Bill's Reality Clinic. Reality is Chaos Part II

The 10 Principles of photoreal 3D:

1. Clutter & Chaos
2. Personality & Expectations
3. Believability
4. Surface Texture
5. Specularity
6. Dirt, Dust and Rust
7. Flaws, Scratches and Dings
8. Beveled Edges
9. Object Material Depth
10. Radiosity

Figure 1.1 Photorealism applied!

'Dwellers' is a 3D animated short film currently in production at Komodo Studio, a 3D studio in Southern California. It's about a race of cognitive thinking robotic creatures that were created by an old toy maker named Papagaio. Papagaio created the first Dweller, Gizmo, in his basement workshop. To make a short story even shorter, Papagaio built Gizmo out of discarded junk and parts he scavenged from both new and old items. The Dwellers are built from actual real-world parts. This helps to establish their photoreal credibility. This also helps determine the modeling and surfacing attributes not to mention the mechanics of motion.

Figure 1.1 shows Gizmo on Papagaio's workbench where he was created. The scene takes place at around 1AM in the basement of Papagaio’s house. He doesn't want anyone to find out about the Dwellers so he only uses a shop light to illuminate the workbench. He's just finished adding the circuit board, which is Gizmo's brain. The scene has captured the moment at which Gizmo comes to life.

Now that we've refreshed our memories, let's take a look at few more Principles of Photoreal 3D and see how they were applied to the 'Dwellers' image.

PRINCIPLE 4: SURFACE TEXTURE
All real-world objects have surface texture. Now don't confuse the term 'texture' with the reference commonly used in the 3D industry. Texture does not mean the coloration of the object. In fact, the proper term for texture is the roughness or smoothness of the object surface. It's the surface attribute that you can feel. All objects have some form of surface texture, including the smooth ones.

A common problem with the 3D objects surfacing is that they are almost always too smooth. Frequently you will see polished wood that's as smooth as glass. This just isn't realistic. The varnish will conform to the natural texture of the wood's grain, leaving very subtle variations in the varnish texture. The only way to get smooth varnish is to coat the wood with several layers and then sand the final layer smooth. This just isn't done unless you want to mortgage your house to buy a wooden desk.

You could hypothesize that the wood is an artificial veneer but then nobody would want to admit to using artificial wood in their scene. You could try sanding the wood until it is completely smooth, but this wouldn't work well either. Wood has a natural grain. To completely remove any surface texture, you would have to sand all the wood away; this just isn't a very practical solution. Keep in mind just because you can't feel a texture it doesn't mean it's not there. The texture may be too subtle to feel, but it will definitely show up in the object's specularity - particularly if the object is animated.

Another factor of varnished wood is the very subtle bump that the varnish itself creates. When the varnish dries there are very tiny air bubbles trapped under the surface, you can’t see these from any distance but if you plan to shoot a close-up of an object on a varnished table, you’ll need to add the varnish bump. Once again, you won’t really see the bump but you will see the visual impact on the specularity and reflectivity of the wood.

Take a look at Figure 1.2. This is a close-up shot of the tools on Papagaio's workbench. You can see a subtle bump texture on the wrenches against the wall. Shop tools are primarily made of chrome alloy. Chrome alloy usually has a slightly rough surface that is quite often brushed. There are also many chrome alloys that have an irregular bumpiness to their surface. This texture is essential for the tools to appear photo realistic. There is also a very subtle brushed bump map on the neck of the light. This texture is not really obvious in a still shot, but it’s very apparent when the neck is animated. It affects both the specularity and the reflection. Of course, there is a subtle texture on the wood. You have to look close, but you will see small lines between the larger grain lines. This is that tiny texture that can’t be felt but can be seen upon close inspection. While this texture isn’t necessary for distance shots it becomes an important part of close-in shots.

Figure 1.2 Real-World objects have surface texture.

