#pragma kernel CSMain

#include "UnityCG.cginc"

#define WORK_GROUP_SIZE 1024

struct Vertex
{
	float3 position;
	float3 normal;
	//float4 color;
	//float2 uv;
	//float2 uv2;
	float4 tangent;
};

CBUFFER_START(Variables)
	int index;
	int count;
	float4x4 model_matrix;
CBUFFER_END

RWStructuredBuffer<float4> home_buffer;
RWStructuredBuffer<float4> home_velocity_buffer;
RWStructuredBuffer<Vertex> vertex_buffer;

[numthreads(WORK_GROUP_SIZE, 1, 1)]
void CSMain(uint3 id : SV_DispatchThreadID)
{
	uint offset = (uint)index;
	if (id.x < offset || id.x >= offset + count)
		return;

	float4 pos = float4(vertex_buffer[id.x - offset].position, 1);
	pos = mul(model_matrix, pos);

	float3 last_pos = home_buffer[id.x].xyz;
	float3 vel = length(last_pos) == 0.0f ? float3(0, 0, 0) : pos.xyz - last_pos;
	home_velocity_buffer[id.x] = float4(vel, 1.0f);

	home_buffer[id.x] = pos;
}