Calculate specular lighting correctly

Since the lighting calculations are done in object space, the vector
from the object to the viewer also needs to be transformed to object
space.

2 files changed, 9 insertions, 3 deletions

diff --git a/include/private/opengles/gl_context.h b/include/private/opengles/gl_context.h
index 523aed08e15b..67c2dd80681f 100644
--- a/include/private/opengles/gl_context.h
+++ b/include/private/opengles/gl_context.h
@@ -287,6 +287,7 @@ struct light_t {
     vec4_t      normalizedObjPosition;
     vec4_t      spotDir;
     vec4_t      normalizedSpotDir;
+    vec4_t      objViewer;
     GLfixed     spotExp;
     GLfixed     spotCutoff;
     GLfixed     spotCutoffCosine;
diff --git a/opengl/libagl/light.cpp b/opengl/libagl/light.cpp
index 8ae32cc0f0e1..f211bcab3221 100644
--- a/opengl/libagl/light.cpp
+++ b/opengl/libagl/light.cpp
@@ -216,6 +216,8 @@ static inline void light_picker(ogles_context_t* c)
 static inline void validate_light_mvi(ogles_context_t* c)
 {
     uint32_t en = c->lighting.enabledLights;
+    // Vector from object to viewer, in eye coordinates
+    const vec4_t eyeViewer = { 0, 0, 0x1000, 0 };
     while (en) {
         const int i = 31 - gglClz(en);
         en &= ~(1<<i);
@@ -223,6 +225,9 @@ static inline void validate_light_mvi(ogles_context_t* c)
         c->transforms.mvui.point4(&c->transforms.mvui,
                 &l.objPosition, &l.position);
         vnorm3(l.normalizedObjPosition.v, l.objPosition.v);
+        c->transforms.mvui.point4(&c->transforms.mvui,
+                &l.objViewer, &eyeViewer);
+        vnorm3(l.objViewer.v, l.objViewer.v);
     }
 }
 
@@ -379,9 +384,9 @@ void lightVertex(ogles_context_t* c, vertex_t* v)
             // specular
             if (ggl_unlikely(s && l.implicitSpecular.v[3])) {
                 vec4_t h;
-                h.x = d.x;
-                h.y = d.y;
-                h.z = d.z + 0x10000;
+                h.x = d.x + l.objViewer.x;
+                h.y = d.y + l.objViewer.y;
+                h.z = d.z + l.objViewer.z;
                 vnorm3(h.v, h.v);
                 s = dot3(n.v, h.v);
                 s = (s<0) ? (twoSide?(-s):0) : s;