I'm reading the book "Learn Unity for 2D game development", and I don't know how to do this:
"The camera has been aligned in the world so that the screen space origin is at the bottom-left corner; meaning positive X spans across the screen width, and positive Y across the screen height from bottom to top."
I'm new on Unity and the book doesn't talk how to do it.
By the way, I'm using Unity 4.3.3f1 on a Windows 7.
How can I align the camera to make screen space origin at the bottom-left corner?
In a 2D game, you have an X-axis and Y-axis. When increasing an object's X-value, you could say the object is going right. When increasing the Y-value, you could say the object is going up.
In a 3D game, there is another additional axis, the Z-axis. This makes it possible to gain 'depth' in games.
Example:
If you wanna create a 2D game in a 3D environment, you'll have to 'remove' one of the axis. The most common is to remove the Z-axis to keep the naming in line (X and Y remain, like in a 2D game).
To achieve 'removing' an axis in a 3D environment, your view has to be looking straight at it. In this case, X and Y rotation can be anything but your Z rotation has to be 0.
Example:
Consider the above picture to have a Z-axis as well. But because you are looking from Z=0 towards the origin, the line doesn't go to the right, left up or bottom. The axis will be like 1 pixel size.
When you do this using the camera, in such a way that the world origin is in front of you and higher X numbers are to your right and higher Y numbers are above you, you've achieved this. This also means that the screen's value of X=0 is totally left, and the screen's value of Y=0 is totally bottom. This concludes that space origin is at the bottom-left corner; meaning positive X spans across the screen width, and positive Y across the screen height from bottom to top.
By saying "camera has been aligned", he doesn't mean that you manually align it in the scene, he's saying how screen space origin is at the bottom-left corner by default.
Source: Unity Script Reference
Related
Say my camera is rotated around the X axis 60 degrees and looking down on a 9x9 block chess board. As we adjust board size, I want to zoom out the camera. Say for arguments sake the camera's position is (4,20,-7) and like this the whole board is visible and taking up the full screen.
If I adjust my board size to say 11x11 blocks I will now need to zoom out the camera. Say I want to maintain the same 60 degree angle and want the board to fill as much of the screen as it did before. What should the camera's new position be and how do you calculate it?
The X part is easy since you simple give the camera the same X position as the middle of the board. I'm not sure about how to calculate the new Y and Z positions though.
Any advice appreciated. Thanks.
edit: and if i wanted to change the angle of the camera as well as zoom out, is that possible to calculate? this is less important since i'll probably stick with the same angle, but i'm interested to know the maths behind it anyway.
Transform.Translate() method will move the transform according to the rotation. So you don't have to worry about the direction where your camera is looking at, just
yourCamera.transform.Translate(Vector3.forward * moveAmount);
will move your camera forward, which means zoom in. If you want to zoom out, just change the sign of the value to minus.
When I didn't know this, I used Mathf.Sin() and Mathf.Cos() to calculate each y and z world coordinates, which sucks.
I'm creating a 2D game in unity, but my origin is the center of the screen, meaning that my x and y values in the transform can be negative. I want to move the origin to the bottom-left, so my x and y values are always positive. How do I do that in Unity?
Figured it out. Had to move all my objects to the bottom-left of the game canvas, since the game canvas is what determiens all the objects positions -- not the camera!
Referring to the image above. I have a Red Node at the center of the screen with a distance of 1.0 unit (1 meter away) [See iPhone Portrait Top View]
What I do is I capture a screenshot of the iPhone screen and the resulting image is 750 x 1334 pixels [See iPhone Portrait Front View]
sceneView.snapshot()
What I want to do is put 4 Red Square Nodes located on the four sides of the iPhone screen relative to the Red Circle (at the dead center of the screen). I am making this to mark where I did a snapshot. What I want to know is how can I plot a box node precisely at a certain x,y point given z distance. (The value of Z is not fixed, I just used 1.0 as a sample scenario).. I want to plot (0,0), (750,0), (0, 1334) and (750, 1334) at a given z of 1.0 and assuming I am on a tripod, the plotted nodes would appear on the four sides of my iPhone screen.
I am very terrible at math and this problem is so complicated for me to solve alone with my current math skills. Can anyone help? Please?
