Emitting

[martin951]

this is a great trail addon but please make it possible to stop emitting.

[zhifez]

Lol, I was here to see if anyone had the same problem as I do.

At first I tried setting its visible to false, but there'll be a visual bug (from when it's not visible) when I make-visible and re-emit the trail.

A quick workaround I did now is to store the trail's length value, set it to 0 when I want it disabled, then back to its old value when I want it enabled.

[Turudihan]

Well, I just modified shader code, so it brings trace_active parameter. Turn it on to start emitting new traces. Just remember to restart
emission, while after you have done it.

shader_type particles;

render_mode keep_data,disable_force,disable_velocity;

uniform int trace_active : hint_enum ("Off", "On"); // добавленная переменная (управляется извне)

void process() {
	// CUSTOM.w tracks the particles place in the trail, in range (0..LIFETIME]
	// requires that LIFETIME = number of particles
	float amount = LIFETIME;

	vec4 a = EMISSION_TRANSFORM * vec4(0,1,0,1);
	vec4 b = EMISSION_TRANSFORM * vec4(0,-1,0,1);

	
	// start
		if(CUSTOM.w == 0.0){
			CUSTOM.w = float(INDEX)+1.0;

			// needed to pass to draw pass
			CUSTOM.z = amount;

			// needed to initialize in case of CUSTOM.w == 2.0
			TRANSFORM = mat4(a,a,b,b);
		}
	if (trace_active == 1) {
		// restart
		if(CUSTOM.w == amount+1.0){
			CUSTOM.w = 1.0;
		}

		if(CUSTOM.w == 1.0){
			// sets the quad to the line to cache this frame, it is not yet visible
			TRANSFORM = mat4(a,a,b,b);
		}

		if(CUSTOM.w == 2.0){
			// sets the right edge of the quad
			TRANSFORM[1] = a;
			TRANSFORM[2] = b;
		}
	}
		CUSTOM.w++;

}