1 Tutorials LightWave 3D Texturing for Dummies Part 1 An Introduction to the Aspects of Real World Surfaces Qua Jan 26, 2011 2:01 am
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by Leigh van der Byl |
Hello everyone, and welcome to the all new and improved Texturing For Dummies! Some of you may have read these before, but I have since re-edited them to be totally LightWave® specific, and a little more in-depth in terms of application. Most of the images I will be using are made from the content that comes with LightWave®, so you can explore all these options as I will demonstrate. Before we go on, let me just point out that under absolutely no circumstances are you going to find any tutorials on how to make tacky chrome surfaces or light blue glass in this series. There is quite enough of that out there already. Not that I think there is anything wrong with those, it's just that those tutorials will only get you so far, and when you are suddenly faced with the challenge of texturing a photorealistic shower attachment or elephant's toenail, they are going to get you nowhere. What I intend to do is to illustrate exactly how to observe real life surfaces and recreate them digitally. With all the frills. And that means absolutely no tiled texture maps!. Basically, I am hoping that this can be a sort of "texturing manual" for you when you need to do your texturing - so if there is anything in particular that you want to know more about, let me know, and I will include in an upcoming chapter. Luckily for us LightWave® users, we have a FANTASTIC surface editor with which to work - in my opinion, the Surface Editor in LightWave® has the greatest number of options available for us to work with, with the least amount of hassles. There are no surfaces that you cannot somehow produce with a little know-how and clever manipulation of its settings. Within LightWave®s Surface Editor, you have all the tools at your fingertips to make beautiful, believable photorealistic textures. All you have to do is know what all these options are! Well, let's begin! Observing the Aspects of Surfaces In Real Life If you wish to become a brilliant texturing artist, the first thing you are going to have to do is learn how to properly observe surfaces in the world around you. You need to look at things and, in your mind, break the surface apart into its different aspects. Look at a brick wall - study the variations in colour, notice how the light is broken up along it's surface, feel the groves, scratches and bumps on the bricks themselves as well as the grain of the cement between them. Even take note of it's temperature - I know that sounds strange, but that can become very important when you are trying make people really believe that the surface exists. People looking at your textures must be able to imagine exactly how it feels to touch, and the temperature of the surface is definitely important, But that is a detail that I will go into depth at a later stage. You need to begin looking at the world around you in terms of the aspects that you will recreate digitally. I know this may sound really bizarre, but when I am driving to work in the mornings (this usually being the only time of day that I actually see the world outside.), I often find myself looking at an old garbage can on the side of the road, and thinking "hmmmm. that can has an awesome diffusion map on it" or looking at an old council truck and thinking "what a cool specularity map that has". It is because I think like that, that when I sit down to work and am given something to texture, I can draw directly from my memory and experience, because I do know offhand what the diffusion of metal looks like, or how to do really great rusty streaks on the side of a truck. Make an effort to break up things you see into Colour, Diffuse, Luminosity, Specularity, Glossiness, Reflection, Transparency and Refraction, Translucency and Bump aspects. Some surface areas also include Displacement, which is basically a Bump map that actually alters the geometry, but because it is then, technically, a geometric property, I will not deal with it in too much detail, as it doesn't really affect the other surface attributes as such. Observe how these different aspects interact with each other - for instance, very reflective transparent glass, isn't very reflective and is less transparent where it is scratched and where it has been dulled (by been handled or by being wiped by a dirty cloth). Now, in order to begin observing all these aspects correctly, you need to have a very good understanding of what each of these are. The Different Aspects Of Real World Surfaces Of course fully explaining every one of these properties in great depth would take too much time right now, so I am going to give a very brief explanation of each of them now, and then later on I will do a separate workshop dealing with each of them individually. Pictured below is the star of the show for today - I pried this gorgeous little skull out of the content that comes with LightWave® to demonstrate how the different parts of texturing work, and how each different aspect affects its surface. Let's call him Frank. Now, although Frank looks pretty fantastic already, I think that perhaps he should have a makeover, just for the fun of it. Let's see what we can do with him.. Colour The first aspect of texturing! Well, I guess this one is pretty self-explanatory. All objects have colour. Although it is probably the most basic of the surface attributes that you will have to make when texturing something, it is by no means an easy one to produce. Nothing in real life has a constant perfect colour. Any object has a colour which is uneven in places, even if only slightly. The colour map is usually the best one to start off with, when beginning to texture a new object, as it will give you an excellent starting point for the feel of the object. Be sure to add in loads of details for added realism - things like faded areas, scratches, smudges, blemishes, weathered marks - anything that makes it look like it exists in this world. Colour