Laser Whip

For those played Raiden 2 or 3. Or Most Raiden series. You most like; seen this

( around 1:40)

I want to do this laser whip. How would I got about do that?

make a segment of laser, like if you could cut a small square out of the raiden laser going straight upward

create a distort map for it, 1 across, however many segments you want down (try 10)

create 2 different sprites to use as a bezier control point and an endpoint (we'll call them sprite1, and sprite2)

make a bezier curve using the quadratic function (qarp)and the locations of the 2 sprites and the an imagepoint on the nose of your ship

if you need help understanding what you're doing a little better, read some of this wikipedia article, especially the little moving diagrams near the end

but for practical purposes what you will do

is set each segment of your distort map in this way

h=half the width of your laser

for 0 to NumberOfSegmentsOfDistortMap

set displacement (real) column(0)row(loopindex)

x to qarp(ship.imagepointx(nose)-h, sprite1.x-h, sprite2.x-h,1-loopindex/NumberofRowsindistortmap)

y to qarp(ship.imagepointy(nose)+h, sprite1.y+h, sprite2.y+h, sprite2.x-h,1-loopindex/NumberofRowsindistortmap)

set displacement (real) column(1)row(loopindex)

x to qarp(ship.imagepointx(nose)-h, sprite1.x-h, sprite2.x-h, sprite2.x-h,1-loopindex/NumberofRowsindistortmap)

y to qarp(ship.imagepointy(nose)+h, sprite1.y+h, sprite2.y+h, sprite2.x-h,1-loopindex/NumberofRowsindistortmap)

this will bend your sprite along a curve beginning at the nose of your ship

and ending at sprite2, and the curve will be guided by sprite1

always

set sprite1.x = ship.x, and sprite1.y = to ship.y + a number that makes the ray look cool

sprite 1 will be guiding the laser, so if you want it to lean toward y, subtly the way it does in raiden this is a good way to start

set sprite2.y = 0 (top of the screen), and sprite2.x to ship.x + a number that changes when you're moving to the right or left, you can decide exactly how you want this to look

you can also add small random values to either control point for a wobbly effect

use an instant bullet aimed at sprite2 to check for hits

once you hit an enemy ship, set sprite2's position to the position of the ship

and make sprite1 move drastically to the right or left as your ship does

if you need more details on any of the steps I can help you, but I can't post a cap just now

if you get this far, you may notice something a little different about the bending of the ribbon

because we're using parallel lines, the fix is simple, and takes only a minute, but might be confusing in the middle of this

Wow, wall of text. Thanks, I'll try it out.

ok, here's a simple cap

example

I think you will be pleasantly surprised by how short it is

it sounds more complicated than it is

please examine it, and let me know what parts, if any you need help with

to test, drag and drop the ship and the two control points

click here to download

Doesn't work if I make the laser have an effect.

you can try putting the laser on it's own layer

and applying a layer effect to that layer

The problem with using distort map is that it doesnt support distorted collisions

: what you're left with is a collision box which is a ghost of the undistored object. I would recommend using a chain of sprites.

davioware

or maybe a chain of invisible sprites for collision detection?

I haven't tried the chain of sprites thing yet, does it come out looking smooth?

What about pasting it to a canvas and using the canvas for collision? Haven't tried it, just theorizing.

deadeye

It would work theoretically, but depending on game window size having a full screen canvas is never the best idea.

deadeye

It would work theoretically, but depending on game window size having a full screen canvas is never the best idea.

True, but the game shown in the video looks to be about SNES resolution, which isn't too big. Plus, you only need the canvas when you have the whip active, yeah? You can spawn/destroy it as needed.

But if you can get a smooth looking chain of sprites then that's probably the most efficient way to go.

it's probably possible to make a chain of sprites and some distortion there to smooth it out if necessary without having the distortion change the collision much

just to fix the connecting edges

I don't know...I just haven't seen the smooth sprite chain done yet (or if I did, I didn't know it)

may be misplaced skepticism

Quazi's blobber guy had a smooth chain of sprites for the hose on his nacho-cheese gun.

At least, the original did. If I remember correctly the newest version uses distortions. Anyway, if your segments are short enough the chain won't look too blocky.

I stand corrected:

http://dl.getdropbox.com/u/1013446/raiden2.cap

edit: although I think maybe a cubic curve instead of a quadratic might look cooler, and crazier

edit2: fixed cap, so now in start of layout you can choose the number of segments

also, in the last version I had a -10 pixel offset leftover from cutting and pasting

my blobber uses a canvas, a small one, and the sprite for the tube is positioned and pasted using a loop