## Simple shading problem

Hi,
I'm trying to do a simple cloth simulation based on the Opengl SuperBible.
We consider that we have vertices that are connected to each other.
For each vertice, we only consider perturbation due to 4 adjacents points.
In my code below I first try to find the index of each vertex being processed then its 4 neighbours that I put in connection array.

Than I simply apply physics laws.
The problem is that I have warnings :

0(31) : warning C7050: "connection[0]" might be used before being initialized
0(31) : warning C7050: "connection[1]" might be used before being initialized
0(31) : warning C7050: "connection[2]" might be used before being initialized
0(31) : warning C7050: "connection[3]" might be used before being initialized

I don't understand why the neighbours are not being initialized ?
And obviously the rendering result is not what I expected.

Code :
```#version 400
in vec3 position;
in vec3 velocity;

//Outs
out vec3 position_out;
out vec3 velocity_out;

//Uniforms
uniform float t;
uniform samplerBuffer tex_position;
uniform samplerBuffer tex_velocity;

//consts
const float c = 0.04;
const vec3 gravity = vec3(0.0,-0.03,0.0);
const float k = 1.0;

void main(void)
{
int N = 64;
vec3 F; 		//Force on the mass
vec3 v = velocity; 	// Final velocity;
vec3 s = vec3(0.0); 	//Displacement step
int index = gl_VertexID;
int ix = index%N;
int iy = index/N;
int connection[4];

if(ix == 0)
{
connection[0] = index;
}
else if(ix == N-1)
{
connection[2] = index;
}
else
{
connection[0] = index-1;
connection[2] = index+1;
}
if(iy == 0)
{
connection[1] = index;
}
else if(iy == N-1)
{
connection[3] = index;
}

else
{
connection[1] = index-N+1;
connection[3] = index+N-1;
}

if(index != 0 && index != N-1)
{
F = gravity- c*velocity;
for(int i=0; i< 4; i++)
{
if(connection[i] != index)
{
vec3 q = texelFetch(tex_position,connection[i]).xyz;
vec3 d = q-position;
float x = length(d);
F += -k*(1-x)*normalize(d);
}
}

s = velocity*t+0.5*F*t*t;
v = velocity + F*t;
}

position_out = position + s;
velocity_out = v;
}```