maps are generally the only image maps that you will make that contain any actual colour, as the other surface properties are best created in shades of grey. Okay, so lets add some colour variations to Frank and see what happens... Firstly, I've set all the other surface properties to 0%, so all you are seeing below is the raw colour applied to the object. As you can see, the colour is very important to place the details that you need on the surface. These are just very simple examples of colour maps for surfaces - for really realistic recreations of things, you need to study the object that you are making very closely in order to ensure that all the necessary details are included. Reference material when texturing things is absolutely essential - always have loads of reference pictures of the the kind of surface you are trying to make, as well as actual physical examples, if possible. Obviously, because there are only colour properties and nothing else assigned to Frank at the moment, he is looking a little flat. So let's explore some more options for getting him looking a little more interesting... Luminosity This attribute determines whether or not an object has any self-illumination properties, and how strong they are. This is only used for things like florescent lights, light bulbs, LED displays, electronic billboards, lava, molten metal, and so on. Below, Frank seems to have transformed briefly into a volcanic landscape! A luminosity map works best in conjunction with radiosity, so that the luminous value can become translated during the render process as a source of light, and will thus illuminate objects around it slightly. Bear in mind that your settings have to be rather high for this effect to work best. For added effect, it's often nice to add an appropriate amount of glow to the surface. You can enter in a glow value in the Glow Intensity box under the Advanced tab in the surface editor. The Glow Intensity option in the Surface Editor Note that in order for your object to render with the glow you have assigned to it, you need to enable it in Image Processing. You can do that in Layout by going to Scene>Effects>Image Processing, and ticking the Enable Glow option. You can also assign your overall glow intensity, as well as set the glow radius (its size) in pixels. You need to activate the Enable Glow option to render your surface with a glow The glow option is cool for adding a halo around a lightbulb, or a faint shimmer around a magical crystal, and other things like that. For more dramatic effects, such as the haze of light from a streaming river of lava, I would suggest actually using volumetric lighting, as the glow will probably not be sufficient. Diffuse One of many great things about LightWave®s Surface Editor - we have the option of real diffusion. Firstly, let me dispel a common misconception - diffusion is not colour! Diffusion is the attribute of an object's surface that scatters light. It determines the actual amount of light that is reflected by the surface. In essence, it determines how much of the surface's colour we'll see. By diffusing an object, you limit the amount of colour that is reflected back by the light. This is completely different to simply darkening the surface of the object itself. If you were to darken the actual image used as a colour map, you would see only see a change in colour, but not a sense of colour depth. Colour depth is created by scattering light across an object's surface. Take a look at human skin and you'll notice that it has a density. The colour isn't a simple continuous shade but rather many similar shades, created by scattered light. This quality can not be made by a colour map alone, as a colour map cannot give a surface the richness that a diffuse map can. Obviously, having said that, Diffuse and Colour go hand in hand. Diffusion also works very closely in conjunction with Reflection, which I will discuss in a moment. Something to bear in mind when using diffusion is that you need to lighten your colour maps in order to compensate for the amount of darkening that the diffusion will cause. For instance, if your surface has a diffuse amount of 80%, you should make all your colour maps 20% lighter than they would ordinarily appear to be, so that when the surface becomes diffused, these tones do not become desaturated or too dark. Using diffusion correctly ensures that your surface does not become oversaturated when it is illuminated by a light source. Surfaces that have 100% diffusion tend to have large, unsightly oversaturated hotspots where the light hits them - lowering the diffuse amount appropriately prevents this from happening. I will be going into great depth about Diffusion in Part 3 of this series. Specularity And Glossiness It is a shame that Specularity, an extremely important aspect of a surface, is all too often overlooked. In fact, I would say that Colour and Specularity are the two most useful basic surface attributes in determing the initial look and feel of your surface. Below you can see that Frank has now got a bit of specularity (as well as some bump, to help define the surface, and thus enhance the specularity a little) applied to him: The specularity of an object determines how shiny it is and how light is broken up by it's surface. Now, keeping in mind what I said earlier about being aware of how people and weather interact with and affect a surface, you make use of a specular image to show how the world has "made it's mark" on the object, so to speak. Things like smudges from a cloth, fingerprints, wetness, polishing, etc will all play a part in determining what goes into the main specular image. Specularity works most closely with three other surface properties - Glossiness, Bump and Reflection. Specularity in conjunction with Glossiness determines how spread out or how tight an area the light's "hotspot" becomes when it come into contact with the surface. An object with only a small difference between the specularity amount and the glossiness amount have a very small "hotspot", therefore they appear plastic-like; whereas