I know I've been picking on wood, but it's not the only surface that requires a bump map. You'll need to add surface texture to all the photoreal objects in your scene. Particularly surfaces like plastic, rubber, metals, fabric, and even paper. Take a look at any multimedia component in your house. You'll notice the plastic has a minor roughness to its surface. If you don't incorporate that texture into the 3D rendered version of that object, it won't be photorealistic. Even smooth plastic objects have minor surface distortion that impacts their specularity. Specularity is a critical element of surface realism. It's also the 5th Principle of Photoreal 3D.

PRINCIPLE 5: SPECULARITY
Simply put, specularity is the reflection of the light source on the object’s surface. it’s a bright spot that the human eye uses to determine the surface’s shininess and hardness. Specularity is a very important aspect of photoreal 3D. it’s necessary to add specularity to mimic the real-world attributes of the surface. Without specularity, the object would appear dull, soft and flat. While this may be good for cloth it doesn’t do much for metal or plastic. Specularity and surface texture work together to simulate real-world surfaces. For example: Plastic has a rough surface texture. When specularity is applied, it adds specular highlights to the tops of the surface bumps. This does 2 things, it gives the surface bump a 3D feel and provides you with a visual reference for hardness.

let’s take a look at how specularity impacts the model photorealism in the workbench scene. Take another look at Figure 1.2. Notice how there is a soft white spot on the leading edge of each segment in the light’s neck. This subtle specular highlight is essential for the photorealism of the object. The light’s neck is made of chromed aluminium, which, like all metals, has a low specular level because it reflects light. The subtle specular highlight helps the human eye identify the surface as metal.

Just behind the lights neck you’ll see the head of a crescent wrench. you’ll notice a very subtle specular highlight on peaks of the rounded parts. The wrench has a lower specular level than the light neck because it’s a different metal surface. The wrench is made of chromed alloy, which has a lower specular level and a rough surface texture. The low specular level spreads the highlight over the surface of the object, which is then softened by the rough surface texture.

Take a look at the open-end wrench to the left of the light neck. It too is made of chrome alloy, so the specularity is spread out over the surface. The entire head of the wrench is covered in a soft specular highlight because it’s a flat surface that is parallel to the light source. This is a case where the surface texture is necessary to maintain the photorealism of the metal surface. Without a texture, the surface would be completely washed-out by the specular highlight, covering all the surface attributes. The specular highlight is broken-up by the surface texture, which helps maintain the integrity of the surface.

While specularity is important to simulate many real-world textures, there are cases where you don’t want parts of an object to be specular. For instance: You would want metal to be specular but what if it was covered in corrosion? Corrosion isn’t normally specular. Therefore you would need to make the metal specular but not the corroded areas. This is accomplished with specular image maps, which we will discuss in Part III: Photoreal Surfacing Technique. Although, there are occasions where the corrosion would be specular due to humidity or water. In these cases you would need to add specularity to the corrosion. As you can see, it’s important to identify the environmental conditions of the scene to properly apply specularity. While we’re on the subject of corrosion, let’s take a look at the 6th Principle of Photoreal 3D: Dirt, Dust and Rust.

PRINCIPLE 6: DIRT, DUST AND RUST
Dirt, dust and rust are very important aspects of an object’s surface, which are commonly referred to as Aging. There are very few clean surfaces in reality. Just look around your home or office and you’ll find most everything is covered in dust. If you have small children, it’s likely that you have stains on the carpet and handprints on the walls. I’m willing to bet that your glass tabletops have smudges and there might even be cobwebs in the ceiling corners. If you have brass, copper or silver items they are likely to be tarnished. I haven’t seen a TV yet that doesn’t have a layer of dust on the screen. Picture tubes are dust magnets! You can’t see it while the TV is on but when you turn it off, well, it's not a pretty sight.

