# Thread: Isn't 3D really 4D? Need help with this!

1. ## Isn't 3D really 4D? Need help with this!

This is a topic I have struggled with for many years and can't find any interesting discussion on it.

Zero D = finite point of focus
1D = a line representing 1 axis
2D = the form of a shape along 2 axis x and y principle
3D = a depth or plane added (ie. the depth and field percieved in a photograph)
4D = depth and perspective when movement is added (ie. when the head is moved side-to-side the images react with one another with the closest objects moving against a more stationary background)

* () brackets are my own interpretation of each.

The problem for me is I have been under the impression that 2D would include a visual like an old atari game with no depth of field and adding that depth like the newer consoles added a 3rd dimension. However if one tries to move or swerve their head it makes no difference in the field of vision. So, if you add that extra dimension aren't you really adding a fourth dimension?

While my curiosity doesn't come from gaming (not into video games), it comes from being an artist who is interested in perspective.

Any and all input would be greatly appreciated even if it goes beyond 4D.

2. no, the 3 dimensions allow for movement within them. Movement along the 3 axis' only proves that the axis are present, the movement does not imply an extra dimension.

3. Originally Posted by KJanon
no, the 3 dimensions allow for movement within them. Movement along the 3 axis' only proves that the axis are present, the movement does not imply an extra dimension.
Thank you. That helps clear it up a bit.

How does 2D get left at 2 axis when there is a percievable depth to it? Or is it based on a law of science?

I guess this is where my understanding gets muddled.

4. Originally Posted by ilostthesheriff
Thank you. That helps clear it up a bit.

How does 2D get left at 2 axis when there is a percievable depth to it? Or is it based on a law of science?

I guess this is where my understanding gets muddled.
it's best to think as dimensions as a sting. You can only move along 1 axis on the string, forwards and backwards. Therefore the path along the string is 1-dimensional.

However, that string can be within a 3-dimensional space. That string may not be straight, and it's space may use all 3 of the dimensions it is contained in, but the path along the string is considered 1-dimensional (for instance, to travel from 1 place on the string to another, you MUST pass through a point between them each time you do this, you cannot use an extra dimension to avoid this).

We often view 2D objects in 3D space. Whilst a piece of paper is 3D, and has volume, we're only interested in it's flat face, so the third dimension is negligible is say, a drawing.

5. The mathematical principal of 4 dimensions is that the points of perspective physically change when movements are made... It's quite a bit different from 3D...

One way you can look at the 4th dimension is by taking a 3-Dimensional Cube, and then extending it outwards into the 6 separate planes, that being (+X, -X, +Y, -Y, +Z, -Z) It's a bit confusing to visually show, however it can be done. Here you can see an image of what I am referring to.

http://boonce.org/up/2495_Untitled-1.png

As you can see in this image, the 4th dimension has a perspectively altered cube on each of it's sides. You can move these cubes inward and then one of the outer cubes (the one you move to the center) get's changed into a "3-Dimensional Cube" while the one in the center is changing it's perspective, and the one opposite what has been moved is physically flipped in perspective (assuming a perfect 180 degree rotation inwards)

After the 4th dimension this principal continues to take place...

That is that the 5th dimension (visually) is similar to a 4th dimensional cube, then extended among all of it's axes. It begins to get substantially more difficult to represent each dimension after this.

I hope this helped a little bit.

Edit: Animation, substantially better than my drawing http://www.moillusions.com/2006/06/4...animation.html

6. KJanon and Lobie: Thank you. Gifted explanations! My mind is blown and will have to research this further. Especially into how this science plays into the human perspective on sight versus intuition of space especially for the blind. Amazing new topic for me!

conceptual vs. visual.

7. 4th and 5th dimentions? This is starting to remind me of Alevel maths! Surely the only dimentions that are aplicable are the x y and z this is all that is needed to describe any object in space the only other variable is time, commonly referred to as the 4th dimention. This is all that is needed isn't it?

8. Originally Posted by Lilsteve
4th and 5th dimentions? This is starting to remind me of Alevel maths! Surely the only dimentions that are aplicable are the x y and z this is all that is needed to describe any object in space the only other variable is time, commonly referred to as the 4th dimention. This is all that is needed isn't it?
Absolutely not! In fact, up to the 10th dimension are useful in mathematics. Why? Hmm, I don't think I'm the one to answer this, but you do deal with Multi-dimensional basis in Linear Algebra, and I know it is used in many other areas of math.

Even in all of the CG-Animated movies are in 4th dimension, granted the 4th dimension isn't a physical dimension as it is in mathematics.

Imagining the Tenth Dimension - A Book by Rob Bryanton This is something I've never actually watched, but from what I understand is that it explains why it is necessary to have these dimensions.

I assume it is mostly useful in theoretical mathematics, as I don't see a mathematical application to a *physical* 4+ dimension

9. 1d is certainly a line
2d is a square
3d is a cube
Tv is a 2d picture of a 3d object, so it's a series of deformed squares that begin to resemble a cube because thats what one of our eyes might see
3d movies actually show 2 2d images to in stereo, 1 to each eye and that simulates 3d however it's also not true 3d as if you move left and right the image stays still
True 3d would be holograms which genuinely project 3d images without the need for glasses, etc or the real world
You may add 1 to each of these to add movement, because for movement you require time and physics show time to be equal to any of the spaceial dimentions

10. Originally Posted by ilostthesheriff
How does 2D get left at 2 axis when there is a percievable depth to it? Or is it based on a law of science?
i think you're confusing the illusion of depth for the physical reality (as when you mentioned the photograph).
it's worth remembering that photographs, books and all etcs are just illusions/representations of reality.

at least you now know that you have the right to a refund for that '3D' movie you watched.

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