Since you need ARnchor nodes (to mark where a snapshot was done) using the real time information from the camera instead of a snapshot would be probably easier. In special due to pixels in a 2D image are referenced from left to right and from top to bottom (with "0,0" coords located in the top left side)
... and we know the AR nodes are referenced in 3D coordinates with the center of the local node as the 0,0,0 coords.
I haven't yet code to test but I think the following properties should help:
let pPoint = sceneView.projectPoint(self.centerBall.position)
let fieldW = sceneView.session.currentFrame?.camera.imageResolution.width
let fieldH = sceneView.session.currentFrame?.camera.imageResolution.height
The "pPoint" should return the 2D coords corresponding to the (0,0,0) 3D coords of "centerBall" from there it should be just add or subtract calculations to obtain all 4 corners in 2D
Finally passing the 2D coords of every corner to the "unprojectPoint(:)" method should provide the 3D "world" coords and that can be converted to "centerBall" coordinates with the "convertPosition( position: SCNVector3, from node: SCNNode?)" method
It seems interesting so will try to code this before weekend
At the end I suspect ARanchor nodes may not be 100% stables
So I've developed games in other platforms where the x/y coordinate system made sense to me. The top left representing the game screen with coordinates of (0,0) and the bottom right was (width,height). Now I'm trying to make the jump to Unity 2d and I can't understand how the game screen works. If I had a background object and a character object on the screen, when I move the character around his x and y values vary between -3 and 3... very small coordinates and it doesn't match the game resolution I have setup (1024x768). Are there good tutorials for understanding the game grid in Unity? Or can anyone explain how I can accomplish what I'm trying to do?
There are three coordinates systems in Unity: Screen coordinates, view coordinates and the world coordinates.
World coordinates: Think of the absolute positioning of the objects in your scene, using "points". You can choose to have the units represent any length you want, for example 1 unit = 10 meters. What is actually shown on the screen is determined by where the camera is placed and how it is oriented.
View Coordinates: The coordinates in the viewport of a given camera. Viewport is the imaginary rectangle through which the world is viewed. These coordinates are porportional, and range from (0,0) to (1,1).
Screen Coordinates: The actual pixel coordinates denoting the position on the device's screen.
Note that the world co-ordinates of any given object will always be the same regardless of which camera is used to view, whereas the view coordinates depends on the camera being used. The screen coordinates in addition depend on the resolution of the device and the placement of the camera view on the screen.
The "Camera" object provides several methods to convert between these different coordinate systems like "ScreenToViewportPoint" "ScreenToWorldPoint" etc.
Example: Place object on top left of screen
float distanceFromCamera = 10.0f;
Vector3 pos = Camera.main.ScreenToWorldPoint (new Vector3 (0, Camera.main.pixelHeight, distanceFromCamera));
transform.position = pos;
The ScreenToWorldPoint function takes a Vector3 as an argument, where the x and y denote the pixel position on the screen ( 0,0 is the bottom left) and the z component denotes the desired distance from the camera. An infinite number of 3D locations can map to the same screen position, so you need to provide this value.
Just make sure that the desired position falls within the clipping region of the camera. Also, you might need to pick a proper pivot for your object depending on which part of your object you want centered on the top left.
Using:
Camera.main.WorldToScreenPoint (transform.position);
Let's me convert my GameObjects tranform position to the screen's x and y coordinate system
I am new to Cocos2D on iPhone. I see that Cocos2D uses a coordinate axis where 0,0 is at the bottom left corner and X positives are to the right and Y positives up.
Now I have created a sprite and added several sprites as subsprites of this one. For my surprise the subsprites appear mirrored in Y!!! The point 10,10 will be on the upper left corner of the sprite!!!
I can simply flip the sprite in Y to make it follow the same screen coordinate, but then the content will be reversed.
Is this a bug or what?
thanks.
Without seeing any example code is a shot in the dark, but I think you need to use Anchor points.
Each sprite has an anchor point of x, y.
ccp(0.5f, 0.5f) would be the center of the sprite.
(0,0) is the bottom left....(1.0f,1.0f) is top right etc.... Over 1.0 goes outside the sprite.
Child nodes (CCSprite) will use their anchor point on the parent node coordinates.
MySprite.anchorPoint = ccp(0.5f,0.5f);