In ext. PALETTE.DAT, store log2 of last alpha table index. Handle alpha in classic.

The extended PALETTE.DAT format can now carry a trailing byte, called
'lognumalphatables'. If it is present, the engine assumes that alpha blending
tables are loaded at blend indices 1 to 1<<lognumalphatables and handles
rotatesprite's alpha and spriteext[].alpha accordingly.
The ability to save this new byte is added to engine.lua:savePaletteDat()
and the corresponding convenience functions in shadexfog.lua.

Examples test/screentext.con and test/sprite_access.con are updated for
demonstration purposes.

git-svn-id: https://svn.eduke32.com/eduke32@4426 1a8010ca-5511-0410-912e-c29ae57300e0

polymer/eduke32/build/src/engine.c

@@ -2467,6 +2467,10 @@ char palfadedelta = 0;
 // Internal Engine Functions
 //
 
+// blendtable[1] to blendtable[numalphatabs] are considered to be
+// alpha-blending tables:
+static uint8_t numalphatabs;
+
 static char *blendtable[MAXBLENDTABS];
 void setblendtab(int32_t blend, const char *tab);
 #define getblendtab(blend) (blendtable[blend])
@@ -5609,6 +5613,29 @@ static void drawsprite_opengl(int32_t snum)
     //============================================================================= //POLYMOST ENDS
 }
 
+
+static uint8_t falpha_to_blend(float alpha, int32_t *cstatptr, int32_t transbit1, int32_t transbit2)
+{
+    int32_t blendidx, cstat = *cstatptr;
+
+    if (cstat&transbit1)
+        alpha = 1.0f - (1.0f - alpha) * ((cstat&transbit2) ? 0.33f : 0.66f);
+
+    cstat |= transbit1;
+    cstat &= ~transbit2;
+
+    blendidx = max(1, (int32_t)(alpha * (2*numalphatabs)));  // [1 .. 2*numalphatabs-1]
+    if (blendidx > numalphatabs)
+    {
+        blendidx = 2*numalphatabs - blendidx;
+        cstat |= transbit2;
+    }
+    // blendidx now in [1 .. numalphatabs]
+
+    *cstatptr = cstat;
+    return blendidx;
+}
+
 static void drawsprite_classic(int32_t snum)
 {
     int32_t xoff, yoff, xspan, yspan;
@@ -5627,6 +5654,9 @@ static void drawsprite_classic(int32_t snum)
     int32_t tilenum;
     int32_t cstat = tspr->cstat;
 
+    uint8_t blendidx = tspr->blend;
+    float alpha = spriteext[spritenum].alpha;
+
     if (sec == NULL)
         return;
 
@@ -5635,13 +5665,17 @@ static void drawsprite_classic(int32_t snum)
 
     DO_TILE_ANIM(tspr->picnum, spritenum+32768);
 
-#ifdef USE_OPENGL
+    if (alpha > 0.0f)
     {
-        // hack pending proper alpha implentation
-        // TODO: a real implementation
-        float alpha = spriteext[spritenum].alpha;
+        if (alpha >= 1.0f)
+            return;
 
-        if (alpha >= 0.33f) // if alpha is 0 (which is the default) this structure should only necessitate one comparison
+        if (numalphatabs != 0)
+        {
+            blendidx = falpha_to_blend(alpha, &cstat, 2, 512);
+            tspr->cstat = cstat;
+        }
+        else if (alpha >= 0.33f)
         {
             if ((cstat&2) && alpha >= 0.5f) // this covers the multiplicative aspect used in the Polymodes
                 cstat |= 512;
@@ -5649,17 +5683,11 @@ static void drawsprite_classic(int32_t snum)
             cstat |= 2;
 
             if (alpha >= 0.66f)
-            {
                 cstat |= 512;
 
-                if (alpha >= 1.0f)
-                    return;
-            }
-
             tspr->cstat = cstat;
         }
     }
-#endif
 
     tilenum = tspr->picnum;
 
