#version 460 core
#define STAGE_COMPUTE 1
// the water on the windscreens (water_sim.glsl): the drops which gathered others take their water, move to the middle of it and
// slow down as much as the still water slows them; the header of the glass tells the glasses it's simulated. a thread per drop,
// a row of groups per glass

#include "common.glsl"
#include "water_sim.glsl"

layout(local_size_x = WATER_GROUP_SIZE) in;

void main()
{
	uint slot = gl_WorkGroupID.y;
	uint place = gl_GlobalInvocationID.x;
	if ((water_slots[slot].z < 0.5) || (place >= uint(WATER_DROPS)))
		return;
	if (place == 0u)
		water_header[slot] = vec4(1.0, water_step.y, 0.0, 0.0);
	uint index = slot * uint(WATER_DROPS) + place;
	int gathered = water_gather[index * 4u];
	if (gathered == 0)
		return;
	vec2 moment = vec2(float(water_gather[index * 4u + 1u]), float(water_gather[index * 4u + 2u])) * 1e-6;
	water_gather[index * 4u] = 0;
	water_gather[index * 4u + 1u] = 0;
	water_gather[index * 4u + 2u] = 0;
	water_drop_s drop = water_drops[index];
	if (drop.place.z <= 0.0)
		return;
	float volume = drop.place.z + float(gathered) * 1e-4;
	drop.place.xy += moment / volume;
	drop.motion.xy *= drop.place.z / volume;
	drop.place.z = volume;
	water_drops[index] = drop;
}