# jME3 Math for Dummies (Complete)

Very nice norman, this is a good help.

Perhaps some notes about projecting would be nice.

Like

• you have a vector A (1,1,1), which Vector would it be projected on the X-Plane?

Usefull for e.g. minimaps.

Regards
snareoj2 said:
Very nice norman, this is a good help.
Perhaps some notes about projecting would be nice.
- you have a vector A (1,1,1), which Vector would it be projected on the X-Plane?

Thanks! I guess projection would go into an "Advanced Math for Dummies" tutorial, along with dot product and other things. This is mainly meant to solve the basic spatial translating and rotating problems. And just call me by my name, normen ;)
nego said:
btw its grown nicely now, good work
slide 30, last point where you create a quaternion from "axes", its supposed to be angles i think

Thanks! I'm lost without code completion ;)

Np, so quaternion.lookAt() will rotate ALL possible input vectors around the UP- axis to the direction specified?

No, it will rotate only the vector that is perpendicular (around X) to the up vector into the right direction. This is mainly used for spatials where āforwardā is Z and up is Y. Quaternions are relative rotations of the Z direction vector of the spatial.

1 Like

Ahh, now i get it, tyvm! I used it quite often for setting directions, now i know how it works, thx!

nego said:
Ahh, now i get it, tyvm! I used it quite often for setting directions, now i know how it works, thx! :)

I re-edited the lookAt section a bit based on your input, explaining it in a slightly more general way.

ā¦ aaand I couldnāt resist starting this one too: SceneGraph for Dummies I donāt know when I will finish it thoā¦ but its so much fun maybe it happens soon ^^

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And thank you for such a good tutorial!!!

SceneGraph tutorial, page 22:

Now we rotate the node by 90 digreesā¦

[java]

spatial.rotate(0,0,FastMath.HALF_PI);

[/java]

But, possibly there should be node instead of spatial?

[java]

node.rotate(0,0,FastMath.HALF_PI);

[/java]

Edited: and have a look at page 28 too.

1 Like
mifth said:
SceneGraph tutorial, page 22:

Now we rotate the node by 90 digrees...

[java]
spatial.rotate(0,0,FastMath.HALF_PI);
[/java]

But, possibly there should be node instead of spatial?

[java]
node.rotate(0,0,FastMath.HALF_PI);
[/java]

Edited: and have a look at page 28 too.

Nodes are spatials. :)

Heh, yeah, I dont create the variables in this example so I could pretend it was no error ^^

But I am very thankful for these corrections, after looking at the page for the 10th time they just become invisible to meā¦

Thanks for this, could come in handy for some quick ref, especially for the quaternions

Hi, Normen!!!

I think, I found a mistake on a picture: page 14.

Image of C=A+B looks the same as C=A-B.

But it should looks like:

http://imageshack.us/photo/my-images/849/ma33.jpg/

Uploaded with ImageShack.us

Nope, the tutorial is fine.

Possibly, there are problems with my linux or firefox5.

Iāve got such an image:

http://imageshack.us/photo/my-images/35/matheqc.jpg/

Uploaded with ImageShack.us

Which is perfectly fine, Vector B has been moved to show its length. Play the presentation in Safari to see the animations.

ahhh, THANKS! Animation does not work with firefox. I tried reconq browser and it works.

gj @normen these rock, I have used them a lot :P, and they are very useful. We need to make more of these presentations. A quick list which I think would be useful for people would be: Physics for dummies (equations of motion, collisionshapes, applying forces (velocity), using kinematic objects, acceleration/deceleration), Shaders for dummies (simple vertex, fragment shaders), Networking for dummies (communication protocols (TCP, UDP), how networks work), pretty much anything could be for dummies :]

The presentation says that itās not available any more.

Ā