#59: SHADOWS & LIGHT (Vue)
(and other apps)


I often see a simple, but huge flaw in a lot of 3D rendered art, a flaw which is so easy to miss, and so rarely explained in tutorials, etc that you may not notice it!

The wall of a real life building does not have perfectly hard, straight edge. No, it is always chamfered off, by the plasterwork covering it, by damage, or the simple fact that ceramic bricks don't have razor sharp edges ;)

Because models in a 3D app are non-real geometry in 3D space, they can have PERFECT edges which are impossible in real life, just like a square drawn on a text book is "perfect" if drawn well, but in real life, even sharpened steel edges have some amount of thickness that light brilliantly sparkles off, and materials like wood and brick have far more rounded edges that scatter light in softer, broader ways.
Your brain KNOWS this, instinctively, and if it doesn't see this kind of thing, if it doesn't see grime and wear and sun bleaching etc, it knows it sees something fake.
So, you have to provide the details the mind expects to see.

CGI is about ILLUSION! :)

The edges of items tend to get worn and scractched by passing objects and creatures, faded by the sun and wind damage, or have mud, snow and other material stuck to them in passing.

For example, say you make a Poser figure of a heroic warrior, the hems of his worn trousers should be ripped, perhaps from the hard violent life you expect him to have, and be faded by wear, for he hasn't just bought them from a Gucci store! :P
Your mind knows this, and looks for it, when it doesb't see it, when it sees a fresh clean 3D model...it says "Uh uh! Fake!"

Another part of this is there should be dirt and grime and wear on nearly ALL textures in a scene. I absolutely cannot state how important plain old dirt and random difference in textures make to the reality of renders!
Doesn't take a lot to alter an object's materials to be more realistic, either.

I saw a gorgeous render, which for me, was weakened by simple fact several prominent foreground plants had all the exact same shade of colour and no "bump" on any leaf...which looked incredibly jarring, "fake", compared to the rest of the great pic.

The fault isn't often with the original model/item maker. Dirt and grime etc are very subjective to the scene, the artist's tastes etc. Plus they are a LOT of more work for the original creator to make, and it's hard enough making any 3D object in the first place.
For example, a building in the desert, you'd expect to be sun-bleached, have the lower couple of feet of walls to be sand blasted by wind and grit, etc.
But, same building in a medieval city in northern Europe you'd expect lot of moss on the walls, soot near the chimney, damp stains dripping down the walls etc.


on the LEFT side, the original model has good texturing, using varied , rough, believable-looking image for stone work
it's pretty clean, only good for a dry clean environment

on the RIGHT side, same model, I added my Layered Dirt Material over the top, making it more grimy and like you may
expect in a old European or Medieval city

And, as you can see, the model has impossibly sharp edges, you never get edges like that in real life!

Now, not every render requires such attention to detail, as everyone has their own "style" of what they like in work and what they are trying to make, plus how much time they can spend on a single artwork.
for example, if you are doing "cell shading" cartoon work you don't need this, and usually, distant objects don't need it either.
With myself, often I am "learning" with each scene I make and want to move onto the next one with what I've now learned, and don't want to spend months making one perfect picture. Plus of course, real life limits time for all of us.

Model makers often do not "chamfer" the edge of models because it adds a great deal of poylgons, which makes them use more resources, more bandwidth to download, etc.
In games, to get around this, the designers use several versions of the same model, with different "levels of Detail" (LOD), so as you approach, say, a house, the model a mile away has only a few polygons, at 200 yards it's swapped out for one with more detail, and up close one with a lot of detail.

The detail in games often comes from using "Normal Maps" to push polygons out of the model using a 2D image to keep resource useage down, as a fully detailed model with every little bit modelled and built into it would require a LOT more resources than one using a simpler model base butwith Normal Mapping which just pushes detail out based on one special image.

With recent versions of Vue, you can use displacement and Normal maps, to add details to models.
Vue Infinite and some other versions, can export the UVMap of a model, this you can then use as a basis for making or tweaking a displacement or Normal map to add features you wish.
With a bit of work, you could make the perfectly straight, unrealistic corners of a building, more rounded and believable by doing this by making your own custom Displacement or Normal maps.