an object with a large difference between the two will spread the light out over a much wider area, therefore appearing more dull, like metal (except chrome-plated metal, of course). The moment you add any specular amount to a surface, the Glossiness option becomes activated, and you adjust this setting in order to get the right balance of shininess. Bump works hand in hand with specularity in that generally parts of an object which protrude more become more worn. And depending on what the surface is, that will either increase or decrease the specularity - wood, for instance, generally becomes shinier when it is rubbed a lot, whereas metal can become duller. Another way in which bump and specularity work together is in the case of scratches along a surface - a scratch will tend to gather grime and dust, and will therefore become very dull after a while. A quick way of ensuring that your specularity interacts nicely with the bump map, is by placing a gradient into your specularity channel that gets its input from the bump map, as shown below. You can use a gradient set to Bump as its Intput Parameter to control the specularity according to the height of the bump map The interaction between reflection and specularity is pretty obvious - where a reflective object has been, for instance, touched by a person, oil from the fingertips gets left behind, and makes the surface appear less reflective in that area. Another example would be if you had to texture a car's front windscreen, where it is a cold night and the driver has wiped a cloth along the glass to clear the mist on it, the cloth leaves lines in the direction it has been pulled across the surface - those streaks will make the surface appear a lot less reflective than parts that weren't touched by the cloth. It is probably safe to say that there exists no object in this world that is 100% reflective all over it's surface, because sooner or later, someone or something is going to touch it and affect it's specularity, thereby affecting it's reflection. There is a wide debate, however, between the use of reflection and specularity. A lot of people prefer to not use specularity, and prefer instead to solely rely on reflection to make their surfaces shine. I will explore this debate further in Part 4 of this series. You get two common kinds of specularity - normal specularity, and anistropic specularity. Normal is just plain straight specularity, whereas anistropic specularity is used for surfaces which has extremely tiny bumps along it's surface. You can implement Anisotropic reflections by using LightWave®s BRDF shader, but I will get more into detail about that when I deal with specularity at a later stage, in Part 4 of this series. Reflection Another pretty self explanatory property, reflection determines how reflective an object is and in what areas it is reflective. Below, Frank has become chrome plated... As previously mentioned in the paragraph on specularity, the reflection map should vary along the surface according to how it has been interacted with. This attribute is sadly often overused - a huge giveaway that an object is CG is often due to the fact that the texture artist has made it too reflective. That is not to say that reflectivity is not a common property - in fact, most things which are in any way shiny, are slightly reflective too. Although reflectivity is not to be confused with the effect that radiosity has on objects, where the surface of one object can pick up small traces of the colour surrounding it due to bounced light. You should attempt to create this effect with reflection, as your surfaces will just end up looking wrong. The kind of reflection that an object has also differs greatly - a mirror, for instance, produces a perfect reflection where it is clean, whereas steel, plastic, scratched Perspex, most liquids, etc, have blurred reflections. LightWave® 7.0 (and onwards) has a blur option for reflection - use it. All too often, you see horrible renders of perfectly reflective kettles and such, when the reflection should have been blurred. When working with reflection, something very important to bear in mind is it's relationship with Diffusion. As a general rule of thumb, the more reflective and object is, the lower its diffusion. This is because the more an object reflects, the less of it's own colour we can see. However, I will discuss this relationship in greater depth at a in Part 3 and Part 4 of this series Transparency and Refraction Transparency is not Opacity. It is, in fact, the opposite. Transparency determines how "see-through" an object is (whereas Opacity determines how opaque it is. An object which is 0% percent opaque will generally disappear out of a scene, whereas an object with 100% transparency will just be completely see-through, yet still visible). Obviously, things like glass, Perspex, liquids, crystal, etc have varying degrees of transparency. Transparency is also affected quite a bit by the specularity of an object - especially in the case of oily fingerprints left on a surface - obviously these areas are not going to be as transparent as the surrounding areas that have not been touched. Transparency has a special relationship with Reflection, called the Fresnel Effect. This effect is basically the variation of transparency according to the angle at which you view it. An example of this is if you see a lake from a far off distance, it appears very reflective, yet the closer to come to it, the more transparent it appears. This effect of becoming less reflective and more transparent increases as the angle at which you see it increases. You can implement this effect by using LightWave®s Fresnel Shader, or by using opposing gradients in your Reflection and Transparency channels. I will discuss the Fresnel Effect in the upcoming chapter on Reflection. Most substances which are transparent, refract light. Refraction is the bending of light through transparent bodies. This causes the effect of, for instance, if you have a scene with a glass of water in it, when you look at objects through the glass