Fix directional lights

The interpretation of lightDir was different for point and directional
lights: it was surface-to-light for point lights, but light-to-surface
for directional.

Fix this by getting rid of lightDir and instead setting up s (surface-to-light)
correctly.

Change-Id: I0bc6947dc94622d7a95f55fd65b3baf43fd11528
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

2 files changed, 33 insertions, 30 deletions

diff --git a/src/render/shaders/es2/light.inc.frag b/src/render/shaders/es2/light.inc.frag
index 516d701f1..a42e573a4 100644
--- a/src/render/shaders/es2/light.inc.frag
+++ b/src/render/shaders/es2/light.inc.frag
@@ -20,17 +20,17 @@ void adsModelNormalMapped(const in FP vec3 vpos, const in FP vec3 vnormal, const
     FP vec3 n = normalize( vnormal );
 
     // TODO dynamic indexing may not be supported with GLSL 1.00 so take only the first light into account
-    FP vec3 lightDir = lights[0].direction;
+    FP vec3 s = -lights[0].direction;
     FP float att = 1.0;
-    if (length( lightDir ) == 0.0) {
-        lightDir = lights[0].position - vpos;
+    if (length( s ) == 0.0) {
+        s = lights[0].position - vpos;
         if (length( lights[0].attenuation ) != 0.0) {
-            FP float dist = length(lightDir);
+            FP float dist = length(s);
             att = 1.0 / (lights[0].attenuation.x + lights[0].attenuation.y * dist + lights[0].attenuation.z * dist * dist);
         }
     }
 
-    FP vec3 s = normalize( tangentMatrix * lightDir );
+    s = normalize( tangentMatrix * s );
     FP float diffuse = max( dot( s, n ), 0.0 );
 
     FP float specular = 0.0;
@@ -54,17 +54,17 @@ void adsModel(const in FP vec3 vpos, const in FP vec3 vnormal, const in FP vec3
     FP vec3 n = normalize( vnormal );
 
     // TODO dynamic indexing may not be supported with GLSL 1.00 so take only the first light into account
-    FP vec3 lightDir = lights[0].direction;
+    FP vec3 s = -lights[0].direction;
     FP float att = 1.0;
-    if (length( lightDir ) == 0.0) {
-        lightDir = lights[0].position - vpos;
+    if (length( s ) == 0.0) {
+        s = lights[0].position - vpos;
         if (length( lights[0].attenuation ) != 0.0) {
-            FP float dist = length(lightDir);
+            FP float dist = length(s);
             att = 1.0 / (lights[0].attenuation.x + lights[0].attenuation.y * dist + lights[0].attenuation.z * dist * dist);
         }
     }
 
-    FP vec3 s = normalize( lightDir );
+    s = normalize( s );
     FP float diffuse = max( dot( s, n ), 0.0 );
 
     FP float specular = 0.0;
@@ -86,17 +86,17 @@ void adModel(const in FP vec3 vpos, const in FP vec3 vnormal, out FP vec3 diffus
     FP vec3 n = normalize( vnormal );
 
     // TODO dynamic indexing may not be supported with GLSL 1.00 so take only the first light into account
-    FP vec3 lightDir = lights[0].direction;
+    FP vec3 s = -lights[0].direction;
     FP float att = 1.0;
-    if (length( lightDir ) == 0.0) {
-        lightDir = lights[0].position - vpos;
+    if (length( s ) == 0.0) {
+        s = lights[0].position - vpos;
         if (length( lights[0].attenuation ) != 0.0) {
-            FP float dist = length(lightDir);
+            FP float dist = length(s);
             att = 1.0 / (lights[0].attenuation.x + lights[0].attenuation.y * dist + lights[0].attenuation.z * dist * dist);
         }
     }
 
-    FP vec3 s = normalize( lightDir );
+    s = normalize( s );
     FP float diffuse = max( dot( s, n ), 0.0 );
 
     diffuseColor += att * lights[0].intensity * diffuse * lights[0].color;
diff --git a/src/render/shaders/gl3/light.inc.frag b/src/render/shaders/gl3/light.inc.frag
index 6d4b8b68f..e9dc021c4 100644
--- a/src/render/shaders/gl3/light.inc.frag
+++ b/src/render/shaders/gl3/light.inc.frag
@@ -20,18 +20,19 @@ void adsModelNormalMapped(const in vec3 vpos, const in vec3 vnormal, const in ve
     vec3 n = normalize( vnormal );
 
     int i;
+    vec3 s;
     for (i = 0; i < lightCount; ++i) {
-        vec3 lightDir = lights[i].direction;
+        s = -lights[i].direction;
         float att = 1.0;
-        if (length( lightDir ) == 0.0) {
-            lightDir = lights[i].position - vpos;
+        if (length( s ) == 0.0) {
+            s = lights[i].position - vpos;
             if (length( lights[i].attenuation ) != 0.0) {
-                float dist = length(lightDir);
+                float dist = length(s);
                 att = 1.0 / (lights[i].attenuation.x + lights[i].attenuation.y * dist + lights[i].attenuation.z * dist * dist);
             }
         }
 
-        vec3 s = normalize( tangentMatrix * lightDir );
+        s = normalize( tangentMatrix * s );
         float diffuse = max( dot( s, n ), 0.0 );
 
         float specular = 0.0;
@@ -56,18 +57,19 @@ void adsModel(const in vec3 vpos, const in vec3 vnormal, const in vec3 eye, cons
     vec3 n = normalize( vnormal );
 
     int i;
+    vec3 s;
     for (i = 0; i < lightCount; ++i) {
-        vec3 lightDir = lights[i].direction;
+        s = -lights[i].direction;
         float att = 1.0;
-        if (length( lightDir ) == 0.0) {
-            lightDir = lights[i].position - vpos;
+        if (length( s ) == 0.0) {
+            s = lights[i].position - vpos;
             if (length( lights[i].attenuation ) != 0.0) {
-                float dist = length(lightDir);
+                float dist = length(s);
                 att = 1.0 / (lights[i].attenuation.x + lights[i].attenuation.y * dist + lights[i].attenuation.z * dist * dist);
             }
         }
 
-        vec3 s = normalize( lightDir );
+        s = normalize( s );
         float diffuse = max( dot( s, n ), 0.0 );
 
         float specular = 0.0;
@@ -90,18 +92,19 @@ void adModel(const in vec3 vpos, const in vec3 vnormal, out vec3 diffuseColor)
     vec3 n = normalize( vnormal );
 
     int i;
+    vec3 s;
     for (i = 0; i < lightCount; ++i) {
-        vec3 lightDir = lights[i].direction;
+        s = -lights[i].direction;
         float att = 1.0;
-        if (length( lightDir ) == 0.0) {
-            lightDir = lights[i].position - vpos;
+        if (length( s ) == 0.0) {
+            s = lights[i].position - vpos;
             if (length( lights[i].attenuation ) != 0.0) {
-                float dist = length(lightDir);
+                float dist = length(s);
                 att = 1.0 / (lights[i].attenuation.x + lights[i].attenuation.y * dist + lights[i].attenuation.z * dist * dist);
             }
         }
 
-        vec3 s = normalize( lightDir );
+        s = normalize( s );
         float diffuse = max( dot( s, n ), 0.0 );
 
         diffuseColor += att * lights[i].intensity * diffuse * lights[i].color;