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Somthing as simple as a painted wall can be hard to make look real without attention to detail. A simple material on a flat plane may very well not be good enough.

How do you achieve realistic imperfection in your work? Especially without repetition in your mapping.

Detail at the polygon level?

Displacement?

Mapping of highlight intensity?

Mapping of roughness?

What do you like to do, and why?

Let's use the wall as an example...
I think that displacement is very time consuming for large surface and long distance renderings... Unless you are rendering a chair in front of the wall and the camera is less than 3 meters from the chair, then some good textures (bump and reflection) can do the job...
On the other hand, if you want to show a stone wall, displacement is necessary... Even then, depending on your 3d app, (I use MAX) you can use some noise modifiers or some mesh subdivision so that your wall doesn't look flat...
I've done this, with good results, noise modifiers for the stone wall and then, only a normal map for the material and no displacement...
Mapping of roughness is a great way to show dirt and small changes.

I guess what it seems is there are no simple objects, and everything in an image takes time to do right.

Whenever I do something I particularly don't like it usually is due to my laziness with materials.

Nobody is more lazy than me when making materials...

It depends a lot on the look and feel of the surface itself how you should recreate it, some require a lot more work than others do. I've created a few rough materials in the past and i can think of a handful of them requiring extraordinary texturing and materials with numerous layers for exact control of reflectivity, roughness in multiple layers, numerous bumpmaps and so on..
Ofcourse the better and more detailed your models are the better your materials will look once applied to them and complex materials requires nice clean UV's to avoid stretching and scaling issues so keep that in mind.

The problem with repetition over larger surfaces could be a issue but i try to get around that problem by adding larger and smaller procedural noises, or any type of textures to break up the repetition where it stands out the most. You can cover some of it in dirt if that fits your type of mesh. Some parts can you hide in shadows and with foreground objects such as bushes and trees if it's a building you're working on.

Depending on the mesh and it's uses i sometimes handpaint all maps required, everything from bumpmaps to specular, SSS, reflectivitymaps (roughness), gloss and more. Most of the time you can get away by simply throwing on a couple of highres textures, seamless or non-seamless both work fine to give the surface some irregularities.
What really matters (i think) is the details, the stuff you can barely see.. some may say it's pointless in wasting time on such tiny details but i disagree. Everyone can make a materials with some textures in it, but not everyone can go beyond the standard and if you can do that then you can do anything. And your renders will stand out from the rest which is a nice bonus!

/ Magnus

I keep trying to think of patterns that look random when tiled together - sort of the way the 13- and 17-year locusts only compete for food every 221 years.

I guess for an ordinary house interior wall the most important thing is a small, seamless noisy pebbling that doesn't look repetitive even when heavily tiled.

-- and some sort of interruption in the highlights seems generally good.

It's hard work -- even in the real world. I takes alot of practice and a good eye to become a master of making something look both pleasing and hand made in the real world and I would expect it not to be any different in the digital realm. That said it's always best to start with a real-world example of what you are trying to achieve.

If we are simply trying to create a general purpose wall to be used on many different projects then I would look at some of these ideas:

Perlin noise is where I would start for a wall texture -- there are alot of nice Perlin noise filters on the market but my personal favorite is in Corel Painter... hidden away as the "Make Fractal Pattern" function. It not only can do most of the things you might need in a random noise generator but they are also always perfectly seamless.

As a general guideline I think of bumpmaps/normalmaps as being just that -- good for bumps. If you want more extreme texture you'll need to model it or use displacement.

A good way to set up something pretty quickly is the set a global bump or displacement for the big textures and a BSDF level bump for small textures -- have them set to different tiling so that they do not end at the same points... this will help to minimize any repeats.

That would be a good start.

Best,
Jason.

Over the past couple years I've been working at this too. Over time I have created and continually refined a couple high frequency bump map textures that work well. If you're doing products or extreme closeups, those types of bump maps are a must. Finding some super high res images are helpful to give you an idea of what type of micro detail is going on in things.

http://www.digitalartform.com/assets/vestron.jpg

As an aside, Perlin was my office mate for a few years while he was writing his doctorate on the noise function.

That's him as a TD, and me as the modeller, and yes, that Vestron logo really was rendered on a Cray (image at link above)

Now thats cool.

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