AuthorTopic: A Matter of Perspective...  (Read 12027 times)

Offline Zizka

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A Matter of Perspective...

on: March 09, 2015, 05:21:01 pm
Hello guys!

I have a question about perspective.

Here's a screenshot of my game:


At the moment, I'm creating new elements to decorate things but I'm really struggling with the perspective.

Normally, you would have a single or many VP. With a "static" background like here though, I don't understand according to what angle I should create new elements and this is bothering me immensely.

Normally, I would be able to use a VP to give me an idea as to how to proceed but now I can't. I could use a strict side-view perspective (like Mario) but I don't like the way it looks.

Ninja Gaiden pulled it off nicely:


I can see some parallel lines here.

Where would be mine in my screenshot however?

Normally I'd have a VP like so:


But here I obviously don't.

So yeah, I'm confused.

Offline dpixel

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Re: A Matter of Perspective...

Reply #1 on: March 09, 2015, 05:46:05 pm
I don't think you would find a vp in a game like this.  I just googled Ninja Gaiden and I think your lines should be more like this:


And the shadows should be at the same angle depending which way your light is coming from.  In Ninja Gaiden, it coming from the front left.  In my edit it's coming from the back (top) left.

Offline Zizka

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Re: A Matter of Perspective...

Reply #2 on: March 09, 2015, 06:45:39 pm
Thanks for the reply, dpixel. Your edit looks cool.

Say I would want to integrate the following pipes:





Neither perspective would fit. What I'm trying to figure out, is at which angle I should draw stuff to make things look right and coherant.

Logically, if I base the perspective on dpixel's edit, I shouldn't be able to see the inside of the pipe, correct? I should just see its side.

Offline dpixel

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Re: A Matter of Perspective...

Reply #3 on: March 09, 2015, 07:29:06 pm
Probably something like this:

Offline Cyangmou

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Re: A Matter of Perspective...

Reply #4 on: March 09, 2015, 08:52:00 pm
IIf you are looking for the horizon line in ninja gaiden, there are various possibilities, since they don't pulled it off exactly (most probably because of limitations)

this might help:

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Offline PixelPiledriver

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Re: A Matter of Perspective...

Reply #5 on: March 09, 2015, 09:04:54 pm
Do some reading on Linear Projection and Perspective Projection.
The difference between them is where your confusion is coming from Zizka.
And knowing that it is, we seek what it is... ~ Aristotle, Posterior Analytics, Chapter 1

Offline Zizka

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Re: A Matter of Perspective...

Reply #6 on: March 10, 2015, 11:33:40 am
Oops, I just realized I might not have been very clear in my request.

The reason why I posted a picture of Ninja Gaiden is because I like the way you can see the ground like that. This is what I tried to reproduce in my game. I donít want to have a Mario-like view where you can only see the edge of the ground.

I realize there is no vanishing point in my screen. The reason why Iím seeking help is because I need to be able to determine at what angle I need to create my assets for the game.

Basically, I want to understand how I can tackle the various geometric forms in my game.
 
Say, if I had to do a cone, Iíd like to know which shape it should have so everything ends up looking good. Anyways, Iíll look up the perspective mentioned by PPD and Iíll let you know if I still donít get it.

EDIT: There's really not much out there. What's a good reference to read up about this stuff?
« Last Edit: March 10, 2015, 11:53:26 am by Zizka »

Offline Ai

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Re: A Matter of Perspective...

Reply #7 on: March 10, 2015, 12:04:28 pm
Most linear projections are 'orthographic' projections. Some are not, though.. notably oblique projections -- which are probably what we are dealing with here.

I put everything following this together before I realized it doesn't completely apply, however, there are still a lot of similarities between orthographic and oblique projections, so hopefully it can be of some use:

----

Orthographic projections are generally very simple : the angle of a line in the 2d projection always has the exact same relation to the angle the viewer is looking at. For example, all planes that are exactly perpendicular to the angle the viewer's eyes are pointing, are always completely invisible (dpixel's pipe edit demonstrates this principle); all planes that exactly face the angle the viewer's eyes are pointing, are completely visible (unless other objects obscure them directly) and unskewed. The same principle of a given angle appearing the same no matter where it is in the viewport, applies universally.

EDIT: Here's some samples rendered with blender with a similar camera to yours:

This includes 4 cones, a sphere, 3 torii, and a cube. All objects of the same type are identical duplicates.

This is the same scene, but with a camera angled 22.5 degrees to the right (so the object planes and camera planes no longer align perfectly)



You can see that I actually just chucked stuff in arbitrary locations to get it to fit nicely in the first camera's viewport, here ;)
But more importantly, hopefully, it gives a clear visual on what faces will always be visible, and what faces will never be visible, relative to any given camera angle.
« Last Edit: March 10, 2015, 01:01:23 pm by Ai »
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Offline Zizka

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Re: A Matter of Perspective...

Reply #8 on: March 10, 2015, 02:02:54 pm
Let me get this straight ???:

Linear projection are orthographic projections. Only, in the Ninja Gaiden screen, we're dealing with an oblique projection which is a linear projection but not an orthographic projection. Am I right so far?

dpixel's edit would be oblique projection:


While my original screen would be... orthographic projection?:


Quote from: ai
Orthographic projections are generally very simple : the angle of a line in the 2d projection always has the exact same relation to the angle the viewer is looking at. For example, all planes that are exactly perpendicular to the angle the viewer's eyes are pointing, are always completely invisible (dpixel's pipe edit demonstrates this principle); all planes that exactly face the angle the viewer's eyes are pointing, are completely visible (unless other objects obscure them directly) and unskewed. The same principle of a given angle appearing the same no matter where it is in the viewport, applies universally.

Ok, I think this is the definition I was looking for. I've saved both pictures to my hardrive by the way.

So this perspective:


...is equivalent to this one:


While this one:

...is equivalent to this one:


So basically, I have to choose either an oblique or orthographic projection and then stick with it, am I getting this right?

Quote from: ai
But more importantly, hopefully, it gives a clear visual on what faces will always be visible, and what faces will never be visible, relative to any given camera angle.

Well, it does give me an idea as to what faces will always be visible if I compare both pictures. It's just the angle of those faces I need to determine based on the model of projection I end up choosing.

Here's the thing:

More specifically, I want to add toilet rolls to the stage. I need to determine how to draw the top of the toilet roll.

Correct me if I'm wrong here:

This would be orthographic:


My question is: based on my screen, just how much of the top should I see? What's the eye level here? Should the top ellipse be the same as the one in the cone here:



Anyways, thanks for taking so much time for a thorough input!

Offline Kazuya Mochu

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Re: A Matter of Perspective...

Reply #9 on: March 10, 2015, 02:25:19 pm
a circle in perspective is always an ellipse, be it orthogonal or conical perspective. only if the circle is perpendicular to the camera direction will it be shown as a perfect circle.
What changes in the orthogonal perspective is that the center of the circle is the center of the ellipse, while in conical perspective, the center of the circle wont match the center of the ellipse.

this sort of perspective is like if you had a camera VERY far from the scene and zoomed in. theres still a vanishing point, but its so far away that you can't feel the distortion.
Image size doesn't matter! It's what you do with your pixels that counts!