Books on Photorealism in 3D and CGI

If you’ve been following my blog and would like to know more about creating photorealistic 3D CGI renders, you can go straight to the source with these books from Amazon:


Crafting 3D Photorealism: Lighting Workflows In 3ds Max, Mental Ray and V-Ray

Light for Visual Artists: Understanding & Using Light in Art & Design

Color and Light: A Guide for the Realist Painter

Digital Lighting and Rendering

Photorealism: You Can Do It

Digital Texturing and Painting

Elemental Magic, Volume II: The Technique of Special Effects Animation: 2 (Animation Masters Title)

The HDRI Handbook 2.0: High Dynamic Range Imaging for Photographers and CG Artists

Physically Based Rendering: From Theory To Implementation

Volumetric Lighting

In the 3D renders below I have taken a 3D image that I had previously created and tried to improve it by adopting the techniques discussed in this blog. The main focus was to improve photorealism and experiment with volumetric lighting.

When comparing the two images it’s astonishing to think that I was pleased with my original render. It goes to show just how much I’ve learnt since starting the MA.

As mentioned above, I was using this 3D image as a vehicle for experimenting with volumetric lighting. In the improved image, I have applied many of the theories already discussed in this blog, such as adding noise, depth of field, there’s now some dirt at the bottom of the wall and dust on the shelf, but the biggest difference is the addition of atmospheric dust. You can now see the visible light penetrating the right hand side of the image, it is obscuring the model’s rear leg and creating some streaks of light/shadow as it hits the top of the model’s shell.

What’s even more important in the improved render is the consideration that’s been given to the narrative. The diagonal lines, camera angle, and use of warm and cold lighting help to achieve what I had originally intended. It seems that the study of character development and cinematography have had as much impact on the improved render as the study of photorealism in 3D and CGI.

What does it take to make a 3D / CGI Object look Photorealistic?

Through my own experiments I have observed that the understanding of light is fundamental to achieving photorealism and it seems that many other 3D practitioners share this opinion.

Within the 3D environment, three aspects of light need to closely replicate their real-world counterparts:

  1. Light needs to illuminate the surface of a 3D object in a realistic way.
  2. The 3D object needs to prevent light from hitting other objects in the scene and create shadows.
  3. Light needs bounce off the 3D models in the form of reflections.

1. Light needs to illuminate the surface of a 3D object in a realistic way

HDRI

High Dynamic Range Images are a useful tool for creating photorealstic 3D renders as they create a natural light source and can also be used as an environment that appears within reflections. When using HDR Images, it’s useful to first light a scene by applying textures that have a solid colour of 50% grey to the 3D models. This allows the observer to adjust the exposure of the surrounding environment, replicating the light that was present when the HDRI was captured, before creating other textures.

Warm / Cold Lighting

When creating artificial lights, one should observe the colour temperature of those lights. Quite often, a warm (orange/yellow) light is used as a key light, and a cold (blue) light is used as a fill light. This is because our eyes are familiar with seeing the sun cast shadows whilst the blue sky casts soft light over the shadowed areas.

Colour Temperature

A 3D artist in search of photorealism should create lights that have the same colour temperature as their real world counterparts. The following is a small selection of real world lights and their colour temperature.

  • Candle flame: 1900°Kelvin
  • 100‐watt household bulb: 2865°Kelvin
  • Daylight: 5600°Kelvin

If a 3D artist in pursuit of photorealism was creating a directional light that was intended to emulate a sun, then the virtual light’s colour temperate should match that of its real world counterpart, i.e. approximately 5,600°Kelvin (depending on the time of day etc).

Volumetric Light

Any visible light within a 3D scene is created using volumetric lighting. A common use of volumetric lighting is to replicate a key light penetrating a dusty environment (More on dusty environments later).

IES Lighting

Even better than trying to match the correct colour temperature, an architectural 3D artist in search of photorealism should almost certainly make use of IES (Illuminating Engineering Society of North America) lights wherever possible. The IES have created a standard that allows manufacturers to record characteristics for the lights they make, such as colour temperature, falloff and visible light etc. These measurements are saved in a text file and made publicly available. 3D software (such as Cinema 4D) can then use these files to replicate a real world light exactly.

2. The 3D object needs to prevent light from hitting other objects in the scene and create shadows

Define Spatial Relationships

“When asking the audience to accept a scene that would otherwise strain its credibility, convincing shadow interaction can add an important piece of reality to help sell the illusion. If a production is supposed to be completely photorealistic, a single element such as a missing shadow could be all it takes to make your work look ‘wrong’ to the audience. Shadows serve the interest of adding realism and believability, even if there is no other reason for them in the composition” (Birn, )

Hard/Soft Shadows

When creating shadows, it is important to think about the source of light creating those shadows. A large light source that encompasses the entire scene would create a soft and even shadow, whereas a small distant source of light would create hard shadows. In nature, the sun casts hard shadows whereas the sky casts soft shadows.

