Add inverse z-buffering

Makefile

@@ -31,7 +31,8 @@ CC=clang++
 WARNINGS_ON=-Weverything
 WARNINGS_OFF=-Wno-missing-braces -Wno-gnu-anonymous-struct -Wno-old-style-cast\
 			 -Wno-zero-as-null-pointer-constant -Wno-nested-anon-types\
-			 -Wno-padded -Wno-exit-time-destructors -Wno-global-constructors
+			 -Wno-padded -Wno-exit-time-destructors -Wno-global-constructors\
+			 -Wno-c++98-compat
 
 CFLAGS=$(D) $(O) -std=c++11 $(WARNINGS_ON) $(WARNINGS_OFF) -I$(INCLUDE_DIR)
 LIBS=-lSDL2

include/engine.h

@@ -26,7 +26,8 @@ enum Engine_Input
 // STRUCTURES
 struct Engine_Buffer
 {
-    uint32_t *pixels;
+    uint32_t *buffer;
+    float *zbuffer;
     int width;
     int height;
 };

include/geometry.h

@@ -77,10 +77,11 @@ struct Mesh
 
 // PUBLIC FUNCTIONS
 void FillTriangle(
-        uint32_t *buffer, int width, uint32_t color,
+        uint32_t *buffer, int width,
-        float x0, float y0,
+        float *zbuffer, uint32_t color,
-        float x1, float y1,
+        float x0, float y0, float z0,
-        float x2, float y2);
+        float x1, float y1, float z1,
+        float x2, float y2, float z2);
 
 
 #define GEOMETRY_H

include/matrix.h

@@ -74,6 +74,13 @@ inline Point operator*(Point v, Matrix m)
     return result;
 }
 
+inline Point &operator*=(Point &v, Matrix m)
+{
+    v = v * m;
+
+    return v;
+}
+
 
 #define MATRIX_H
 #endif

include/point.h

@@ -36,6 +36,14 @@ inline Point operator/(Point v, float f)
     return result;
 }
 
+// v /= f
+inline Point &operator/=(Point &v, float f)
+{
+    v = v / f;
+
+    return v;
+}
+
 // v1 - v2
 inline Vector operator-(Point v1, Point v2)
 {

src/engine.cpp

@@ -8,7 +8,7 @@
 #include "transform.h"
 #include "util.h"
 #include "vec.h"
-#include <cstdio>
+#include <cstring>
 
 
 // GLOBALS
@@ -50,6 +50,8 @@ void Engine_Render(Engine_Buffer &buffer, uint32_t input)
 {
     CheckInputs(input);
 
+    unsigned long bufferSize = (unsigned long)(buffer.width * buffer.height);
+    memset(buffer.zbuffer, 0, bufferSize * sizeof(float));
 
     // Local space to world space
     Matrix tTranslate = Transform_Translate(
@@ -62,8 +64,7 @@ void Engine_Render(Engine_Buffer &buffer, uint32_t input)
 
     for (size_t v = 0; v < mesh.verts.size(); ++v)
     {
-        mesh.vertsTransformed[v] =
+        mesh.vertsTransformed[v] = mesh.verts[v] * tScale * tRotate * tTranslate;
-            mesh.verts[v] * tScale * tRotate * tTranslate;
     }
 
 
@@ -99,25 +100,17 @@ void Engine_Render(Engine_Buffer &buffer, uint32_t input)
     // World space to camera (view) space
     Matrix tView = Transform_View(camera.position, camera.rotation);
 
-
     // Camera space to perspective
     Matrix tPersp = Transform_Perspective(
             camera.xZoom, camera.yZoom, camera.nearClip, camera.farClip);
 
-    for (size_t v = 0; v < mesh.verts.size(); ++v)
-    {
-        mesh.vertsTransformed[v] = mesh.vertsTransformed[v] * tView * tPersp;
-
-        mesh.vertsTransformed[v] =
-            mesh.vertsTransformed[v] / mesh.vertsTransformed[v].w;
-    }
-
     // Perspective to screen
     Matrix tScreen = Transform_Screen(camera.xScale, camera.yScale);
 
     for (size_t v = 0; v < mesh.verts.size(); ++v)
     {
-        mesh.vertsTransformed[v] = mesh.vertsTransformed[v] * tScreen;
+        mesh.vertsTransformed[v] *= tView * tPersp * tScreen;
+        mesh.vertsTransformed[v] /= mesh.vertsTransformed[v].w;
     }
 
 
@@ -129,10 +122,11 @@ void Engine_Render(Engine_Buffer &buffer, uint32_t input)
         unsigned int v2 = mesh.culledFaces[f].vertIndex[2];
 