Another easier way to do this, is to use a "Boolean" to cut off a roudned edge off the corner, Doesn't always work well and means you may have to texture the cut away apart.
You can take a long thin Cube in Vue, then Boolean out a Cylinder from it, leaving a curved "C" shape you can apply to a straight corner, to cut it into a more smooth, rounded shape ;)

The easiest way of all, but most difficult IMHO to get right, is simply to paint in details in postwork, in Photoshop or whatever paint application you use.
because models are non-real geometry in 3D space, they can have PERFECT edges which are impossible in real life, real edges always always have some width, which scatters light causing highlights, so knowing this, you can use highlight and shadows etc to paint the illusion of more rounded edges.

For dirt and variation in colour and bump, the simplest method is to just put a dirt material layer over the top of the existing one.
Using a random, fractal based procedural, you can make no two leaves etc look exactly the same!
Generally if you set a texture to WORLD MAPPING, this ensures the difference in position will offset the procedural between each leaf, so none look the same ;)

My free "Dirt material" does this kind of effect, though I have set it to "Object mapping" by defualt so folk could use a UVmap to drive it for precision.
Using a UV map of an object, you can make the "dirt" appear only on specific areas, again such as the hem of clothing, or the doorway of a room, deck of a ship, perhaps, or even make footsteps!

In Vue material editor, you link the UVmap greyscale image you make to the Alpha channel of the "Dirt layer", setting where there will be, and will not be, dirt using black, white and greys.

Dirt and grime and wear...aren't always dark smears, again, exposure to wind, sun and friction would leave a doorway more scratched, lighter and the raised surfaces of a door handle will have more reflection and less bump by being worn smooth.
So you need ot uderstand how real objects come to look, just like a painter does.


3D models can be specially made to have a 2D image projected onto their surface, this "UVMAP" sets out where parts of an image will go on a model.
Using this UVMap, you can make your own textures for the model, including using it to make greyscale maps to drive transparency for where dirt mapbye, or bump maps.
Vue Infinite and Xstream, and I *think* Complete can export object textures and thus UVMaps.

Bump maps are an easy way to fake surface depth on a model using 8 bit greyscale or even colour images.
problem is, it's only a "fake", so at the edges of objects you can see it's not really pushing brickwork out, for example. However, it uses less resources than Displacement or Normal Mapping.
If such details were built into the 3dD model itself, the polygon counts would be enormous, and hence, bump mapping, evne if it uses resources, is a lot LESS resources than modelling it would be.
ALso, importantly, bump, displacement and Normal mapping are not permanent, they can be changed at the user's whim!

this is like "super" bump mapping: it really does push the model's surface in or out, adding lots of detail!
However, it requires a LOT more resources than bump mapping as it can hugely increase polygon counts.
Note that like with Bump Mapping, if you only use an 8 bit image this only gives 256 possible values of grey, from black to white, and that can leave some obvious bands of differing height, like "stair steps".
16 bit images allow for many thousands of shades of grey, but require even more resources as the images have large file sizes comapred to 8 bit and not all paint applications can make them (Photoshop can however)

this is a very advanced form of bump mapping. Like displacement mapping it can push an object's surface out, but also, in varying directions and angles!
The images themselves are very peculiar blue-purple things that take some work to get used to.
Again, they can cause huge increases in resource useges, but can give incredible detail work and still use less resources than modelling the object in high detail would.

My Layered Dirt Mpa material for VUe

My tutorial on Poser clothing showing how ot add wear, grime etc and fix clothes "poking through"

Putting dirt on the bottom of rocks or walls:

Weathering 3D materials

Optimizing Poser Imports:

Making UVMapps with UVMapper:

Overlaying Materials for stians etc (old tutorial, "Layers" in more recent evrsions of Vue are btter than Mixed materials in general)

I hope you find this of use! :)

All original art, writing on this site, copyright of Steven James, "Silverblade the Enchanter" ©2012