@@ -5689,7 +5717,7 @@ static void drawsprite_classic(int32_t snum)
     globalshade = tspr->shade;
 
     if (cstat&2)
-        setup_blend(tspr->blend, cstat&512);
+        setup_blend(blendidx, cstat&512);
 
     xoff = picanm[tilenum].xofs + tspr->xoffset;
     yoff = picanm[tilenum].yofs + tspr->yoffset;
@@ -7396,21 +7424,25 @@ static void dorotatesprite(int32_t sx, int32_t sy, int32_t z, int16_t a, int16_t
     if (palookup[dapalnum] == NULL) dapalnum = 0;
     palookupoffs = FP_OFF(palookup[dapalnum]) + (getpalookup(0, dashade)<<8);
 
-    // hack pending proper alpha implentation
-    // TODO: a real implementation
-    if (daalpha > 84) // if alpha is 0 (which is the default) this structure should only necessitate one comparison
+    // Alpha handling
+    if (daalpha > 0)
     {
-        if ((dastat & RS_TRANS1) && daalpha > 127) // this covers the multiplicative aspect used in the Polymodes
-            dastat |= RS_TRANS2;
+        if (daalpha == 255)
+            return;
 
-        dastat |= RS_TRANS1;
-
-        if (daalpha > 168)
+        if (numalphatabs != 0)
         {
-            dastat |= RS_TRANS2;
+            dablend = falpha_to_blend((float)daalpha / 255.0f, &dastat, RS_TRANS1, RS_TRANS2);
+        }
+        else if (daalpha > 84)
+        {
+            if ((dastat & RS_TRANS1) && daalpha > 127) // this covers the multiplicative aspect used in the Polymodes
+                dastat |= RS_TRANS2;
 
-            if (daalpha == 255)
-                return;
+            dastat |= RS_TRANS1;
+
+            if (daalpha > 168)
+                dastat |= RS_TRANS2;
         }
     }
 
@@ -8102,6 +8134,18 @@ static int32_t loadpalette(void)
             }
 
             Bfree(tab);
+
+            // Read log2 of count of alpha blending tables.
+            {
+                uint8_t lognumalphatabs;
+
+                if (kread(fil, &lognumalphatabs, 1) == 1)
+                {
+                    if (!(lognumalphatabs >= 1 && lognumalphatabs <= 7))
+                        return loadpalette_err("invalid lognumalphatabs value, must be in [1 .. 7]");
+                    numalphatabs = 1<<lognumalphatabs;
+                }
+            }
         }
     }
 

polymer/eduke32/source/lunatic/engine.lua

@@ -299,8 +299,9 @@ if (ismapster32) then
         return blendnumtab, blendptrtab
     end
 
-    -- ok, errmsg, nummoreblends = engine.savePaletteDat(filename [, palnum [, blendnum [, moreblends]]])
-    function engine.savePaletteDat(filename, palnum, blendnum, moreblends)
+    -- ok, errmsg, nummoreblends = engine.savePaletteDat(
+    --  filename [, palnum [, blendnum [, moreblends [, lognumalphatabs]]]])
+    function engine.savePaletteDat(filename, palnum, blendnum, moreblends, lognumalphatabs)
         local sht = engine.getshadetab(palnum or 0)
         local tab = engine.getblendtab(blendnum or 0)
 
@@ -313,6 +314,10 @@ if (ismapster32) then
         local blendnumtab, blendptrtab = validate_more_blendtabs(
             moreblends, "blending", C.getblendtab)
 
+        if (not (type(lognumalphatabs)=="number" and lognumalphatabs >= 1 and lognumalphatabs <= 7)) then
+            error("invalid argument #5: must be a number in [1 .. 7]", 2)
+        end
+
         local f, errmsg = io.open(filename, "wb+")
         if (f == nil) then
             return nil, errmsg
@@ -337,6 +342,12 @@ if (ismapster32) then
                     return nil, "failed writing additional blending table"
                 end
             end
+
+            if (lognumalphatabs) then
+                -- XXX: no checking whether these blending tables 1 to
+                -- 1<<lognumalphatabs have been written.
+                f:write(string.char(lognumalphatabs))
+            end
         end
 
         f:close()

polymer/eduke32/source/lunatic/test/screentext.con

@@ -178,6 +178,15 @@ onevent EVENT_DISPLAYREST
     xorvar f TEXT_UPPERCASE
     state increment_line
 
