basic MEL help please

# 1 25-07-2004 , 02:23 AM

Registered User
Join Date: Jul 2003

Location: Australia

Posts: 50

Hi there.

I want to create the effect of sheet lightning, by randomising the intensity of a point light.

I can get this to happen, but i need it so that i can vary the time between flashes, like i need an avg random 30 frames between changes.

i came up with this, having not much programming or MEL experience,

//setup values
int $mycount;
$mycount = rand(20,30);
int $i;

//loop for 380 frames
for ($i=1; $i <380; $i++) {

//check random value against frame value
if (frame == $mycount) {

//change light intensity
pointLightShape1.intensity = rand(0,1);

//increase random value to progress
$mycount += $mycount;
}
}

and now I'm stuck. can anyone point out where i went wrong?
it only changes the intensity once. and then not even everytime i play it through.
or perhaps a less round about way of doing it?
thanks!!

Adam.

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# 2 25-07-2004 , 05:24 PM

Subscriber
Join Date: Jul 2002

Location: MELville

Posts: 1,100

wait.. let me first try to figure out what youre trying to do..... as the animation plays, you want random flashes every 30 frames?

-Emo

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# 3 26-07-2004 , 02:05 AM

Registered User
Join Date: Jul 2003

Location: Australia

Posts: 50

a random vaule for the illumination yes.

and approximately every 30 frames. I wanted to randomise the time between flashes. so approx 30 frames, say a random interval between 10 and 40.

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# 4 26-07-2004 , 08:52 AM

Moderator
Join Date: Oct 2002

Location: London, UK

Posts: 2,800

this would be easier as an expression:

right click the intensity in the channel box and add this:

if(frame % 30 == 0)
{
pointLightShape1.intensity = rand(0,5);
}

What you are doing is using the modulus function (%) to check if the frame divides equally by thirty and then setting the intensity by expression.

Simple user added image

Alan

Technical Director - Framestore

Currently working on: Your Highness

IMDB

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# 5 26-07-2004 , 11:18 AM

Registered User
Join Date: Jul 2003

Location: Australia

Posts: 50

thanks Alan!
i was at a bit of a loss how to do the time delay properly.
that would only make it exactly 30 frames though?
i want it to be more random than that.

like lightning
a couple of quick flashes, a pause, flash, pause, some more quick, or whatever.

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# 6 26-07-2004 , 12:37 PM

Moderator
Join Date: Oct 2002

Location: London, UK

Posts: 2,800

well if you want it that specific then you may have to key it. You can use a random number instead of the frame number:

int $frameChange = rand(10, 40);
if(frame % $frameChange == 0)
{
pointLightShape1.intensity = rand(0,5);
}

Alan

Technical Director - Framestore

Currently working on: Your Highness

IMDB

Quote

# 7 27-07-2004 , 12:21 AM

Registered User
Join Date: Jul 2003

Location: Australia

Posts: 50

no no, not specific, random is what i want.
that random function should work a treat,

thanks for that Alan.
I really appreciate the effort you make helping out me and other newbies.

this is what i ended up with, if anyone was interested in how it ended up working.

//setup values

int $mynumber;
int $i;

//loop for 380 frames

for ($i=1; $i <380; $i++) {

$mynumber = rand(50,80);

if (frame % $mynumber == 0) {
pointLightShape1.intensity = rand(0,1);

//increase random value to progress

$mynumber += $mynumber;
}
}

Last edited by Binabik; 27-07-2004 at 12:38 AM.

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basic MEL help please

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