glsl - Shadow not rendered correctly -

shadow map http://i59.tinypic.com/16k5bv4.png

i trying create shadow using shadow maps. believe shadow map rendered well.

it seems sphere's shadow not in correct place, how go fixing that? why there black ring around sphere , how eliminate it?

in shadow map vertex shader

gl_position = u_depthmatrix * worldcoord; 

in shadow map fragment shader

fragmentdepth =  gl_fragcoord.z; 

vs.glsl

uniform mat4 u_model; uniform mat4 u_view; uniform mat4 u_persp; uniform mat4 u_invtrans; uniform vec3 u_lightcolor; uniform vec3 u_lightdirection; uniform vec3 u_eyepos; uniform mat4 u_depthbiasmatrix;  in vec3 position; in vec3 normal; in vec2 texcoord;   out vec3 v_normal; out vec2 v_texcoord; out vec3 v_position; out vec3 v_positionmc;  out vec4 shadowcoord;  void main(void) {     v_normal = (u_invtrans*vec4(normal,0.0)).xyz;     vec4 world = u_model * vec4(position, 1.0);     vec4 cameracoord = u_view * world;     v_position = cameracoord.xyz;     shadowcoord = u_depthbiasmatrix * world;     gl_position = u_persp * cameracoord; } 

fs.glsl

    uniform sampler2d shadowmap; uniform vec3 u_lightcolor; uniform vec3 u_lightdirection; uniform vec3 u_eyepos; uniform vec3 u_ka; uniform vec3 u_kd; uniform vec3 u_ks;   in vec3 v_normal;    in vec2 v_texcoord; in vec3 v_position;            //coordinate of vertex in camera coordinate system  in vec4 shadowcoord;  void main(void) {     vec3 v_normal1 = normalize(v_normal);     //diffuse lighting     vec3 diff = normalize(u_lightdirection - v_position);     float diffuse = max(dot(diff , v_normal1) , 0);     vec3 diffusecolor = diffuse * u_kd * u_lightcolor;      //specular lighting     vec3 v = normalize(vec3(u_eyepos - v_position));     vec3 h = normalize(diff + v);     float sl = pow(max(dot(h, v_normal1) , 0.0),  50);     if ( diffuse <= 0 ) sl = 0;      vec3 specularcolor = sl * u_ks * u_lightcolor;      vec3 v_color;     v_color =  u_ka + diffusecolor + specularcolor ;      //shadow part     vec3 shadowcoord3;     float shadowfactor = 1.0;     if(shadowcoord.w > 0 )     {         shadowcoord3 = shadowcoord.xyz / shadowcoord.w ;          if ( texture2d( shadowmap, shadowcoord3.xy ).z  <  shadowcoord3.z)         {             shadowfactor = 0.2;         }     }     gl_fragcolor = shadowfactor * vec4(v_color , 1);   }