+    // Calculate periodically cycling alpha value
+    setvarvar temp totalclock
+    shiftvarl temp 2
+
+    sin alpha temp   // alpha is now in [-2^14 .. 2^14]
+    shiftvarr alpha 7  // [-2^7 .. 2^7]
+    addvar alpha 128  // [0 .. 256]
+    ifvarg alpha 255 setvar alpha 255
+
     // divider line
     rotatespritea 240 65 32768 512 WINDOWBORDER1 0 2 0 85 x1 y1 x2 y2
 

polymer/eduke32/source/lunatic/test/shadexfog.lua

@@ -269,8 +269,9 @@ end
 
 if (gv.LUNATIC_CLIENT == gv.LUNATIC_CLIENT_MAPSTER32) then
     -- Wrapper around engine.savePaletteDat() that errors on unexpected events.
-    function shadexfog.save(filename, palnum, blendnum, moreblends)
-        local ok, errmsg, nummoreblends = engine.savePaletteDat(filename, palnum, blendnum, moreblends)
+    function shadexfog.save(filename, palnum, blendnum, moreblends, lognumalphatabs)
+        local ok, errmsg, nummoreblends = engine.savePaletteDat(
+            filename, palnum, blendnum, moreblends, lognumalphatabs)
         if (not ok) then
             error(errmsg)
         end
@@ -730,20 +731,31 @@ engine.registerMenuFunc(
             end
         end
 
-        shadexfog.save(filename, palnum, blendnum, moreblends)
+        local lognumalphatabs
+        if (#moreblends > 0) then
+            lognumalphatabs = getnumber16("log2 of last alpha blending table index (1-7, 0: none): ", 0, 7)
+            if (lognumalphatabs < 0) then return end
+            if (lognumalphatabs == 0) then lognumalphatabs = nil end
+        end
+
+        shadexfog.save(filename, palnum, blendnum, moreblends, lognumalphatabs)
     end,
 
 formatHelp
 [[
-<shadexfog.save(filename, palnum, blendnum, moreblends)>
-<______________________________________________________>
+<shadexfog.save(filename, palnum, blendnum, moreblends, lognumalpha)>
+<___________________________________________________________________>
 
 Writes out a full PALETTE.DAT-formatted file named <filename> with the
 base shade table numbered <palnum> and the base translucency table
 numbered <blendnum>.
 
 Finally, you are asked to specify additional blending tables that can
-be stored in EDuke32's extended PALETTE.DAT format.
+be stored in EDuke32's extended PALETTE.DAT format. If one or more
+additional blending table is specified, you are also queried for the
+log2 of the last alpha blending table index, <lognumalpha>. Since alpha
+blending tables are assumed to be set up at indices 1 to 2^<lognumalpha>,
+it is also the log2 of their total count.
 ]]
 )
 

polymer/eduke32/source/lunatic/test/sprite_access.con

@@ -80,6 +80,8 @@ define NUMALPHATABS 128
 define C1 0  //must be log2(128/NUMALPHATABS)
 define C2 257  // must be 2*NUMALPHATABS+1
 
+define ALPHA_TABS_BY_EDUKE32 1  // assume alpha->blend handling by EDuke32
+
 onevent EVENT_ANIMATESPRITES
     setvarvar tmp totalclock
     shiftvarl tmp 2
@@ -89,6 +91,15 @@ onevent EVENT_ANIMATESPRITES
     addvar alpha 128  // [0 .. 256]
     shiftvarr alpha C1  // [0 .. 2*NUMALPHATABS]
 
+    ifvarn ALPHA_TABS_BY_EDUKE32 0
+    {
+        subvar alpha 1
+        ifvarl alpha 0 setvar alpha 0
+        setactor[THISACTOR].alpha alpha
+
+        break
+    }
+
     ifvare alpha 0
     {
         // clear translucent bits, 0xfdfe == 0xffff-(1+512)
@@ -103,7 +114,7 @@ onevent EVENT_ANIMATESPRITES
         settspr[THISACTOR].tsprcstat tmp
 
         // Assume blending tables [1 .. NUMALPHATABS] are installed, like
-        // generated by shadexfog.lua:create_128_trans(1, NUMALPHATABS).
+        // generated by shadexfog.lua:create_alpha_trans(1, NUMALPHATABS).
         ifvarg alpha NUMALPHATABS
         {
             setvarvar tmp C2