         FillTriangle(
-                buffer.pixels, buffer.width, mesh.faces[f].color.u32,
+                buffer.buffer, buffer.width,
-                mesh.vertsTransformed[v0].x, mesh.vertsTransformed[v0].y,
+                buffer.zbuffer, mesh.faces[f].color.u32,
-                mesh.vertsTransformed[v1].x, mesh.vertsTransformed[v1].y,
+                mesh.vertsTransformed[v0].x, mesh.vertsTransformed[v0].y, mesh.vertsTransformed[v0].z,
-                mesh.vertsTransformed[v2].x, mesh.vertsTransformed[v2].y);
+                mesh.vertsTransformed[v1].x, mesh.vertsTransformed[v1].y, mesh.vertsTransformed[v1].z,
+                mesh.vertsTransformed[v2].x, mesh.vertsTransformed[v2].y, mesh.vertsTransformed[v2].z);
     }
 }
 

src/geometry.cpp

@@ -12,24 +12,27 @@
 
 // PRIVATE PROTOTYPES
 static void FillTriangleFlatBottom(
-        uint32_t *buffer, int width, uint32_t color,
+        uint32_t *buffer, int width,
-        float x0, float y0,
+        float *zbuffer, uint32_t color,
-        float x1, float y1,
+        float x0, float y0, float z0,
-        float x2, float y2);
+        float x1, float y1, float z1,
+        float x2, float y2, float z2);
 
 static void FillTriangleFlatTop(
-        uint32_t *buffer, int width, uint32_t color,
+        uint32_t *buffer, int width,
-        float x0, float y0,
+        float *zbuffer, uint32_t color,
-        float x1, float y1,
+        float x0, float y0, float z0,
-        float x2, float y2);
+        float x1, float y1, float z1,
+        float x2, float y2, float z2);
 
 
 // PUBLIC FUNCTIONS
 void FillTriangle(
-        uint32_t *buffer, int width, uint32_t color,
+        uint32_t *buffer, int width,
-        float x0, float y0,
+        float *zbuffer, uint32_t color,
-        float x1, float y1,
+        float x0, float y0, float z0,
-        float x2, float y2)
+        float x1, float y1, float z1,
+        float x2, float y2, float z2)
 {
     // Horizontal or vertical
     if ((FLOAT_EQUAL(x0,x1) && FLOAT_EQUAL(x1, x2))
@@ -44,31 +47,34 @@ void FillTriangle(
     {
         SWAP(x0, x1, temp);
         SWAP(y0, y1, temp);
+        SWAP(z0, z1, temp);
     }
 
     if (y0 > y2)
     {
         SWAP(x0, x2, temp);
         SWAP(y0, y2, temp);
+        SWAP(z0, z2, temp);
     }
 
     if (y1 > y2)
     {
         SWAP(x1, x2, temp);
         SWAP(y1, y2, temp);
+        SWAP(z1, z2, temp);
     }
 
 
     // Flat top triangle
     if (FLOAT_EQUAL(y0, y1))
     {
-        FillTriangleFlatTop(buffer, width, color, x0, y0, x1, y1, x2, y2);
+        FillTriangleFlatTop(buffer, width, zbuffer, color, x0, y0, z0, x1, y1, z1, x2, y2, z2);
     }
 
     // Flat bottom triangle
     else if (FLOAT_EQUAL(y1, y2))
     {
-        FillTriangleFlatBottom(buffer, width, color, x0, y0, x1, y1, x2, y2);
+        FillTriangleFlatBottom(buffer, width, zbuffer, color, x0, y0, z0, x1, y1, z1, x2, y2, z2);
     }
 
     // Other - decompose into two triangles
@@ -78,27 +84,30 @@ void FillTriangle(
         // New y is the same as y1
         float x3 = x0 + (((y1 - y0) / (y2 - y0)) * (x2 - x0));
         float y3 = y1;
+        float z3 = z1;
 
-        FillTriangleFlatBottom(buffer, width, color, x0, y0, x1, y1, x3, y3);
+        FillTriangleFlatBottom(buffer, width, zbuffer, color, x0, y0, z0, x1, y1, z1, x3, y3, z3);
-        FillTriangleFlatTop(buffer, width, color, x1, y1, x3, y3, x2, y2);
+        FillTriangleFlatTop(buffer, width, zbuffer, color, x1, y1, z1, x3, y3, z3, x2, y2, z2);
     }
 }
 