It's not that we are lazy and don't clean our houses. It's just a fact of life, dirt is everywhere and we can't escape it -- unless we live in a plastic bubble. Yet it seems nearly every 3D scene created has somehow captured the precise moment after which it was visited by Mr. Clean. that’s a whole lot of great timing. Spotless scenes just aren’t natural. It may look great but it doesn’t look realistic. it’s important to add aging to your scenes. The level of aging depends on the scene’s background. If you are creating a factory scene you should bury everything in a layer of dirt and grime. If you are rendering a hospital operating room you can probably get away with making the scene spotless Ð well, one would hope it would be spotless. You need to consider the environment of the scene when planning your surfaces.

Let’s take a look another look at the workbench scene in Figure 1.1 and see where the aging was added. Remember when we discussed Papagaio’s personality? he’s an intelligent inventor, and that makes him neat with a tendency to get a little disorganized. His personality needs to be reflected in the scene’s surfaces. Notice how the workbench is covered in burn marks and dirt stains. Even though Papagaio is neat, it would be nearly impossible to avoid making stains on the workbench. you’ll notice they aren’t huge stains, just a little dirty. This is a reflection of Papagaio’s personality. We need to zoom in to the picture more to see some of the aging detail.

Figure 1.2 Real-World objects have surface texture. Figure 1.4 Only certain objects will be affected by the aging source. Figure 1.5 You need to follow the aging source through the scene.

Take a look at image 1.3. This is a close-up of gizmo’s oil can body. you’ll notice the top of the can is covered in rust and corrosion. This is a very important element of the scene. It justifies a great deal of the dirt in the rest of the scene. We have to assume that Papagaio has been handling Gizmo. If so, the rust and corrosion has likely rubbed off on his hands. This dirt will be transferred to the objects Papagaio handles. You can see evidence of this by looking back at figure 1.1. Here you can see that the rust and corrosion from Papagaio’s hands has rubbed off on the soldering iron grip. You can see that he handled the duct tape because there is grime on the left side and dirt on the center roll.

Let's explore the workbench scene a little more to see if we can find additional evidence of Papagaio’s grimy grasp. Take a look at Figure 1.4. Here we have a close-up of the reference book. Notice how there are dirt stains on the cover. This is another subtle sign of aging, but it’s important to ensure the scene makes sense. A spotless book on a cluttered and dirty workbench would stand out like a sore thumb. You need to sit back and examine a scene after you have staged it, to determine where and how to apply the aging.

Keeping with the idea that Papagaio is spreading the dirt with his hands, there is another object in the scene that needs some specific aging. Take a look at Figure 1.5. Here we have a close-up of the camera box. Since the camera box is open, we have to assume Papagaio handled it. Therefore it needs to have dirty fingerprints. If you look close you’ll see a couple fingerprints around the opening on the right side of the box, and a couple on the opposite side where he held the box while opening it. These may be subtle details but they add an extraordinary amount of photorealism to the scene. it’s this attention to detail that makes the scene photoreal. If you take a closer look at Figure 1.1 you’ll notice that there are grime and dirt marks on all of the tools that Papagaio has handled.

As you can see, aging is a critical aspect of a photo realistic 3D scene. Before you add the aging, take some time to explore your scene to find out what kind of aging to add, where it is coming from, and how it’s being spread. It may seem like a lot of work but it’s actually a lot of fun. How often do you get the opportunity to make a mess without having to clean it up? If you’re like me, it’s not often enough.

THAT'S ALL FOR NOW
Well, there you have it, the next three principles of photo realistic 3D images. In the next issue we'll be covering the remaining Photoreal 3D principles (7-10), which explore modeling details and lighting your scenes. Until then, take some time to experiment with these principles so you're ready when we dive into the next instalment of the Reality Clinic.

I'll see you next month.


Bill Fleming is President of Komodo Studio, a 3D studio specializing in photorealism. He is the author of the "3D Photorealism Toolkit", published by John Wiley & Sons. If you wish to contact Bill, he can be reached at bill@komodostudio.com.