hi. i’m a newbie of opengl and GLSL. i’m writing a phong shader but it don’t work. Light type would be directional. Can you segnale me where i’m wrong, please? Thanks
(sorry for my bad english 
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vertex:
varying vec3 normal,lightDir;
varying vec3 vertexPosition;
uniform vec3 ucLightDir;
uniform vec4 ucLightAmbient,ucLightDiffuse,ucLightSpecular;
void main() {
normal = normalize(gl_NormalMatrix * gl_Normal);
vertexPosition = (gl_ModelViewProjectionMatrix * gl_Vertex).xyz;
lightDir=ucLightDir;
gl_TexCoord[0] = gl_MultiTexCoord0;
//transform vertices
gl_Position = ftransform();
}
Fragment:
uniform gl_LightSourceParameters gl_LightSource[gl_MaxLights];
uniform gl_LightModelParameters gl_LightModel;
varying vec3 normal;
varying vec3 lightDir;
varying vec3 vertexPosition;
uniform vec4 ucLightAmbient,ucLightDiffuse,ucLightSpecular;
uniform sampler2D tex;
//fragment shader
void main()
{
vec4 ambient,diffuse,specular;
//normalizing
vec3 nNormal = normalize ( normal );
vec3 nLightDir = normalize ( lightDir );
//DIFFUSE TERM
float lambertTerm = dot(nNormal,nLightDir);
//clamp 0-1 range
lambertTerm = max(lambertTerm,0.0);
diffuse = gl_FrontMaterial.diffuse * ucLightDiffuse * lambertTerm;
//AMBIENT TERM
vec4 lightAmbient = ucLightAmbient * gl_FrontMaterial.ambient;
vec4 globalAmbient = gl_LightModel.ambient * gl_FrontMaterial.ambient;
ambient = lightAmbient + globalAmbient;
//SPECULAR TERM
if(lambertTerm>0.0) {
vec3 eye = normalize (vertexPosition);
vec3 reflectionVec = reflect(-nLightDir, normal);
reflectionVec = normalize(reflectionVec);
vec3 halfVector = vec3(eye+nLightDir);
float RdotE = max( dot (nNormal,halfVector) , 0.0);
specular = gl_FrontMaterial.specular * ucLightSpecular * pow( RdotE , gl_FrontMaterial.shininess);
} //if(cosine>0.0) {
vec4 texel = texture2D(tex,gl_TexCoord[0].xy);
//set color
gl_FragColor = (diffuse + ambient + specular ) ;
}
).