 
 // PRIVATE FUNCTIONS
 static void FillTriangleFlatBottom(
-        uint32_t *buffer, int width, uint32_t color,
+        uint32_t *buffer, int width,
-        float x0, float y0,
+        float *zbuffer, uint32_t color,
-        float x1, float y1,
+        float x0, float y0, float z0,
-        float x2, float y2)
+        float x1, float y1, float z1,
+        float x2, float y2, float z2)
 {
     if (x2 < x1)
     {
         float temp;
-        SWAP(x1, x2, temp);
+        SWAP(x2, x1, temp);
+        SWAP(y2, y1, temp);
+        SWAP(z2, z1, temp);
     }
 
-
     // Top-left fill convention
     float dxdy_left = (x1 - x0) / (y1 - y0);
     float dxdy_right = (x2 - x0) / (y2 - y0);
@@ -108,35 +117,62 @@ static void FillTriangleFlatBottom(
     float xEnd = x0 + dxdy_right * (yStart - y0);
 
 
+    // Inverse z-buffering
+    float z0Inv = 1.0f / z0;
+    float z1Inv = 1.0f / z1;
+    float z2Inv = 1.0f / z2;
+    float dzdy_left = (z1Inv - z0Inv) / (y1 - y0);
+    float dzdy_right = (z2Inv - z0Inv) / (y2 - y0);
+    float zStart = z0Inv;
+    float zEnd = z0Inv;
+
+
     // Fill
     for (int y = yStart; y <= yEnd; ++y)
     {
+        float dzdx = (zEnd - zStart) / (xEnd - xStart);
+        float z = zStart;
+
         int xStartInt = (int)xStart;
         int xEndInt = (int)xEnd;
 
         for (int x = xStartInt; x <= xEndInt; ++x)
+        {
+            int pixel = (y * width) + x;
+
+            if (z > zbuffer[pixel])
             {
                 DrawPixel(buffer, width, color, x, y);
+
+                zbuffer[pixel] = z;
+            }
+
+            z += dzdx;
         }
 
         xStart += dxdy_left;
         xEnd += dxdy_right;
+
+        zStart += dzdy_left;
+        zEnd += dzdy_right;
     }
 }
 
 static void FillTriangleFlatTop(
-        uint32_t *buffer, int width, uint32_t color,
+        uint32_t *buffer, int width,
-        float x0, float y0,
+        float *zbuffer, uint32_t color,
-        float x1, float y1,
+        float x0, float y0, float z0,
-        float x2, float y2)
+        float x1, float y1, float z1,
+        float x2, float y2, float z2)
 {
     if (x1 < x0)
     {
         float temp;
         SWAP(x1, x0, temp);
+        SWAP(y1, y0, temp);
+        SWAP(z1, z0, temp);
     }
 
-
     // Top-left fill convention
     float dxdy_left = (x2 - x0) / (y2 - y0);
     float dxdy_right = (x2 - x1) / (y2 - y1);
@@ -146,19 +182,43 @@ static void FillTriangleFlatTop(
     float xEnd = x1 + dxdy_right * (yStart - y0);
 
 
+    // Inverse z-buffering
+    float z0Inv = 1.0f / z0;
+    float z1Inv = 1.0f / z1;
+    float z2Inv = 1.0f / z2;
+    float dzdy_left = (z2Inv - z0Inv) / (y2 - y0);
+    float dzdy_right = (z2Inv - z1Inv) / (y2 - y1);
+    float zStart = z0Inv;
+    float zEnd = z1Inv;
+
     // Fill
     for (int y = yStart; y <= yEnd; ++y)
     {
+        float dzdx = (zEnd - zStart) / (xEnd - xStart);
+        float z = zStart;
+
         int xStartInt = (int)xStart;
         int xEndInt = (int)xEnd;
 
         for (int x = xStartInt; x <= xEndInt; ++x)
+        {
+            int pixel = (y * width) + x;
+
+            if (z > zbuffer[pixel])
             {
                 DrawPixel(buffer, width, color, x, y);
+
+                zbuffer[pixel] = z;
+            }
+
+            z += dzdx;
         }
 
         xStart += dxdy_left;
         xEnd += dxdy_right;
+
+        zStart += dzdy_left;
+        zEnd += dzdy_right;
     }
 }
 

src/main.cpp

@@ -29,7 +29,8 @@ int main(int argc, char *argv[])
     if (result == PLATFORM_OK)
     {
         Engine_Buffer buffer = {};
-        buffer.pixels = (uint32_t*)platform.surface->pixels;
+        buffer.buffer = (uint32_t*)platform.surface->pixels;
+        buffer.zbuffer = (float*)calloc((size_t)(platform.surface->w * platform.surface->h), sizeof(float));
         buffer.width = platform.surface->w;
         buffer.height = platform.surface->h;