color index generation for rasterizer

README.md

@@ -6,9 +6,11 @@ This is (very) loosely based on David's 3D soft engine in C#/JS: https://www.dav
 
 Engine blueprint: a stripped-down version of [https://github.com/wgroeneveld/gba-sprite-engine/](https://github.com/wgroeneveld/gba-sprite-engine/) combined with more _tonc_ library functions. 
 
-#### Show me the money
+### Show me the money!
 
-Sure thing. **Demo 1**: without wires
+Sure thing. 
+
+#### **Demo 1**: without wires
 
 ![design](https://github.com/wgroeneveld/gba-bitmap-engine/blob/master/img/wireless.gif?raw=true)
 
@@ -17,7 +19,7 @@ You 'should' see a cube forming based on 8 vertices. It's a simple example to sh
 
 60 FPS. Yay.
 
-**Demo 1b**: with wires
+#### **Demo 1b**: with wires
 
 ![design](https://github.com/wgroeneveld/gba-bitmap-engine/blob/master/img/wired.gif?raw=true)
 
@@ -28,7 +30,11 @@ MODE4's weird byte write problems are causing trouble. Time to consult _tonc_ an
 
 30 FPS, winning 10 frames using `bmp8_line()`.
 
-**Demo 2**: load actual vertex content from Blender/Babylon based on [this](https://david.blob.core.windows.net/softengine3d/part3/index.html):
+#### **Demo 2**: load actual vertex content
+
+From Blender/Babylon based on [this](https://david.blob.core.windows.net/softengine3d/part3/index.html).
+
+A JS script has been provided that generates the needed C++ code. It's not great, and not very performant.
 
 ![design](https://github.com/wgroeneveld/gba-bitmap-engine/blob/master/img/monkey.gif?raw=true)
 
@@ -41,7 +47,16 @@ Use the `gba-sprite-engine` instead.
 I am aware of countless optimization opportunities but even thinking about that makes me sleepy. 
 This is a high-level C++ engine, meaning redundant stack objects could also cause problems. And I'm okay with that - it's a proof-of-concept!
 
-#### GBA-Specific problems  
+#### **Demo 3**: rasterization
+
+The `RasterizerRenderer` class draws triangles as 'fast' as possible, using horizontal scanlines. 
+There is a fast way to lines into VRAM. I tried implementing Z-buffering, but the buffer was too big and too slow as z-coords also had to be interpolated... 
+
+![design](https://github.com/wgroeneveld/gba-bitmap-engine/blob/master/img/raster.gif?raw=true)
+
+At this point, I do not think it's that interesting to go on to texture mapping other than the fun of it. Even with a lot of haxx and tricks, the colored monkey won't ever spin at 30FPS... 
+
+### GBA-Specific problems  
 
 **Fixed-point math** sums up things nicely. 
 
@@ -78,3 +93,4 @@ More details in `math.h`.
 
 In any case, lots of rounding errors occur. It is luckily not a problem due to GBA's limited screen dimensions. 
 
+**Limited iWRAM** size is another problem. Use `const` arrays as much as possible!

demos/demo2-blender-import/src/monkey.cpp

@@ -5,8 +5,9 @@
 #include <libgba-sprite-engine/background/text_stream.h>
 #include "monkey.h"
 
-const unsigned short pal[4] __attribute__((aligned(4))) = {
-        0x0000, 0xFFFF, 0x3AE2
+// BLACK, [white->black] from 0xFFFF / 252
+const unsigned short pal[253] __attribute__((aligned(4))) = {
+    0x0000, 65535,32767,21845,16383,13107,10922,9362,8191,7281,6553,5957,5461,5041,4681,4369,4095,3855,3640,3449,3276,3120,2978,2849,2730,2621,2520,2427,2340,2259,2184,2114,2047,1985,1927,1872,1820,1771,1724,1680,1638,1598,1560,1524,1489,1456,1424,1394,1365,1337,1310,1285,1260,1236,1213,1191,1170,1149,1129,1110,1092,1074,1057,1040,1023,1008,992,978,963,949,936,923,910,897,885,873,862,851,840,829,819,809,799,789,780,771,762,753,744,736,728,720,712,704,697,689,682,675,668,661,655,648,642,636,630,624,618,612,606,601,595,590,585,579,574,569,564,560,555,550,546,541,537,532,528,524,520,516,511,508,504,500,496,492,489,485,481,478,474,471,468,464,461,458,455,451,448,445,442,439,436,434,431,428,425,422,420,417,414,412,409,407,404,402,399,397,394,392,390,387,385,383,381,378,376,374,372,370,368,366,364,362,360,358,356,354,352,350,348,346,344,343,341,339,337,336,334,332,330,329,327,326,324,322,321,319,318,316,315,313,312,310,309,307,306,304,303,302,300,299,297,296,295,293,292,291,289,288,287,286,284,283,282,281,280,278,277,276,275,274,273,271,270,269,268,267,266,265,264,263,262,261,260
 };
 
 std::vector<Mesh*> MonkeyScene::meshes() {

engine/src/renderer/raserizerrenderer.cpp

@@ -66,6 +66,7 @@ void RasterizerRenderer::plotTriangle(const VectorFx& pt1, const VectorFx& pt2,
 
 void RasterizerRenderer::render(const MatrixFx &transformationMatrix, const Mesh *mesh) {
     bool colorSwitch = false;
+    int i = 0;
     for (auto &face : mesh->faces()) {
         auto &vertexA = mesh->vertices()[face.a];
         auto &vertexB = mesh->vertices()[face.b];
@@ -75,8 +76,9 @@ void RasterizerRenderer::render(const MatrixFx &transformationMatrix, const Mesh
         auto pixelB = engine->project(*vertexB.get(), transformationMatrix);
         auto pixelC = engine->project(*vertexC.get(), transformationMatrix);
 
-        plotTriangle(pixelA, pixelB, pixelC, colorSwitch ? 2 : 1);
+        COLOR cI = ONE + fxmul(fxdiv(int2fx(i), int2fx(mesh->faces().size())), int2fx(250));
+        plotTriangle(pixelA, pixelB, pixelC, fx2int(cI));
         colorSwitch = !colorSwitch;
+        i++;
     }
-
 }