From 86fc9d3ddadb1512fddf34dc74e0f2fefd510e25 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miloslav=20=C4=8C=C3=AD=C5=BE?= <tastyfish@seznam.cz>
Date: Wed, 12 Sep 2018 12:01:16 +0200
Subject: [PATCH] Optimize sprites even more

---
 demo1.cpp   |  8 +++++---
 general.hpp | 15 +++++++++++----
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/demo1.cpp b/demo1.cpp
index 7206ae9..a2a1fea 100644
--- a/demo1.cpp
+++ b/demo1.cpp
@@ -756,9 +756,12 @@ void draw()
     PixelInfo pos = mapToScreen(sprites[i].mPosition,sprites[i].mHeight,player.mCamera);
 
     if (pos.depth > 0)
-      drawSprite(sprites[i].mImage,pos.position.x * SUBSAMPLE,pos.position.y,
-                 pos.depth,perspectiveScale(sprites[i].mPixelSize,pos.depth));
+      drawSpriteSquare(sprites[i].mImage,pos.position.x * SUBSAMPLE,
+        pos.position.y, pos.depth,
+        perspectiveScale(sprites[i].mPixelSize,pos.depth));
 
+    /* trick: sort the sprites by distance with bubble sort as we draw - the
+       order will be correct in a few frames */
     if (i != 0 && pos.depth > previousDepth)
     {
       Sprite tmp = sprites[i];
@@ -791,7 +794,6 @@ int main()
   initGeneral();
 
   player.setPositionSquare(6,4);
-player.setPosition(7119,14343,5120,566);
 
   sprites[0] = Sprite(sprite1,10,5,1,100);
   sprites[1] = Sprite(sprite1,14,5,1,100);
diff --git a/general.hpp b/general.hpp
index fac169a..4d6c7c9 100644
--- a/general.hpp
+++ b/general.hpp
@@ -177,9 +177,14 @@ inline uint8_t sampleImage(const unsigned char *image, Unit x, Unit y)
   return image[2 + index];
 }
 
-void inline drawSprite(const unsigned char *sprite, int16_t x, int16_t y, Unit depth, int16_t size)
+/**
+  Draws a scaled sprite on screen in an optimized way. The sprite has to be
+  square in resolution.
+*/
+void inline drawSpriteSquare(const unsigned char *sprite, int16_t x, int16_t y, Unit depth, int16_t size)
 {
-  if (size < 0 || size > 200) // let's not mess up with the incoming array
+  if (size < 0 || size > 200 || // let's not mess up with the incoming array
+      sprite[0] != sprite[1])   // only draw square sprites
     return;
 
   int16_t samplingIndices[size];
@@ -187,7 +192,7 @@ void inline drawSprite(const unsigned char *sprite, int16_t x, int16_t y, Unit d
   // optimization: precompute the indices
 
   for (Unit i = 0; i < size; ++i)
-    samplingIndices[i] = (i * UNITS_PER_SQUARE) / size;
+    samplingIndices[i] = (i * sprite[0]) / size;
 
   x -= size / 2;
   y -= size / 2;
@@ -206,9 +211,11 @@ void inline drawSprite(const unsigned char *sprite, int16_t x, int16_t y, Unit d
     if (zBuffer[xPos / SUBSAMPLE] <= depth)
       continue;
 
+    int16_t columnLocation = 2 + samplingIndices[i] * sprite[0];
+
     for (Unit j = max(-1 * y,0); j < jTo; ++j)
     {
-      c = sampleImage(sprite,samplingIndices[i],samplingIndices[j]); 
+      c = sprite[columnLocation + samplingIndices[j]];
      
       if (c != TRANSPARENT_COLOR)
         pokitto.display.drawPixel(xPos,y + j,c);