# jME3 Math for Dummies (Complete)

Hey,

I started working on a document to visualize the basic vector / math concepts in jME3 for the absolute beginners, tell me what you think: Link to presentation.

If you cant see the bottom part in full screen mode, make your browser window more narrow, somehow it only reacts to width, not height.

I want to add interpolation and some more rotation things as well as lookAt still, any other things you think should be definitely in?

Cheers,

Normen

Edit: Also check out the new and in progress SceneGraph for Dummies presentation.

4 Likes

I love it, just feels like being in kindergarten again hehe

If you substract the location B from the location A, you get the directional vector from A to B (or whas it the other way around? ), thats definitely something you should know :).

Hmm one more basic princible i would add is the difference between local and world transforms, but that isnt math ofc.

Thanks! Yeah, maybe a â€śSceneGraph for Dummiesâ€ť would be cool too

btw its grown nicely now, good work

i think i encountered an error (not a big deal, just a typo)

slide 30, last point where you create a quaternion from â€śaxesâ€ť, its supposed to be angles i think (and the method is then q.fromAngles(float [] angles)

Rapidly skimmed and I found it very interesting.

Thereâ€™s a question that popped up though in frame 31.

The Quaternion C (quatC) in the picture shows all 3 axis have rotated. From what I have seen and understood in those frames, I think only the Z and Y axis should have rotated right? If so maybe removing the X rotation diagram would remove any confusion.

Itâ€™s nitpicking I agree, but as I said before, Iâ€™m visual, and itâ€™s that kind of thing that attract my attention immediately and could possibly confuse meâ€¦

Yeah, it was more meant like â€śsome quaternionâ€ť, its a complete image so its not so easy to change, have to fire up photoshop etcâ€¦ Just now uploading an updated version, only lookAt is missing now I guessâ€¦ Maybe an advanced section explaining dot products etc. would be nice in the future, but its probably beyond the scope of this basic introduction.

There are some videos on YouTube about dot products and vectors and other math stuff made by someone named â€śkhanâ€ť, they are very good. The commenter is also easily able to vulgarize some of that stuff.

Maybe you could look those up and link them at the end of that presentation.

Just an idea.

This is great! A lot of developers we try to get into 3D programming often have problems with the properties of rotations. The explanations you provided seem very rational to me

Very helpful! Iâ€™m still a bit confused about quaternions, but I only read it once. Iâ€™ll get it once I read it a couple of times Thanks!

nomnom said:
Very helpful! I'm still a bit confused about quaternions, but I only read it once. I'll get it once I read it a couple of times ;) Thanks!

Then you will surely have to explain it to the rest of us. :) I've used quaternions for years and still have little idea on how they work. I just know that they do and when to employ them.

In adition to what nego said, perhaps you also want to mention the normalize functions, I use them often for any 3d programming Quickly went trough your presentation and didnâ€™t see any mention about that (tho the inerpolation function shown was new for me, lovely what you can learn from simple stuff)

Looking good otherwise =]

Very useful!!

Good idea!

I think I have found some mistake on page 24.

you say:

quatA.fromAngleAxis(FastMath.HALF_PI,... -> rotation of 90Â°
and
quatB.fromAngleAxis(FastMath.QUARTER_PI,... -> rotation of 90Â°

The second must be 45Â° and the image also must be changed
1 Like

Darn copy&paste thanks!

Well I hope this makes sure we donâ€™t get that much basic math questions anymore, great work.

Okay, I added everything, more would probably keep people from actually reading it

LookAt is a bitch to explain tho any ideas how to make that a bit better / more clear?

I added this to the wiki btw, it should display the full presentation inside the wiki now:

https://wiki.jmonkeyengine.org/legacy/doku.php/jme3:math_for_dummies

(handy link to help people help themselves ;))

Thanks @all for the feedback!

Cheers,

Normen

Iâ€™m trying to read this as a noob and thatâ€™s pretty hard as it turns out. I got into the vector part where you add two together and tell me the length is 1.4. Noob-me said, â€śHuh, why 1.4?â€ť Is it worth talking about A^2 + B^2 = C^2?

I kept trying to decide why if noob-me knew Pythagorean theorem then why didnâ€™t noob me already know about Vectors. And 1.4 seems pretty magic otherwise.

â€¦maybe thatâ€™s just a good place for a link to another resource?

Yeah, I keep some math aspects outside or expect knowledge about them so to speakâ€¦ Like I donâ€™t explain why 0.75 = 75% = 3/4 or why PI = 180Â° etc. I also never really do or explain the math but the cool thing about the API is that you can really forget about these basics I was reading it as non-wiki-reader-forum-poster and I figured if there would have been more text or complicated math Iâ€™d have posted in the forum

Then again, if .75 == 3/4 doesnâ€™t make sense to you, then youâ€™ve got bigger problems than making a game in jME

1 Like

I agree with the above.

There are noobs and then there areâ€¦ Iâ€™ll stay polite and keep what I wanted to say to myself.