Light direction not being calculated correctly

Question

I'm trying to implement deferred lighting in my game, and have run into an issue with normals.

The image above shows the lighting being applied to a tile map. The yellow shade represents the direction of the light at that pixel. The character has a green normal so when he is below the light as he is in the screenshot, he doesn't get lit. I was working through the problem of the character always being lit, and it seems to be because the light direction isn't calcualted correctly. I expect the light direction color to be a rainbow of colors, however the yellow means that the light is always point down X and Y axis instead of radiating out in a circle. I'm certain that worldPos is coming out correct because the diffuse/normal colors are being displayed correctly.

Fragment shader for the light:

#version 330

uniform sampler2D diffuseTexture;
uniform sampler2D normalsTexture;
in vec2 TexCoords;

out vec4 outColor;

void main(void) {
    vec2 resolution = vec2(200, 200);
    float distance = length(vec3((TexCoords*resolution) - (resolution / 2),
                                0.0));
    float constantAttenuation = 1.0;
    float linearAttenuation = 0.1;
    float quadradicAttenuation = 0.01;

    float attenuation = 1.0 / (constantAttenuation +
    (linearAttenuation*distance) + (quadradicAttenuation*distance*distance));

    vec3 worldPos = gl_FragCoord.xyz / vec3(1024, 768, 1.0);
    vec3 lightDir = normalize(vec3(50,50,10) - worldPos);

    float diffuseFact = dot(normalize(texture2D(normalsTexture, worldPos.xy).rgb), lightDir);

    vec4 diffuse = vec4(0.0);

    if(diffuseFact > 0.0) {
        diffuse = vec4(texture2D(normalsTexture, worldPos.xy).rgb, 1.0);
        diffuse = diffuse * diffuseFact * 10;
    }

    outColor = vec4(lightDir, 0.5) + (diffuse*attenuation);
}

Answer 1

At rcapote's suggestion, here's my answer as an answer:

Ah, so your light rectangle is 200 by 200, and distance is from the center of that? In that case, I believe that lightDir should be also be based on the center of that rectangle and not world coordinates. Probably lightDir = vec3(0.5, 0.5, 0.1) - vec3(TexCoords, 0.0).

Glad I could help!