Ticket #8045: gfx.cpp.unkroomfunc3.diff

scummvm\scumm\gfx.

@@ -2584 +2584 @@
         }
 }
 
-void Scumm::unkRoomFunc3(int unk1, int unk2, int rfact, int gfact, int bfact)
+void Scumm::unkRoomFunc3(int palstart, int palend, int rfact, int gfact, int bfact)
 {
-        byte *pal = _currentPalette;
+        byte *basepal = getPalettePtr();
+        byte *pal = basepal;
+        byte *compareptr;
         byte *table = _shadowPalette;
         int i;
 
-        warning("unkRoomFunc3(%d,%d,%d,%d,%d): not fully implemented", unk1, unk2, rfact, gfact, bfact);
-
-        // TODO - correctly implement this function (see also patch #588501)
-        //
-        // Some "typical" examples of how this function is being invoked in real life:
-        //
-        // 1)
-        // unkRoomFunc3(16, 255, 200, 200, 200)
-        //
-        // FOA: Sets up the colors for the boat and submarine shadows in the
-        // diving scene. Are the shadows too light? Maybe unk1 is used to
-        // darken the colors?
-        //
-        // 2)
-        // unkRoomFunc3(0, 255, 700, 700, 700)
-        //
-        // FOA: Sets up the colors for the subway car headlight when it first
-        // goes on. This seems to work ok.
-        //
-        // 3)
-        // unkRoomFunc3(160, 191, 300, 300, 300)
-        // unkRoomFunc3(160, 191, 289, 289, 289)
-        //     ...
-        // unkRoomFunc3(160, 191, 14, 14, 14)
-        // unkRoomFunc3(160, 191, 3, 3, 3)
-        //
-        // 4)
-        // FOA: Sets up the colors for the subway car headlight for the later
-        // half of the trip, where it fades out. This currently doesn't work
-        // at all. The colors are too dark to be brightened. At first I thought
-        // unk1 and unk2 were used to tell which color interval to manipulate,
-        // but as far as I can tell the colors 160-191 aren't used at all to
-        // draw the light, that can't be it. Apparently unk1 and/or unk2 are
-        // used to brighten the colors.
-        //
-        // 5)
-        // unkRoomFunc3(16,255,500,500,500)
+        // This is a correction of the patch supplied for BUG #588501.
+        // It has been tested in four rooms where unkRoomFunc3 is used.
         //
-        // FOA: Used in the Inner Sanctum after you activated the machine using the
-        // stone discs (briefly before the Nazis arrive). No idea at all if it is
-        // right here; also note that palManipulateInit() is called at the same time.
-        //
-        //
-        
+        // 1) FOA Room 53: subway departing Knossos for Atlantis.
+        // 2) FOA Room 48: subway crashing into the Atlantis entance area
+        // 3) FOA Room 82: boat/sub shadows while diving near Thera
+        // 4) FOA Room 23: the big machine room inside Atlantis
+        //
+        // The implementation behaves well in all tests.
+        // Pixel comparisons show that the resulting palette entries being
+        // derived from the shadow palette generated here occassionally differ
+        // slightly from the ones derived in the LEC executable.
+        // Not sure yet why, but the differences are VERY minor.
+        //
+        // Once again, there seems to be no explanation for why this function
+        // is called from within Room 23 (the big machine), as it has no shadow
+        // effects and thus doesn't result in any visual differences.
+
         for (i = 0; i <= 255; i++) {
                 int r = (int) (*pal++ * rfact) >> 8;
                 int g = (int) (*pal++ * gfact) >> 8;
                 int b = (int) (*pal++ * bfact) >> 8;
 
-                *table++ = remapPaletteColor(r, g, b, (uint) -1);
+                // The following functionality is similar to remapPaletteColor, except
+                // 1) we have to work off the original CLUT rather than the current palette, and
+                // 2) the target shadow palette entries must be bounded to the upper and lower
+                //    bounds provided by the opcode. (This becomes significant in Room 48, but
+                //    is not an issue in all other known case studies.)
+                int j;
+                int ar, ag, ab;
+                uint sum, diff, bestsum, bestitem = 0;
+                compareptr = basepal + palstart * 3;
+
+                if (r > 255)
+                        r = 255;
+                if (g > 255)
+                        g = 255;
+                if (b > 255)
+                        b = 255;
+
+                bestsum = (uint) - 1;
+
+                r &= ~3;
+                g &= ~3;
+                b &= ~3;
+
+                for (j = palstart; j <= palend; j++, compareptr += 3) {
+                        ar = compareptr[0] & ~3;
+                        ag = compareptr[1] & ~3;
+                        ab = compareptr[2] & ~3;
+                        if (ar == r && ag == g && ab == b) {
+                                bestitem = j;
+                                break;
+                        }
+
+                        diff = ar - r;
+                        sum = diff * diff * 3;
+                        diff = ag - g;
+                        sum += diff * diff * 6;
+                        diff = ab - b;
+                        sum += diff * diff * 2;
+
+                        if (sum < bestsum) {
+                                bestsum = sum;
+                                bestitem = j;
+                        }
+                }
+                *table++ = bestitem;
         }
 }