perf(engine): eliminate idiv in floor and ceiling render using tableInvDelta3D and tableStepRatio3D LUTs

src_graphics/hall_data.inc

@@ -25,6 +25,9 @@ RenderPatrons3D PROTO
 ResolveWorldSurface3D PROTO :DWORD
 include src_graphics\hall_layout.inc
 .data
+ALIGN 4
+tableInvDelta3D   dd 241 dup(0)
+tableStepRatio3D  dd 241 dup(0)
 hallSign3D AnimPack3D <>
 hallSignPath3D db "assets\animations\hall\sign.bin",0
 hallCityDetail3D AnimPack3D <>

src_graphics/hall_scene.inc

@@ -27,9 +27,18 @@ hall_plane_floor:
     mov ebx, floorTexture3D
     mov material, ebx
 hall_plane_distance:
-    imul eax, SCREEN_H
+    cmp ecx, 240
-    cdq
+    jbe @F
-    idiv ecx
+    mov ecx, 240
+@@:
+    cmp ecx, 1
+    jae @F
+    mov ecx, 1
+@@:
+    push eax
+    mov edx, [tableInvDelta3D + ecx*4]
+    imul edx
+    shrd eax, edx, 16
     mov distance, eax
     shr eax, 14
     neg eax
@@ -46,20 +55,18 @@ hall_plane_distance:
     shr eax, 3
     mov shade, eax
 @@:
-    mov eax, playerPlaneX
+    pop eax
-    shl eax, 1
+    mov edx, [tableStepRatio3D + ecx*4]
-    imul distance
+    imul edx
+    shrd eax, edx, 16
+    mov ebx, eax
+    mov eax, playerPlaneX
+    imul ebx
     shrd eax, edx, 16
-    cdq
-    mov ecx, SCREEN_W
-    idiv ecx
     mov sx, eax
     mov eax, playerPlaneY
-    shl eax, 1
+    imul ebx
-    imul distance
     shrd eax, edx, 16
-    cdq
-    idiv ecx
     mov sy, eax
     mov eax, playerDirX
     sub eax, playerPlaneX
@@ -278,6 +285,22 @@ InitHall3D PROC uses esi edi
     mov floorTexture3D, 100
     mov casinoSprites[14*SIZEOF SpriteObject].interactId, 0
     mov patronClock3D, 0
+    ; Precalculate floor & ceiling distance / step LUTs (no division at runtime)
+    mov ecx, 1
+init_plane_lut:
+    cmp ecx, 241
+    jge init_plane_done
+    mov eax, SCREEN_H * FP_1
+    xor edx, edx
+    div ecx
+    mov [tableInvDelta3D + ecx*4], eax
+    mov eax, 98304
+    xor edx, edx
+    div ecx
+    mov [tableStepRatio3D + ecx*4], eax
+    inc ecx
+    jmp init_plane_lut
+init_plane_done:
     call InitCasinoNpcMind
     call InitNpcLife3D
     ret