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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.
I’d hoped to gain more insight from reading Jeremy Burns chapter on Decals and Dirt, but found that I had already been using what he refers to as Decals in my projects. In the example robot image below, I had already applied decals (stickers) to my robot, however, what I hadn’t done was added dirt.
In this example I’ve probably gone a little over the top with the dirt but it helps to illustrate the point I’m making.
When I showed the animated version of this robot to a fellow artist, he immediately noticed the lack of movement in the robot’s hands and how clean the robot looked in comparison to the background. Although the film noise/grain and motion blur that had been added were helping to blend the two media together, it seemed the texture on the surface of the robot’s skin, was too clean and shiny to begin with.
In the example above, I’ve used Ambient Occlusion (a tool for finding edges between two surfaces and is often used to emphasize shadows) to create the dirt which in my opinion is a inaccurate way to achieve the effect. 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”.
In the example above, dust would have fallen and settled onto the robot from above, this would mean that the robot’s shoulders, head, bridge of it’s nose and chest would probably have accumulated the most dust. Similarly, water dripping from the ceiling would have created vertical streaks running down the robot’s body.
Painting in these extra details will require considerable time but it’s this attention to details that will eventually sell the illusion of photorealism.
In my previous post I demonstrated that Replicating Digital Imaging Artifacts helped to achieve photorealism.
To further this research I have been experimenting with replicating artifacts found in digital film such as grain, and motion blur and adding them to 3D animations.
The examples below show a single frame from an animation, one with the added artifacts and one without.
When looking at a single frame, the motion blur effect seems out of place, but when watching the animation and the motion blur of the original camera movement becomes apparent, it is clear that the replicated blur helps to create the illusion of realism. In contrast, in the animation without the added motion blur, the sharpness of the cg elements stand out from the noisy, blurred background and begin to hinder the illusion of realism.
As well as motion blur, other artifacts have been added according to previous findings such as chromatic aberration, vignetting, and noise.
The affect of sound will be discussed in a future post.
Throughout this process of trying to emulate reality I have speculated that it is not the real world that should be emulated, but realism as found in a photograph. To this end I have attempted to replicate some of the artifacts that occur in digital photography in order to improve my previous best attempt at replicating reality.
The Image ‘Without Post-Processing‘ shows the previous attempt at achieving photorealism.
In the image ‘Camera Artefacts‘ I have added some chromatic aberration (The red fringe on the edge of the balls), I have scaled the image up and down, compressed it and decompressed it, and used run length encoding to degrade the quality of the image, and have also added some noise. All of these effects would occur naturally when working with digital photographs.
In addition to this I have also desaturated the image and adjusted the colour balance to make the highlights a little more blue. The benefits of this are that all of these changes affect the entire image, not just the 3D elements. As both the background and the 3D elements have been affected by the same processing, it becomes more difficult for the eye to distinguish between the two forms of media.
For reference, the original photograph has been included also.
Whilst there is not as much noise or chromatic aberration in the reference image, when comparing the two artificial images, it is the image with the added artifacts that is most convincing.
In my previous post I had noted that fresnel reflectivity was producing the most photorealstic results, however, before dissmissing other reflection types, I decided to conduct a further experiment.
In the renders below, the first image (top-left) shows three spheres rendered without any texture applied to them. It was interesting to note here that the spheres are very dark. When trying to achieve photorealism in this image previously I had noted that the spheres seem quite dark. Without any texture, it makes it far easier to see how dark they are. In the future this will prove useful when making adjustments to achieve correct exposure from the surrounding equirectangular panoramic HDRI sky dome.
In the second image (top-centre), adding some colour to the speheres supports the illusion of photorealism. This is perhaps because white is more reflective than black and some of the colours of the surrounding environment is seen to be reflected in the spheres. For example, there is a green tint in the bottom of the spheres where the surface of the filing cabinet is being reflected onto them.
In the third image (top-right), the spheres are 100% reflective. Contrary to my previous observations, this image does not appear as photorealistic as the white spheres. I believe this partly to be due to the reflection being too clean; in reality there might be smudges of grease, dirt and the like, you’d also be able to see a camera or similar in the reflection. In addition to this, the reflection in the coloured spheres is almost like a fresnel reflection which could account to its being more photorealistic.
However, this does confirm that fresnel reflectivity is superior, however, fresnel reflectivity alone is still flawed, as can be seen in the following image (bottom-left). In the image titled 100% Fresnel, the centre of the spheres has no reflection whatsoever. This is not a realistic effect.
It seems then, that it is a combination of all of these things that will have the greatest effect when trying to achieve photorealism in 3D renders, as can be seen in the final render.
In an earlier post I predicted that reflective objects would appear more photorealistic than non-reflective objects. Having conducted a short experiment, I can confirm that this is true.
Looking at the three renders below, it is the cube without any reflection that appears to have the least photorealism, the cube that is completely reflective is closer to photorealism, and the final cube, with fresnel reflectivity, is an improvement on them both.
This shows that reflection does have a vital part to play in achieving photorealism, but further experiments are required to identify if fresnel reflectivity is the key.