Why an Atheist Thinks the Shroud of Turin is the Real Deal

The Element of 3D Perception

Stereopsis is not by any means the only way that our brains comprehend three-dimensional space.  Some people suffering from a misalignment of their eyes in childhood never develop stereopsis even if the problem is later corrected. And people who are blind in one eye are incapable of stereopsis. Yet such people still can perceive depth quite well. The reason is that the brain is nonetheless able to construct a sense of depth using other visual information. They are:

·         The placement of objects in front of one another: For instance, if I am looking at a person and he is holding a book in front of his chest, my brain knows that the book is closer to me than his body even if I don’t consciously realize this.

·         Geometric perspective: We all know the relative size of a tennis ball even if we don’t know the exact measurement. So if I see several tennis balls, some that are visually larger and some smaller, my brain recognizes that some are closer than others. A more common example of geometric perspective is the sense that two parallel lines going off into the distance tend to converge until they reach a point—the vanishing point.

·         Play of light. The highlights and shading on Russell’s table or on a face is the most important aspect of this. But so too are shadows cast from one object onto another object or surface. Look at the picture of Kim Dreisbach in the front of this book. Notice the white or nearly white, highlighted parts of his face. Notice the left side of his nose (your right). It is nearly black. This is shading. Now notice the very dark area just below his nose. This is a cast shadow from his nose onto the face itself.