Java-Gaming.org Hi !
 Featured games (83) games approved by the League of Dukes Games in Showcase (541) Games in Android Showcase (133) games submitted by our members Games in WIP (603) games currently in development
 News: Read the Java Gaming Resources, or peek at the official Java tutorials
Pages: [1]
 ignore  |  Print
 3d camera locking onto a target/z-targeting  (Read 1130 times) 0 Members and 1 Guest are viewing this topic.
SkyAphid
 « Posted 2013-01-01 02:42:40 »

So, I'm trying to recreate z-targeting from the zelda games in my own, and to do this I plan on using the lookAt function. Unfortunately, it's not working out for me, even if it is basic trigonometry.

I read the following articles on it:

http://www.euclideanspace.com/maths/algebra/vectors/lookat/index.htm
http://www.ehow.com/how_5717908_calculate-lookat-function.html

My problem is, even if I have the eye coordinates, and the target coordinates, I don't know what to do about the current target coordinates. All I have available to use are the Yaw and pitch of my camera, so I don't know how to take these and make the coordinates I need to get the proper dot product.

And even when I do get the dot product, I don't know what to do about the arccos. In the second tutorial, the author says he got his angle from the arccos of 10. Of course in Java, the input of arccos can't be over 1, so how do I get around this?

I'm sorry if these are obvious questions, my geometry teacher was terrible so most of my trig is self taught.

Thank you.

“Life is pretty simple: You do some stuff. Most fails. Some works. You do more of what works. If it works big, others quickly copy it. Then you do something else. The trick is the doing something else.” ~Leonardo da Vinci
Agro
 « Reply #1 - Posted 2013-01-02 01:50:17 »

Well, I'm hoping your 3D camera is first-person based, then it will be easier.

a 3D camera has pitch and yaw, but it can also be represented with a 3 dimensional vector. So, calculate the vector from your target to you, which is basically target.pos - camera.pos, and then you'd need to normalize it.

That's basically your directional vector, so now you need to figure out how to calculate the pitch and yaw values of the 3D vector. I've shown how to convert pitch and yaw to a 3d vector here: http://www.java-gaming.org/topics/pitch-yaw-to-directional-vector/27819/view.html

But now we need the inverse, which I don't really have an idea how to do. Read up and euler angles, and maybe you'll find something...

I'll post if I find anything.

LunaticEdit

Senior Devvie

Medals: 8
Projects: 1

 « Reply #2 - Posted 2013-01-02 01:57:17 »

I'm not a 3D guy so I don't know what functions your lib does, but in XNA I had a 3rd person camera that 'looked at' a center point. What I would do is start at the X/Y/Z center of the character and then apply rotation matrix. THEN I'd apply a move translation matrix to 'pull' the camera back out (and still be looking at the character in a natural way) which seemed to feel natural while playing around with it. Assuming your library has the function, you could then simply perform a 'look at' on the camera to then face the enemy, which I would imagine would give it that zelda-like field.

Here's what I did using the method above (minus look-at of course):

theagentd

« JGO Bitwise Duke »

Medals: 366
Projects: 2
Exp: 8 years

 « Reply #3 - Posted 2013-01-02 03:32:02 »

In case anyone's wondering, we solved this over Skype...

 1  2  3  4  5  6  7  8 `   public void lookAt(float targetX, float targetY, float targetZ){      float dx = targetX - cameraX;      float dy = targetY - cameraY;      float dz = targetZ - cameraZ;            yaw = (float)Math.atan2(dx, -dz);      pitch = (float)Math.atan2(-dy, Math.sqrt(dx*dx + dz*dz));   }`

Myomyomyo.
Roquen
 « Reply #4 - Posted 2013-01-03 16:09:57 »

Camera's aren't worth worrying about any performance issues so this is just informational.  Skipping euler angles, you have:

The lookat direction from the camera to target (the dx,dy,dz above).  Normalize that.  Cross it with your up vector (say y, so little computation) and that give the direction to the 'side'.  Normalize that. Cross side and lookat gives camera's up (no need to normalize...side and lookat are orthogonal).  Shove these three vectors into the matrix (row or columns depending on your convention) and you're done.

forward = (fx,fy,fz) = (dx,dy,dz)/sqrt(dx*dx+dy*dy+dz*dz)
side = (sx,sy,sz) = (-fz, 0, fx)/sqrt(fz*fz+fx*fx)
up = (ux,uy,uz) = (-fy*sz, fx*sz-fz*sx, fy*sx)

Assuming I didn't screw anything up.
theagentd

« JGO Bitwise Duke »

Medals: 366
Projects: 2
Exp: 8 years

 « Reply #5 - Posted 2013-01-03 16:39:25 »

Muh, matrix math is hard! xD The reason why I computed the angles was because I/we have a camera class that works like a first person camera with a yaw and a pitch. By computing those I can just feed those directly into the camera class and be done with it. Hmhmmm...

Myomyomyo.
Pages: [1]
 ignore  |  Print

You cannot reply to this message, because it is very, very old.

 Add your game by posting it in the WIP section, or publish it in Showcase. The first screenshot will be displayed as a thumbnail.
 Mr.CodeIt (24 views) 2014-12-23 03:34:11 rwatson462 (55 views) 2014-12-15 09:26:44 Mr.CodeIt (46 views) 2014-12-14 19:50:38 BurntPizza (91 views) 2014-12-09 22:41:13 BurntPizza (113 views) 2014-12-08 04:46:31 JscottyBieshaar (83 views) 2014-12-05 12:39:02 SHC (92 views) 2014-12-03 16:27:13 CopyableCougar4 (102 views) 2014-11-29 21:32:03 toopeicgaming1999 (161 views) 2014-11-26 15:22:04 toopeicgaming1999 (164 views) 2014-11-26 15:20:36
 Rayvolution 49x basil_ 29x HeroesGraveDev 28x BurntPizza 25x LiquidNitrogen 24x appel 18x kpars 18x princec 17x KevinWorkman 16x Riven 15x NegativeZero 14x kevglass 13x pitbuller 12x gouessej 12x Ecumene 11x KudoDEV 11x
 Resources for WIP gamesby kpars2014-12-18 10:26:14Understanding relations between setOrigin, setScale and setPosition in libGdx2014-10-09 22:35:00Definite guide to supporting multiple device resolutions on Android (2014)2014-10-02 22:36:02List of Learning Resources2014-08-16 10:40:00List of Learning Resources2014-08-05 19:33:27Resources for WIP games2014-08-01 16:20:17Resources for WIP games2014-08-01 16:19:50List of Learning Resources2014-07-31 16:29:50
 java-gaming.org is not responsible for the content posted by its members, including references to external websites, and other references that may or may not have a relation with our primarily gaming and game production oriented community. inquiries and complaints can be sent via email to the info‑account of the company managing the website of java‑gaming.org