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


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.


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


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.


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.


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.


The final thing to consider is human perception.


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.


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 😀

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.

Shadow Cookies

In his book (Digital) Lighting & Rendering, Jeremy Birn (2000, p63) states that “shadows serve a practical purpose in most scenes by showing the spatial relationship between objects. They show where an object is planted on the ground or how far an object is located above the ground”. Without shadows it is difficult to interpret the spatial relationship between objects in a scene. Looking at the image below, it is difficult to tell if the balls are floating in space or resting on the cabinet.

First Render

First Render

Birn (p66) goes on to say that “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”.

In the image below, although the lighting on the spider matches the rest of the scene, the absence of a shadow being cast onto the ground spoils the illusion.

Without Shadow

Without Shadow

In the following image, the ground shadow below the spider helps cement the relationship between the environment and the 3D model.

With Shadow

With Shadow

The practice of adding a shadow to support the illusion is something I had commented on previously through my own observations, however, something that I hadn’t previously considered but is demonstrated by Birn is the use of casting shadows by objects not visible on-screen. In the following image, a cookie has been created to cast shadows over both the spider and the environment thus cementing the real and virtual elements together even further.

With Cookie Shadow

With Cookie Shadow

Research Plan

I order to compile a research plan the brainstorm that was generated at the start of this project was consulted in order to identify areas of research that would support this project. Regrettably, the course deadlines dictate that only avenues of research are priorities in order of importance and many of the subjects will not be included in research.

I’d said earlier in my observations that I needed to study Sub Surface Scattering but have not as yet achieved this. As I have begun modelling the cats for my animation, sub surface scattering will be an important part of making them look real. In addition to this, I have no experience of using specular maps but currently believe that specular maps will play an important role in achieving realism in the primary characters of the animation. In account of this, Sub Surface Scattering and Specular Maps will be researched.

I have already spent time exploring reflections but have not as yet begun experimenting with transparencies and refraction. Unfortunately, as the animated project doesn’t immediately require transparency, this area of study is not a priority.

In my original hypothesis, It’s suggest that the study of digital photography might hold the key to achieving realism. However, many of the artefacts that are created as a by-product of digital imaging have already been generated so the study of photography is not a priority either. It would be useful to explore depth of field and how a shallow depth of field can be replicated in the 3D environment, although this will only occur once the primary topics of research have been exhausted.

One area of priority should be Gamma, Linear Workflow and Colour Profiles as they enable better support for HDR Imaging and colour replication. I have studied these areas previously in my MA, but don’t feel that I have as yet achieved sufficient understanding to effectively incorporate these methods into my practice.

The primary goal of the research should be studying what has been done by other practitioners in order to achieve photorealism so that I can compare their findings to my own and attempt to improve upon what has already been discovered.

I will need to give some attention to finding some focussed research materials that will most likely be in the form of online articles, blogs, portfolios and videos, as well as books and magazines.

One artist in particular who seems to have an excellent grasp of photorealism is Alex Roman. His work will be consulted in order to identify areas of good practice.