A procedural texture is a texture which is calculated at the time of rendering of an image, its principal advantage is that it does not need mapping co-ordinates which cover any surface or form in 3 dimensions.
It's principal disadvantage is that it can have periodic repetition and it especially appears more monotonous than a traditional bitmap texture.
But it remains irreplaceable in the very difficult case such as an ear object polygonal model.
With max (2.5 and 3.0) and its excellent Material Editor we can get so good results...
When I am working on a model, before it is finished, it is pleasant to have a procedural skin texture.
No concern for mapping, just apply the material and it is Practical!
In the Material Editor each texture channel (diffuses, bump, reflection...) can be a different type and standard max 3 offers so much in procedural, effect or bitmap. Digimation
one of the best creators of plug-ins for max distributes a collection of procedural textures that very interesting supplement the list opposite.
But for the moment we use what we have...
When using procedural textures it is necessary to learn how to use them, also we should not hesitate to test them one by one, by modifying the default settings.
Then we can have fun mixing them, amalgamating them to obtain others from them...
Below some examples (splat, marble, smoke, checker and cellular linen).
Of course it is not with these basic materials that we will make a little credible texture of skin. We need to mix between them.
One thing that should be known, it is that a procedural texture has a size, this works with objects on the same scale.
If we wish to apply a procedural texture to two objects modeled in different files, we will have to take care that they have the same scale ratio if not it will be necessary to modify the size of each procedural texture to make it "stick" with the scale of the model...
To start we initially will create the Diffuse part of texture, i.e. the color of the skin. We select Speckle as the type of texture for the Diffuse channel.
The first thing is to put texture on the model for scale.
To see the material we regulate the colors of texture with black and white the Defaults.
We can change the texture at the place of the colors (Maps frameworks). This is what we will do to simulate the texture of skin, pile up several procedural textures...
Before going further, we replace the black and white colors with "human" colors.
This time we use Smoke. The Smoke Procedural texture replaces the black color in or in this case the bottom slot. Opposite are the adjustments of Smoke.
It creates slightly pink spots.
Now, we use the Splat texture in the top slot.
This creates small very irregular brown spots.
Now we activate two under-textures at the same time.
We obtain a texture of skin with interesting nuances and small imperfections in the pigmentation.
Of course, such a texture is not photo-realistic but it looks good.
For better understanding of the structure of this texture, activate the Map Navigator in Materials Editor.
It is very practical to see all the complex textures with multiple under-textures.
In this representation, we see that the diffuse channel is Speckle with its two colors replaced by the textures Splat and Smoke.
Of course, we could have fun going further, Smoke itself being composed of two under-textures etc...
In the second part, we add bump for the grain of the skin and we influences the way in which the light reacts on the skin...