void transparentar (GameObject obj)
{
if (obj.renderer != null) {
Vector4 color = obj.renderer.material.color;
obj.renderer.material.shader = Shader.Find ("Transparent/Diffuse");
color [3] = 0.5f;
obj.renderer.material.color = color;
if (!amagats.Contains (obj))
amagats.Add (obj);
}
}