Shadow Cookies

A cookie is used in the cinema to cast a shadow with a predefined shape. For example, if you wanted an actor to look like he was in a forest, you might cut the shapes of tree branches out of cardboard and place them between the key light and the actor. This would cast shadows that look like tress into the scene.

In 3D, if an artist is trying to composite a 3D object into a live scene, such as a photograph or video, shadow cookies cast over both the 3D model and the original scene can help to behind the two media together making it difficult for the audience to distinguish between them.

3. Light needs bounce off the 3D models in the form of reflections

Surface Texture

Although this project hasn’t gone into great depth in regard to surface textures, they are however extremely important when trying to achieve photorealism. All objects, except perhaps a black hole, have some amount of reflection, however, all have differing reflection properties. For example, a chrome lamp will have a very hard reflection, whereas a wooden picture frame will have a much softer reflection.

Fresnel

In addition to how hard or soft a reflection is, the amount of reflection on most objects will change depending on the angle you look at it. This is achieved in the 3D environment with the use of a Fresnel layer applied to the texture.

4. Other things to Consider

Colour

When creating textures for 3D models that will appear within a HDRI environment, it is helpful to use colours that match the hue and saturation of the HDR environment. Once a 3D image has been rendered, Hue and Saturation adjustments applied to the entire image help to blend the two media together.

Camera Artefacts

One problem with 3D renders is that everything produced is beautifully clean and sharp, as if it had been photographed with an extremely superior lens and sensor. In order to fool the human eye into believing something was captured with a camera, some of the unwanted by-products of cheaper lenses need to be replicated. This includes over/under exposure, chromatic aberration, noise and grain, vignetting and silvering. Stylistic choices such as depth of field should also be observed. And when shooting film or animation, other artefacts such as motion blur should also be added.

Edges

It has also been observed that in the 3D environment it is possible to create perfectly square edges which, if magnified an infinite number of times, would remain perfectly square. In the real world this is less often the case as edges tend to be worn and/or rounded. To make 3D objects appear real, hard/square edges should be avoided.

Randomness / Chaos

In addition to avoiding square edges, and perfectly clean/crisp renders, some of the random chaos of the real world should also be introduced. For example, rather than using an algorithm too create a brick wall that is perfectly straight and where every brick is exactly the same shape and size, there should be some variation. In addition to this, dirt should be added into a scene.

Dirt

When creating dirt with a photorealistc effect, you should paint dirt onto a model by hand. Burns (p229) correctly states that you should“choose dirt maps that add specific, motivated detail to your objects. Think through the story behind all of the stains and imperfections on a surface – something has to cause any dirt, scratches, or stains that you would see”. 

Dirt should only be present on the surface of models, but should also be present floating in the environment in the form of dust, steam, or similar. Volumetric lighting is a good way to achieve this.

Perception

The final thing to consider is human perception.

Scale

It’s possible, although I haven’t as yet been able to prove or disprove this theory, that scale plays an important role in creating an illusion of photorealism. We know that if we see a 60 foot gorilla on the screen, it is most likely computer generated rather than a real photograph.

Unreal

It appears that it is easier to fool the human brain into believing something is real if the brain has fewer points of reference. Take for example a human hand, creating a 3D hand that an audience believes is real is extremely difficult as it is something we spend a great deal of time looking at and accordingly we have extensive points of reference. If, on the other hand, I was to create 3D model and said it was a newly discovered creature that was found deep in the ocean, it would be easier to fool the mind into believing it was real as the brain has fewer points of reference.

That said though, it is still important to look to the real world for influence and reference when creating something that is fictional.

Improving on this Research

It’s difficult to find a way to improve upon this research, as has already been said, it appears that many other practitioners already share my view and any experiments that I have conducted myself are simply reinventing the wheel. Is it possible that all of the problems have already been overcome?

At present, I don’t feel I have explored the subject deeply enough to be able to offer any new insight that hasn’t already been discussed elsewhere.

What I propose to do now is produced some 3D renders that illustrate all of the points that I have made above. These renders will then be presented for assessment as a ‘body of work’. It is hoped that whilst creating some new renders, problems might arrise that haven’t already been tackled. However, I expect that this is more likely to happen if I approach a novel situation that other practitioners haven’t yet tried to create in 3D. This could be fun :D

To try and streamline this process, I find that although I can build 3D models, it takes me a great deal of time. In light of this, I might try and create some scenes with simple geometry, such as a piece of jewellery, a planet, or perhaps to take a scene that I have created previously and try to make it more photorealistic.

Progress Towards Learning Outcomes

In my previous post I had said that before summarising my research and producing a body of work, I must first address the learning outcomes to identify other tasks that need to be completed.

