View more

View more

View more

Image of the Day Submit

IOTD | Top Screenshots

The latest, straight to your Inbox.

Subscribe to GameDev.net Direct to receive the latest updates and exclusive content.

2D Coordinates from 3D View and Projection Matricies

Old topic!

Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.

#1Your1 Nightmare  Members

Posted 25 March 2012 - 03:06 PM

In a game I am developing with a team I ran into some issues regarding Matricies and finding coordinates in the game world based off of a resolution. I am trying to constrict a ship so that it does not leave the game screen, however these bounds will change based off of the resolution of the game screen. This is what we have been thinking so far:

V = view Matrix
P = projection Matrix
M = V * P

s = screen space coordinates
w = game world space coordinates

w * M = s

I then took the inverse of M with s so i could figure out the corner of the screen in "w". I split the coordinates using x = w.X * w.W and y = w.Y * w.W, because it was a 4th dimentional vector.

w= M^-1 * s

#2pilarsor  Members

Posted 28 March 2012 - 03:00 PM

Keep in mind, that your matrix M transforms each point into homogeneous clip space HCS, ranging from
x=-w..w, y=-w..w, z=-w..w,w=z, so you might want to devide each projected coordinate additionally by w, to get
your screen values in range x=-1..1,y=-1..1,z=-1..1, the normalized device coords ( NDC ).

So:

M*w = c (in HCS)
s = c / c.w ( divide by homogeneous coordinate c.w )

To get back into world space, store your c.w per fragment/pixel/screen coord.

For each screen coord:
c = s * c.w
w = M^-1 * c

Old topic!

Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.