How to control the number of particles depending on how much you open your mouth

Hey Reiya,

You can use Face Landmarks template to create the effects that you're looking for.

Here is the step by step on how to do this using Face Landmarks template:

First let's just delete everything in the objects panel but only keep these objects:

The Mouth Distance is all you need to find the distance between top lip and the bottom lip so we can make an interaction based on that distance.

Than I added a particle system and set it as a child of our head binding in the Objects panel.

Make sure not to move the Headbinding and if you want move or manipulate the particle, use the particle object it self to move or manipulate.

Then select the Mouth Distance object and create a script on that by clicking on add new component and select script.

Then create a script and add it to the component.

And now we need to do a small scripting. Double click on the script to open it in the script editor and then paste the script below:

// -----JS CODE-----

// @input Component.ScriptComponent distanceScript {"label":"Distance Script"}

// @input Asset.Material particleMaterial

// @input float amountMultiplier = 1000 {"widget":"slider", "min":0.0, "max":3000.0, "step":0.1}







var getDistanceFunc = null;

var particleMainPass;

var init = false;







function onLensTurnOn(){

getDistanceFunc = script.distanceScript.api.getDistance;

particleMainPass = script.particleMaterial.mainPass;

init = true;

}




function onUpdate(){




if(init)

{

var distance = getDistanceFunc();

particleMainPass.spawnMaxParticles = distance * script.amountMultiplier;

}




}



var turnOnEvent = script.createEvent( "TurnOnEvent" );

turnOnEvent.bind(onLensTurnOn);




var updateEvent = script.createEvent( "UpdateEvent" );

updateEvent.bind( onUpdate );

Then save the file.

Now we need to set the Distance script and the particle material.

Then set the Amount Multiplier to be around 1000 and now it should be working!

I also attach the project file for you here. 

https://storage.googleapis.com/snapchat-lens-assets/f1a09194-f02d-43ed-92b8-62e843179ff0/lensStudio/Forum-Helpers/Face-Landmarks-Particles.zip

But I recommend to do it with the step by step guide here and let me know if you have any problems.

Also you can learn more about Face Landmarks here:

https://www.youtube.com/watch?v=IyBMuU-U58c

https://lensstudio.snapchat.com/templates/face/face-landmarks/

Hope this will help and have fun creating lenses.

Cheers,

Amir.