Looking at my objectives for the satisfying the learning outcomes below, I have had a new icon. The exclamation shows objectives that will not be addressed as part of this project. This was either because there is not sufficient time, or because they were found to be unnecessary.

Learning Outcome 1

“Plan, structure and develop a project proposal making reflective evaluation of the project with regard to critical contexts influencing its direction.”

Objective Achieved?
Produce a plan  
Consider key dates  
Produce a brain storm  
Product a Gantt chart  
Develop a logical approach to the project  
Plan what working methods will be adopted  
Plan what deliverables will be produced for assessment  
Plan what research materials to consult  
Prioritise which objectives are achievable within the allocated time  
Adopt reflective practice  
Reflect on findings to date as milestones are achieved  
Produce interim plans  
Reflect on creative practice to date and allow this to inform a proposal  
Write a proposal that includes all of these points  
Produce a learning contract  
Refer to the plans (plan, Gantt chart, proposal, brain storm, contract etc) at regular intervals to ensure the project remains focussed and learning outcomes are being satisfied within the given timeframe.  
Negotiate the proposal  

Learning Outcome 2

“Demonstrate informed personal insight and creative imagination through critical analysis of studio practice using appropriate media, materials, techniques and process.”

Objective Achieved?
Conduct my own experiments  
Make observations  
Observe how light acts in the real world  
Develop the above as primary modes of practice in order to facilitate the development of personal insight  
Study the mechanisms and biology that allow the human brain to interpret instructions received from the eye  exclamation
Study photography and how a digital image is captured  exclamation
Produce 3D CGI renders and compare them to photographs  
Reflect on own practice  
Evaluate studio work  
Conduct a survey  exclamation
Trial and Error  
Compare results of own findings to research done by other practitioners  
Attempt to further this research and innovate new research  
Ensure the modes of study are appropriate  
Demonstrate personal insight by sharing own working methods in the public domain  

Learning Outcome 3

“Apply and justify research methods to investigate new directions, concepts and problems and elements of risk in specialist practice.”

Objective Achieved?
Perform research in many areas, as has been identified in this brain storm.  exclamation
Attend workshops  
Justify which research materials will be consulted and when  
Promote or seek input from other practitioners  
Ensure research helps to give the project a new direction  
Ensure research helps the projects to tackle new concepts and problems  
Ensure the research carries an element of risk  
Compare results of own findings to research done by other practitioners  
Attempt to further this research and innovate new research  

Outcome

Looking at my progress to date I can see that I now need to summarise my research, plan how I can further this research, and produce a body of work that demonstrates the results.

Another Progress Update

Looking at the Gantt Chart below, it’s pleasing to see that I haven’t fallen too far behind following the long break.

Progress Update

Progress Update

Although one can see that I do need to finish summarising my research and producing a body of work, my poster presentation has already been prepared so this will free up time for getting back on track. Although before completing these two tasks, I must first address the learning outcomes to see if this identifies other tasks that need to be completed.

Been gone too long

Wow! It’s been one month and a day since my last post! Have I really been ill that long? Well, not entirely, I did spend some time over Christmas allowing my batteries to recharge, and there was the excellent New Year’s party, but for the most part, December was spent lying on the sofa, tucked up under a quilt with lots of honey, orange and other ‘natural’ remedies. Despite being bound to the sofa, on December 10th we had formative assessments.

For the formative assessment I prepared a Prezi presentation that justified, summarised and evaluated the project to date. The lecturers seemed impressed with what I had achieved but have are concerned that I’m concentrating too much on the technical aspects and not enough on the creative. I felt that this was a fair comment as I had made a conscious decision to focus on the technical.

Written feedback received presented the following question: “Is it better to show limited aspects of the job completed to a very high standard rather than to achieve a lower standard across a much broad set of work?” My response to this is that neither option is better. Instead I aim achieve a very high standard across the broad set of work. In order to achieve this I feel that I need to focus on one aspect at a time rather than trying to juggle all of the different aspects at the same time. This will allow me to ensure quality and completion of each stage before moving onto another.

Now fully recovered from the bug (although my partner is spending today in the bathroom so I might not be recovered for long) I need to evaluate my progress and identify what objectives are still outstanding.

Disgusting Looking Cat

I know, I know, I’m supposed to be studying but couldn’t help jumping into Cinema 4D and having a play with Sub Surface Scattering and the new sculpting tools in version 14.

The sculpting tools in C4D don’t seem as comprehensive as those in Z-Brush, and I found the application crashed a lot (Although this is most likely due to overclocking). Nevertheless, the tools are extremely intuitive and perfect for creating wrinkles on the cat’s skin.

Playing with SSS and Scultping Tools

Playing with SSS and Sculpting Tools

The sub surface scattering still needs attention but it’s a start.