Here is a mel script i made a while ago to tweak the lighting of my still images. It basically does what you asked for, or more precise, it creates a curve either from mesh faces or a points on a nurbs surface that is the reflection ray of the current cameras view to these points using their normal. Call the procedure with cShowReflectionRay().

Code:

global proc cShowReflectionRay(){
if(`window -exists "cShowReflectionRay"`) deleteUI "cShowReflectionRay";
if(`windowPref -exists "cShowReflectionRay"`) windowPref -remove "cShowReflectionRay";
window -title "show reflection ray" -width 300 -resizeToFitChildren 1 "cShowReflectionRay";
string $mainLayout = `rowColumnLayout -numberOfColumns 1 -cw 1 300`;
separator -style "none" -height 10;
rowColumnLayout -numberOfColumns 3 -cw 1 10 -cw 2 260 -cw 3 10;
text -l "";
string $radioGrp = `radioButtonGrp
-numberOfRadioButtons 2
-labelArray2 "average values" "per component"
-cw 1 129
-select 1`;
text -l "";
setParent $mainLayout;
separator -style "none" -height 7;
rowColumnLayout -numberOfColumns 5 -cw 1 5 -cw 2 97 -cw 3 96 -cw 4 97 -cw 5 5;
text -l "";
button -l "show rays" -command ("cShowReflectionRay_doIt (`radioButtonGrp -q -select \"" + $radioGrp + "\"` - 1);");
button -l "ok" -command ("cShowReflectionRay_doIt (`radioButtonGrp -q -select \"" + $radioGrp + "\"` - 1)");
button -l "cancel" -command ("deleteUI \"cShowReflectionRay\"");
setParent $mainLayout;
separator -style "none" -height 5;
showWindow "cShowReflectionRay";
};
global proc cShowReflectionRay_doIt(int $showRayPerComponent)
{
string $sel[] = `ls -fl -sl`;
string $activePanel = `getPanel -withFocus`;
string $currentCam = `modelPanel -q -camera $activePanel`;
string $camTransform[] = {};
if(`nodeType $currentCam` == "camera")
{
$camTransform = `listRelatives -parent -f $currentCam`;
}
else $camTransform = {$currentCam};
vector $camPos = `xform -q -ws -t $camTransform[0]`;
vector $pList[] = {};
vector $nList[] = {};
for($i=0;$i<`size $sel`;$i++)
{
string $shape[] = `ls -long -o $sel[0]`;
string $component[] = {$sel[$i]};
vector $p, $n;
if(`nodeType $shape[0]` == "nurbsSurface")
{
tokenize $component[0] "[]" $component;
float $uv[] = {(float($component[1])),(float($component[2]))};
$p = `pointOnSurface -u $uv[0] -v $uv[1] -p $shape[0]`;
$n = `pointOnSurface -u $uv[0] -v $uv[1] -nn $shape[0]`;
}
else if(`nodeType $shape[0]` == "mesh")
{
string $fv[] = `polyListComponentConversion -ff -tvf $component[0]`;
$fv = `filterExpand -sm 70 -ex true $fv`;
if(`size $fv` < 3){
print($component[0] + ": invalid face, skipped\n");
continue;
};
float $tmp[] = {};
float $averagePos[] = {};
for($k=0;$k<`size $fv`;$k++){
string $vertex[] = `polyListComponentConversion -fvf -tv $fv[$k]`;
float $pos[] = `xform -q -ws -t $vertex[0]`;
$tmp[`size $tmp`] = $pos[0];
$tmp[`size $tmp`] = $pos[1];
$tmp[`size $tmp`] = $pos[2];
};
vector $v1 = <<($tmp[3] - $tmp[0]),($tmp[4] - $tmp[1]),($tmp[5] - $tmp[2])>>;
vector $v2 = <<($tmp[6] - $tmp[0]),($tmp[7] - $tmp[1]),($tmp[8] - $tmp[2])>>;
float $averagePos[] = {};
for($k=0;$k<`size $fv`;$k++){
$averagePos[0] = $averagePos[0] + $tmp[$k * 3];
$averagePos[1] = $averagePos[1] + $tmp[$k * 3 + 1];
$averagePos[2] = $averagePos[2] + $tmp[$k * 3 + 2];
};
$averagePos = {($averagePos[0] / `size $fv`),($averagePos[1] / `size $fv`),($averagePos[2] / `size $fv`)};
$p = <<$averagePos[0],$averagePos[1],$averagePos[2]>>;
$n = unit(`cross $v1 $v2`);
}
else
return;
if($showRayPerComponent == 1){
vector $camToPOS = $camPos - $p;
float $length_1 = mag($camToPOS);
float $length_2 = sind(90 - `rad_to_deg (angle($n, $camToPOS))`) * $length_1;
vector $mPoint = $p + $n * $length_2;
vector $camToMPoint = $mPoint - $camPos;
vector $finalPoint = $mPoint + $camToMPoint;
string $curve = `curve -d 1 -p ($p.x) ($p.y) ($p.z) -p ($finalPoint.x) ($finalPoint.y) ($finalPoint.z)`;
xform -piv ($p.x) ($p.y) ($p.z) $curve;
}else{
$pList[`size $pList`] = $p;
$nList[`size $nList`] = $n;
};
};
if($showRayPerComponent == 0){
float $p[], $n[];
int $numComponents = `size $pList`;
for($i=0;$i<`size $pList`;$i++){
vector $tmp = $pList[$i];
$p[0] = $p[0] + ($tmp.x) / $numComponents;
$p[1] = $p[1] + ($tmp.y) / $numComponents;
$p[2] = $p[2] + ($tmp.z) / $numComponents;
$tmp = $nList[$i];
$n[0] = $n[0] + ($tmp.x) / $numComponents;
$n[1] = $n[1] + ($tmp.y) / $numComponents;
$n[2] = $n[2] + ($tmp.z) / $numComponents;
};
vector $camToPOS = $camPos - <<$p[0],$p[1],$p[2]>>;
float $length_1 = mag($camToPOS);
float $length_2 = sind(90 - `rad_to_deg (angle(<<$n[0],$n[1],$n[2]>>, $camToPOS))`) * $length_1;
vector $mPoint = <<$p[0],$p[1],$p[2]>> + <<$n[0],$n[1],$n[2]>> * $length_2;
vector $camToMPoint = $mPoint - $camPos;
vector $finalPoint = $mPoint + $camToMPoint;
string $curve = `curve -d 1 -p $p[0] $p[1] $p[2] -p ($finalPoint.x) ($finalPoint.y) ($finalPoint.z)`;
xform -piv $p[0] $p[1] $p[2] $curve;
};
};