Hi everyone!
I have a trouble with computing directional light in vertex shader. Does anyone can help me out? I so appriciate with your helps.
This is my vertex shader code:

attribute vec3 normal;
attribute vec3 coord3d;
uniform mat4 m;
uniform mat4 v;
uniform mat4 p;
varying vec3 color;
uniform mat3 m3x3_trans_inv;

struct lightSource {
vec4 position;
vec4 diffuse;
};

struct masterial {
vec4 diffuse;
};

lightSource light0 = lightSource(
vec4( 0.0, 1.0, 2.0, 1.0),
vec4( 1.0, 1.0, 1.0, 1.0)
);
masterial obj_mst = masterial(
vec4( 0.9, 0.9, 0.9, 1.0)
);


void main () {
mat4 mvp = p*v*m;
vec3 lightDirection;
if( light0.position.w == 0.0)
{
lightDirection = normalize( vec3( light0.position));
}
else
{
lightDirection = normalize( vec3( light0.position - m * vec4( coord3d, 1.0)));
}

vec3 normalDirection = normalize( m3x3_trans_inv * normal);
vec3 diffuseReflection = vec3( light0.diffuse) * vec3( obj_mst.diffuse) * max( 0.0, dot( normalDirection, lightDirection));
vec4 newPosition = vec4( coord3d, 1.0);
gl_Position = mvp * newPosition;
color = diffuseReflection;
}
But the result is like this:

ht tp://s815.photobucket.com/user/PCthanyeu/media/suzanne.png.html

I try hard to figure out but I can't. Sorry for picture link, because I haven't permission to post full link.