I guess you could flag this as biology and physics both at the same time, but it only let me pick one, so I went with other. I understand that parallax is how the landscape moves in the background, but I’m unable to explain it to someone else.
In: Other
Hold your thumb out in front of you and look at it with one eye closed. Now close that eye and open the other one. How your thumb appears to jump back and forth in your view is parallax. Its an exercise in apparent perspective.
Parallax describes the apparent movement of something when observed from two points not on a straight line with the object. Imagine if you were to look at an object which is a foot away, and then you moved a foot in any direction but directly towards or away from the object. It would move a fair amount in your vision, right? But if you repeated that same trial with something which was a mile away, it wouldn’t appear to move very much at all. That movement as your perspective changes is parallax. (Note that if you moved directly towards or away from it, it wouldn’t appear to move at all).
The reason it exists is because you effectively create a triangle with the object you are looking at and the two points you observe it from. The closer the object is to the points, the larger the angle created in the triangle at the object you are looking at it – meaning it appears to move more. We can use the apparent difference in where an object appears when observed from two points to calculate how far it is, so long as we know the distance between the two points. This was useful for making maps before satellites existed, and it’s still useful for calculating how far away nearby stars are.
Your two eyes looking at an object form a triangle. The lines connecting each eye with the object form 2 sides of the triangle, and the angle between them is the parallax angle (twice the parallax angle to be accurate).
The lines extended to infinity define the background each eye sees.
The closer the object to your eyes, the larger the angle, the more distinct the background seen by each eye.
Faraway objects create a small parallax angle, and background is largely same from both eyes.
Over our lifetime, the brain creates empirical relationships between observed parallax and perceived distance, which is how you can guess the distance of a certain object from you by subconsciously backtracking how much parallax you’re observing.
Parallax is how one object can appear to be in two different positions when viewed from two different lenses, generally your eyes.
If you look at an object using your left eye (with your right eye closed), then look at the same object but switch which eye is viewing and which is covered the background behind the object will appear to shift even though neither have moved.
This affect also happens when you, the viewer change position and look at the same general view. Objects that are closer to you will appear to move more than objects which are further away.
Imagine putting a post in the ground 6 feet in front of you, so that you form a straight line between yourself, the post, and a distant mountain. If you move 3 feet to the right, the post will appear on the left side of mountain. If you move 3 feet back to the middle, then 3 feet to the left, the post will appear on the right side of the mountain. The post seems to be moving horizontally significantly, while the mountain appears not to move, or move only a minuscule distance.
You can fake 3D effects by layering different images one on top of the other and shifting them at different rates of speed, so long as you make sure the further the layer is back, the less you move it.
A good way to see the difference is to compare the original Super Mario Bros game for NES with the remake version in Super Mario Allstars. The original game featured fixed backgrounds the moved at the same speed as the foreground. The remake added a mid layer and a far layer behind the foreground which moved at 2 different speeds, generating a simple 3-d effect.
.
Latest Answers