Finished Chapter 6 - Not getting the same image as in book..

With material color (1,0,0) and light_color (1,1,1), (with ray normalized), I am getting the following image: "with-normalize-ray.png": 
If I DON'T normalize the ray, I get:  which I think is more in the spirit of the intended result. For reference, if I do: With light_color (0.1,0.5,0.9), material_color (1,0.2,1), I get:
I'm sure you can imagine what I get if I don't normalize the ray. Please find below the relevant code:

var c = 1;

var c2 = 1; // For debugging after code has completed: c = accumulates for every detected intersection, c2 = accumulates for every instance

// of positive-value hit

function render() {



var shape = new sphere();

sphere.material = new material();

sphere.material.color.x = 1;

sphere.material.color.y = 0.2;

sphere.material.color.z = 1;



//shape.transform = m_multiply(rotation_z(Math.PI / 4, true), scaling(0.5, 1, 1));



var light_position = point(-10,10,-10);

var light_color = colour();





light_color.x = 1;

light_color.y = 1;

light_color.z = 1; // colour() pseudo-constructor only generates default 0,0,0 colour.





var light = new point_light(light_position, light_color /* INTENSITY */);



var world_y;

var world_x;

var pos;



for (var y = 0; y < canvas_pixels; y++) {



world_y = half - (pixel_size * y);



for (var x = 0; x < canvas_pixels; x++) {



world_x = (-half) + (pixel_size * x);



pos = point(world_x, world_y, wall_z);





var r = new ray(ray_origin, normalize(subtract(pos, ray_origin)));





var xs = intersect(shape, r);

if (xs.length>0) {



c++;



var hit_res = hit(xs);



//console.log("intersected ray with sphere!\n");

if (hit_res) {



c2++;



r.origin = normalize(r.origin);

r.direction = normalize(r.direction);



var _point = position(r, hit_res.t);

var _normal = normal_at(hit_res.object, _point);



//var eye = invert(r.direction);

var eye = r.direction;



var _color = lighting(hit_res.object.material, light, _point, eye, _normal);



var col = convert(_color);

//console.log(col + "\n");



write_pixel(x, y, col);



//console.log("writing pixel at " + x + ", " + y + "\n");

}

}

}



}



//debugger;

}


function lighting(_material, _light, _point, eyev, normalv) {



// combine the surface color with the light's color/intensity

var effective_color = multiply(_material.color, _light.intensity);



// find the direction to the light source

var lightv = normalize(subtract(_light.position, _point));



// compute the ambient contribution

var ambient = multiplyInt(effective_color, _material.ambient);



//if (flag1++ < 2)

//debugger;

// ADDED

//ambient = new tuple(0, 0, 0, 0)



/* light_dot_normal represents the cosine of the angle between the

light vector and the normal vector. A negative number means the

light is on the other side of the surface.

*/

var diffuse = colour();

var specular = colour();



var light_dot_normal = dot(lightv, normalv);



if (light_dot_normal < 0) {



diffuse.x = 0;

diffuse.y = 0;

diffuse.z = 0; // black, same as diffuse = colour()



specular.x = 0;

specular.y = 0;

specular.z = 0; // black, same as specular = colour()

}

else {



// compute the diffuse contribution

var res = _material.diffuse * light_dot_normal;

res = multiplyInt(effective_color, res);

diffuse = res;



/* reflect_dot_eye represents the cosine of the angle between the

reflection vector and the eye vector. A negative number means the

light reflects away from the eye.

*/



var neg_lightv = new tuple(-lightv.x, -lightv.y, -lightv.z, VECTOR);

var reflectv = reflect(neg_lightv, normalv);

var reflect_dot_eye = dot(reflectv, eyev);



if (reflect_dot_eye <= 0) {



specular.x = 0;

specular.y = 0;

specular.z = 0; // black

}

else {



// compute the specular contribution

var factor = reflect_dot_eye ** _material.shininess;



var res = _material.specular * factor;

specular = multiplyInt(_light.intensity, res);



//console.log("\tspecular:: r: " + specular.x + ", g: " + specular.y + ", b: " + specular.z + "\n");

// When the above line is uncommented, the component values for specular printed are very low, negligble (<EPSILON)

}

}



var res = colour();



res = add(diffuse, specular);

res = add(ambient, res);



return res;

//return ambient + diffuse + specular;

}

with some global values:

var ray_origin = point(0,0,5);

var wall_z = -10.0;

var wall_size = 7.0;



var canvas_pixels = 550;

var pixel_size = wall_size / canvas_pixels;



var half = wall_size / 2;
Also note, if the colour() pseudo-consructor initialises to (1,1,1), I get the above images: If it initialises to (0,0,0), I get black images....
Please note, in render(), if I swap "var eye = invert(r.direction);
" for "var eye = r.direction;", it makes no difference!!
I have MCI and I am yet to fully internalize the "science" that I've been taught so far in the book, so so far I have been unable to debug the issue...

Thanks!

Lee David O'Dea