of the numerial repeat fields. Try some different ones - see what it looks like.
Marble Appearance Settings
Size was left at default of 1.0
Vein width at .31 - this gave me a look closer to what I was after with the veins. Try a few different sizes.
Blur at .51 - the blur effect will harden or soften the transaction from your two colors.
Noise at 3.37 - this control randomizes and adds some nice organic grit to the veins. Too much...and well, it looks like too much!
The results are a little more natural but continue to be predictable in patterning. Our stone is on the way but still looks orderly and procedural - not random and organic enough to sell the look.
When I began putting together the materials for this tutorial I never started out to make a 'marble' material but used the Marble Texture as a building block to making a believeable stone/marble material. I'm quite certain I could have spend much more time fine tuning all of the settings to get a closer reproduction of what a generic marble might look like but, for the purpose of this tutorial, that direction was not followed.
Let's break up these Veins
The Noise Texture in Brazil is great - this one has a variety of different noises within the Texture and gives plenty of control to randomize the look dramatically. So the idea is to break up these veins even more...and also break up the base material too.
We have two color slots in the marble texture. Let's put the Noise Texture into each of these slots and see where it takes us.
Rendering the image - the marbled/veined pattern has disappeared!? This gives up a good clue on how to thoroughly randomize the stone material.
I'm looking for organic grit and detail in my material - right now it's cloudy and smooth so the noise get's boosted, get's finer and.....
...then get's clamped. Scaling to Clamp check-box on lets only a little of the grey noisiness to show. I turned off one of the Noise Textures to have that slot show as black.
The black in the noise texture blends in perfectly with the black of the other color. It could have been any color but I wanted a very high contrasted stone type of material.
I then swapped the color slots (little check-box) in the Marble Texture oo my veins would now contain the clamped noise. A very subtle amount shows.
Similar settings were used for the base of the material - letting just a little of the details to show through thus breaking up the orderly and predictable veining of the Marble Texture.
I'm not going to explain, in detail, the parameters of the Noise Texture - this was never the purpose of this tutorial. In the Noise procedural, the Octaves and Multipliers basically are adding finer and finer detail. The Clamp section flattens the grey range between the darks and lights - bringing out a very contrasty noise pattern. So with the clamp on, you can get bold black and white effects.....clamp off, gives a more subtle 'cloudy' effect. Both extremes are very useful in creating an organic type of material.
This is one Texture which deserves much of your attention and any time spent experimenting will be very wisely spent.
Wrapping up and general ideas
I took one material out of a number to explain my approach to using procedurals when creating stone/rock - all of the materials in the scene are based on this so there is no attempt to explain every single one.
Stacking multiple procedurals gives randomness and an organic quality to the final result. Different sizes of noise adds greatly to creating believeable textures. Hiding predictable procedural patterns with similar coloration (as done here) is a very useful trick - this one goes a long way so I think time spent experimenting will result in some very nice surprises.
Lastly, have fun...step back every now and then and don't let the numbers scare you off:-) Turn those settings and do your tests.....Brazil is a great render! It will reward your efforts.