Computer Vision (3)

One statement that I usually get to hear from people is: “I understand the significance of depth on our perception of the surrounding, but a photograph as you said is a 2D image and my brain still manages to extract all the information from it. So should robotic vision depend so much on depth? Why can’t we do away with it? Also take movies for example, which are a sequence of 2D images. You can actually feel depth in them, don’t you? I still don’t understand why we need 3D?”

We understand a 2D image completely because of our previous knowledge and not necessarily due to the image processing happening in our brain. Previous knowledge does not mean that we should have seen the exact image before, it means that we are aware of the context and content. Like in image processing, we don’t understand the image after segmentation; both of them go hand in hand in our brain. What kind of segmentation our brain uses is still not very clear, but I can demonstrate how knowledge rules over the kind of segmentation that we can perform on an image. Look at the image below for example. What do you think the image contains? I am sure, 100% of the people would say “a man and a woman”. You are totally wrong; the artist had actually drawn jumping dolphins on a pot! Now that you know the content of the image (knowledge) you can easily extract the dolphins out.

You feel the perception of 3D in a cinema due to motion; a cinema is a motion picture! Motion can be obtained in two ways; one by keeping the camera static and having motion in the subject or bring about motion in the camera itself, irrespective of the subject. What our brain does using two eyes could have been done with a single eye, by oscillating it left and right to get the two images that it needs. The only difference would be that the images would not be from the same instance of time. From the time we start learning about our surroundings it is 3D vision that helps us segment the objects around us and put it in our database. Once we have gained sufficient knowledge about our surrounding we do not need 3D to perceive them, which is why we understand a 2D photograph without any problems.

I will be dealing with these topics in detail later on under illusion and 3D perception through motion. I have only been introducing you, to all of them now.