forums.ps2dev.org

[psiko_scweek]

ok i have my objects moving based on speed and direction...
and i want them to bounce when they reach the side of the screen.
here is my bounce code thus far, its not as accurate as it should be...

can anyone help me?!

[arrggg]

assuming:
Begining angle 45 = after bounce 135
Begining angle 80 = after bounce 100


function object.bounce(o)
o.dir = (90 + (90 - (o.dir)) )
if o.dir < -360 then o.dir = o.dir+360 end
end

This is untested.

[KawaGeo]

I wrote an algorithm for ball bouncing in other language. No time to dig up where I put it on my 160GB HD. But here is a hint:

Say the moving ball has a new position (x2,y2) to move from the previous position (x1,y1). If x2 is outside of the vertical wall, mirror it and keep y2 unchanged. Likewise, for y2. Best way to figure out is to draw a diagram to measure the bouncing off the wall.

Treat my hint as your homework. :)
_________________
Geo Massar
Retired Engineer

[arrggg]

[psiko_scweek]

alright

[Durante]

if you only have horizontal and vertical walls do it like KawaGeo suggested, or, alternatively, if you want to use polar coordinates for the ball direction use my method from Crystalise (hor == horizontal wall, use 180 instead of math.pi if you use degrees):

[KawaGeo]

[psiko_scweek]

ok, this is prolly going to sound very very noobish..and for that im sorry...

ive read about normals and vector math and the such but i dont understand it, if someone could give me and example of how to find the normal of something i would really appreciate it.

a simplified explanation would work as well...heh

let me reiterate that im not asking anyone to do this for me, i just learn better by example, thats all.

thanks in advance!
regards,

PSIKO

[KawaGeo]

Wanna examples?

We have plenty. Nearly all Lua scripts are open-source. They are good examples. Visit http://psp-news.dcemu.co.uk/ at the left side. You might want to "study" one called Jezzball. I haven't take a look at it yet. I think it is a good example - lots of balls bouncing around.

Have fun.

PS Real balls, mind you!
_________________
Geo Massar
Retired Engineer

[psiko_scweek]

thanks for that suggestion,
ill check that out tomorrow after i get out of work!

thanks again, hopefully you will see a game from me soon enough!

Regards,

PSIKO

[Zenurb]

I did normals and things in high school physics, I could be (and am probably) wrong, but isn't the normal of a surface, 90 degrees from it? say you have a horizontal line


----------------------------------



the normal would be

[KawaGeo]

Yes and 90 degrees around the normal on the surface in 3-D scene like a telephone pole.
_________________
Geo Massar
Retired Engineer

[Durante]

RE finding the normal of a vector in 2D:
That's actually very simple, given v = (a, b) the normal vectors are (-b, a) and (b, -a).

For 3D look here

[psiko_scweek]

ok so the normal of a surface is a line

[KawaGeo]

Let's take a step a time, ok?

What Durante meant is that v is a vector like an arrow, starting from the origin point (x0,y0) to the destination point (a,b). If you draw a diagram, you would understand better. Draw x-axis and y-axis lines. The intersection is the origin point. Mark 'a' on the x-axis and 'b' on the y-axis. Draw an arrow from (x0,y0) to (a,b). Remember v is not a number but just a line and both a and b are numbers. Now, come the normal vectors: (-b,a) and (b,-a). What the hell are they? They are just vectors or arrows. Say the first starts from (x0,y0) to (-b,a). Remember '-b' which is the first element of (-b,a) is ON the x-axis and the second is on the y-axis. Draw that arrow. You'll see that the normal vector is perpendicular (90 degrees) to the given vector. You do likewise for the second normal vector. I hope I made it clear.

If you dont understand something, draw a diagram like I always did during my engineering career.
_________________
Geo Massar
Retired Engineer