of water the objects you see are warped. Different substances have different refraction amounts, and a table of these amounts can be obtained almost anywhere - however, to make things easy, you will find a handy Index Table inside your LightWave® manual. The higher the refraction amount, the more light is bent as it travels through it. Refraction amounts in reality do not exceed 2.0. In the picture above, Frank has a refraction index of 1.6 - as you can see, this results in a rather drastic distortion of the surface behind him. Translucency Translucency is the ability for an object to be backlit without being transparent. Take for instance, a curtain - when a light is shone through it, you can see things moving behind it, even though it is not transparent. In reality, just about everything, with the exception of metal and wood, has some degree of translucency. This property can be extremely useful for skin, in particular, so that if a bright light is shone onto it, you can catch a glimpse of the veins which run just below the surface. In the picture above, I have placed a point light with a short falloff inside Franks head, which is revealing the translucency map of veins that I have placed on him. As you can see, where the light shines through, the veins are visible because they are getting in the way of the beams of light. Translucency works best when combined with a calculation called Sub Surface Scattering, which is a property that basically allows light to enter the surface of an object, bounce around inside the surface, and then leave it at a different angle to that in which it entered. Translucency and Sub Surface Scattering are extremely important, especially for surfaces such as skin and fabric, where they should always be used. LightWave®, unfortunately, does not yet have built-in Sub Surface Scattering, but there are a number of plugins available that you can use in the meantime. It's probably safe to say that just about everything in this world is translucent to some degree, so it's a pretty important thing to keep in mind. Bump The most commonly-used attribute next to Colour. Everyone knows what a bump map is. Although, I must stress that a bump map should never be used as a compromise for necessary geometry. Bump maps should only be used for minor things like scratches, small dents, grooves, small carvings, minor variations in relief, and grain. Never ever use a bump to create something that should actually be modelled. The reason for this is that as soon as you get close to a bump map, it becomes obvious that the objects surface relief is actually flat. An alternative to bump mapping is displacement mapping - displacement using textures is similar to bump mapping, except it actually deforms the objects surface according to its settings. To use displacement in LightWave®, you can make go to your Object Settings in Layout, and activate the Displacement option under Deformations tab (see Figure B). Activating the Bump Displacement option in your object properties A Note On Making Your Own Texture Maps Something that is extremely important when making your own texture image maps, is the size of the actual image you make. In order to determine what size you should make it, you need to know what the final rendered frame size of the animation is going to be. Once you know what the final size is, then you can work out the size of your texture map as follows: Take the maximum width that the texture map can appear on the screen (in pixels) and multiply it by two. Use this pixel size as the size of your image map, if you want to ensure that your textures do not become blurry or pixellated when viewed up close. For example, the most common frame size when rendering for television is 720 pixels X 576 pixels (PAL D1), so if you were to make a texture image for an object that will be viewed right up close in the frame, then the width of your texture map should not be less than 1440 pixels. I personally usually work with square images, as I almost always work with UV Unwrapping, so my images are generally at least 1440 x 1440 pixels. It's usually safe to leave the image at 72 Dpi, as this is the resolution that monitors and televisions display at. Of course, the drawback to this is that these kinds of file sizes for image maps do slow down the rendering process quite a bit, but on the other hand, you know they will hold close-up. So if you have a job that is going to end up on IMAX, you had better make sure your computer can handle 4000 x 4000 pixel images.. Another important thing to know and understand is how to make greyscale textures correctly. As you know, greyscale images are the best method of making maps for all the properties apart from colour. In order to decide what shades of grey to use, you need to first decide on an overall percentage value for the overall channel - for instance, if you are wanting to make your specularity map, and your overall amount is 12%, then start off by making your image 12% grey. You can do this in Adobe Photoshop® by opening the Colour palette and entering in a value of 12% into the B radio button where is says HSB, above the RGB options. This ensures that once you load your image map into the specularity slot, your map will not alter your overall amount except for the areas that you have worked more detail into. Using this method ensures that nothing unpredictable will happen, and gives you this greatest control over maintaining overall amounts remain the same. That pretty much wraps up Part 1 of this series! I hope that have learnt something, and that you feel more confident about approaching these different options in the Surface Editor in future. Obviously, this was only a very brief introduction to each of these attributes, but it is only an introduction, after all. Stay tuned for more chapters in this series, when we will explore each of these in great depth, and I will be demonstrating how to make the most of them, and how to create great textures for each... By Leigh van der Byl [Tens de ter uma conta e sessão iniciada para poderes visualizar este link] . |