port: fix model lighting

port/fast3d/gfx_pc.cpp

@@ -1014,11 +1014,6 @@ static void gfx_adjust_width_height_for_scale(uint32_t& width, uint32_t& height)
 static void gfx_sp_vertex(size_t n_vertices, size_t dest_index, const Vtx* vertices) {
     SUPPORT_CHECK(n_vertices <= MAX_VERTICES);
 
-    // seems like PD likes to use fog color/alpha without enabling G_FOG
-    const bool use_fog = (rsp.geometry_mode & G_FOG) || 
-        (rdp.other_mode_l >> 30) == G_BL_CLR_FOG ||
-        (rdp.other_mode_l >> 26) == G_BL_A_FOG;
-
     for (size_t i = 0; i < n_vertices; i++, dest_index++) {
         const Vtx* v = &vertices[i];
         struct LoadedVertex* d = &rsp.loaded_vertices[dest_index];
@@ -1138,7 +1133,7 @@ static void gfx_sp_vertex(size_t n_vertices, size_t dest_index, const Vtx* verti
         d->z = z;
         d->w = w;
 
-        if (use_fog) {
+        if (rsp.geometry_mode & G_FOG) {
             if (fabsf(w) < 0.001f) {
                 // To avoid division by zero
                 w = 0.001f;
@@ -1152,7 +1147,7 @@ static void gfx_sp_vertex(size_t n_vertices, size_t dest_index, const Vtx* verti
             float fog_z = z * winv * rsp.fog_mul + rsp.fog_offset;
             d->fog = clampf(fog_z, 0.f, 255.f);
         } else {
-            d->fog = 0;
+            d->fog = rdp.fog_color.a;
         }
 
         d->color.a = vcn->a; // can be required for SHADE_ALPHA even if fog is enabled