…and why they lack photorealism
In my previous post I was reasonably pleased with how close I had come to a photorealistic render and decided that the next task would be to render some different 3D models in the same scene as had been used previously.
In doing so I have been able to confirm some of the beliefs I held when planning how to replicate the qualities of reality in 3D CGI.
In this experiment my intention was not spend time adjusting each render in pursuit of photorealism but instead to make as the minimal changes required to obtain some kind of output. In most cases this required only scaling the models to fit on top of the filing cabinet. In account of this the results are quite pleasing. This is however, not to say they are without flaw; this short experiment has allowed me to observe some other qualities of reality that are not currently present in my renders.
Looking at the 3D renders above, it appears to me that, for a number of reasons, the man-made objects (the dice and tins of spray-paint) appear more photorealistic than the organic objects (the spider, frog and snails).
A possible reason for this is that the man-made objects are far more reflective than the organic ones, and as such, the light bouncing off their surface is very much in keeping with their surroundings. It would be interesting to compare a simple render where in one image the object is very much reflective, and the other has no reflection whatsoever. According to my findings, the reflective object would appear more real.
Scale is another reason I believe the organic objects to appear computer generated; it is obvious that the spider is computer generated because it is far too big. In order to fool the brain into interpreting something as real, perhaps the scale of that ‘something’ needs to be in keeping with its real world counterpart.
It was also noticed that colour seems to play a vital role in achieving photorealism. When comparing the frog to the snails, despite the snails being cartoon-like in nature, it is they that appear more photo-realistic.
When writing about my creative journey, I was pleased to see that Weta Digital (the animation studio that created the cave-troll in The Lord of the Rings) used the colours of the surrounding environment when creating the texture for the cave-troll’s skin. The reason I found this pleasing was because I had adopted the same approach when trying to achieve photorealism in an earlier experiment where I had animated and composited a CG frog. In this experiment I utilised colours from the surrounding environment when creating the texture for the frog’s skin. When comparing the renders above, I find the cartoon snails fit into their environment better than the frog because the saturation (vibrancy) of the colours more closely match the surrounding environment. Further experimentation is required to confirm if hue and saturation aid photorealism.
Another reason I feel the snails look more real is because they are not real. Confused? Me too…
Let me try and explain; if the snails are cartoon-like in nature, they must therefore be be man-made. If they are man-made, then they don’t need to look real because in reality, there is no such thing, and therefore, our brains have fewer points of reference for comparison. Consider this; I’d bet that if I modelled a realistic snail, exactly the same as one you’d find in your garden, it would be more difficult for me to fool you into believing it was real.
It’s also possible, although this requires far more research on my part, that one of the problems with the organic objects is that no light is passing through them.
When you put your hand in front of a strong light, you can see the light pass through your hand, and as a result of the light passing through the blood in your hand, the skin turns red. It could be that the organic objects in my renders might look more real if some light was allowed to pass through them. In 3D and CGI terms, this is known as sub-surface-scattering.
The final problem that I have observed in the renders is that the 3D models are too clean and perfect. In the background photograph there are artefacts that look like they might have been created by the camera or are a direct result of resizing the background image. There is some noise and grain in the picture, some areas of the background are overexposed, and, some of the colours are bleeding into each other, whereas in the 3D objects, everything is sharp and crisp. To get a photorealistic render, my feeling is that some of these artefacts will have to be artificially created.
I know that in my previous post I said that after producing these renders I would give fresnel reflectivity more focus, however, I think the next logical step from here would be to try and prove or disprove some of the observations made above.