@@ 43,34 43,33 @@ void DrawTriangle(int *polygon, Vertex *vertices, Color color, Viewport *viewpor
 {
 	assert(NumPolygonVertices(polygon) == 3);
 	Rect bounding_box = PolygonBounds(polygon, vertices);
-	EdgeTracker a = TrackEdge(PolygonVertex(polygon, vertices, 0), PolygonVertex(polygon, vertices, 1), V(bounding_box.left, bounding_box.bottom, 0));
-	EdgeTracker b = TrackEdge(PolygonVertex(polygon, vertices, 1), PolygonVertex(polygon, vertices, 2), V(bounding_box.left, bounding_box.bottom, 0));
-	EdgeTracker c = TrackEdge(PolygonVertex(polygon, vertices, 2), PolygonVertex(polygon, vertices, 0), V(bounding_box.left, bounding_box.bottom, 0));
+	Vertex *a = PolygonVertex(polygon, vertices, 0);
+	Vertex *b = PolygonVertex(polygon, vertices, 1);
+	Vertex *c = PolygonVertex(polygon, vertices, 2);
 
-	for (int y = bounding_box.bottom; y < bounding_box.top; y += 2) {
+	EdgeTracker ab = TrackEdge(a, b, V(bounding_box.left, bounding_box.bottom, 0));
+	EdgeTracker bc = TrackEdge(b, c, V(bounding_box.left, bounding_box.bottom, 0));
+	EdgeTracker ca = TrackEdge(c, a, V(bounding_box.left, bounding_box.bottom, 0));
+	float area = TriArea(a, b, c);
+
+	for (int y = bounding_box.bottom; y < bounding_box.top; y++) {
 		for (int x = bounding_box.left; x <= bounding_box.right; x++) {
-			if (a.value < 0 && b.value < 0 && c.value < 0) {
-				// TryWritePixel(x, y, z, color, viewport);
-				WritePixel(x, y, color, viewport);
-			}
-			a.value += a.dy;
-			b.value += b.dy;
-			c.value += c.dy;
-		}
-		a.value -= a.dx;
-		b.value -= b.dx;
-		c.value -= c.dx;
-		for (int x = bounding_box.right; x >= bounding_box.left; x--) {
-			if (a.value < 0 && b.value < 0 && c.value < 0) {
-				WritePixel(x, y + 1, color, viewport);
+			if (ab.value < 0 && bc.value < 0 && ca.value < 0) {
+				float z = bc.value/area*a->z + b->z*ca.value/area + c->z*ab.value/area;
+				if (UpdateDepthBuffer(x, y, -z, viewport)) {
+					WritePixel(x, y, color, viewport);
+				}
 			}
-			a.value -= a.dy;
-			b.value -= b.dy;
-			c.value -= c.dy;
+			ab.value += ab.dy;
+			bc.value += bc.dy;
+			ca.value += ca.dy;
 		}
-		a.value -= a.dx;
-		b.value -= b.dx;
-		c.value -= c.dx;
+		ab.row_value -= ab.dx;
+		ab.value = ab.row_value;
+		bc.row_value -= bc.dx;
+		bc.value = bc.row_value;
+		ca.row_value -= ca.dx;
+		ca.value = ca.row_value;
 	}
 }
 


@@ 219,13 218,13 @@ void DrawPoint(Vertex p, Color color, Viewport *viewport)
 
 Rect PolygonBounds(int *polygon, Vertex *vertices)
 {
-	Rect r = { floor(vertices[0].x), floor(vertices[0].y), floor(vertices[0].x), floor(vertices[0].y) };
+	Rect r = { floor(vertices[0].x), floor(vertices[0].y), ceil(vertices[0].x), ceil(vertices[0].y) };
 	for (int i = 0; i < *polygon; i++) {
 		Vertex v = vertices[polygon[i+1]];
 		if (v.x < r.left)		r.left = floor(v.x);
-		if (v.x > r.right)		r.right = floor(v.x);
+		if (v.x > r.right)		r.right = ceil(v.x);
 		if (v.y < r.bottom)		r.bottom = floor(v.y);
-		if (v.y > r.top)		r.top = floor(v.y);
+		if (v.y > r.top)		r.top = ceil(v.y);
 	}
 	return r;
 }


@@ 244,5 243,12 @@ EdgeTracker TrackEdge(Vertex *a, Vertex *b, Vertex start)
 	et.dx = b->x - a->x;
 	et.dy = b->y - a->y;
 	et.value = (start.x - a->x)*et.dy - (start.y - a->y)*et.dx;
+	et.row_value = et.value;
 	return et;
 }
+
+float TriArea(Vertex *a, Vertex *b, Vertex *c)
+/* Returns twice the signed area of the triangle */
+{
+	return (b->x - a->x)*(c->y - a->y) - (c->x - a->x)*(b->y - a->y);
+}

@@ 39,6 39,7 @@ typedef struct Rect {
 typedef struct EdgeTracker {
 	float dx;
 	float dy;
+	float row_value;
 	float value;
 } EdgeTracker;
 


@@ 60,3 61,4 @@ void DrawPoint(Vertex p, Color color, Viewport *viewport);
 Rect PolygonBounds(int *polygon, Vertex *vertices);
 void PrintRect(Rect r);
 EdgeTracker TrackEdge(Vertex *a, Vertex *b, Vertex start);
+float TriArea(Vertex *a, Vertex *b, Vertex *c);

@@ 8,7 8,7 @@ void TestRandomTriangles(void)
 {
 	Scene *scene = NewScene();
 
-	for (int i = 0; i < 10000; ++i) {
+	for (int i = 0; i < 9999; ++i) {
 		Model *model = NewModel(scene->model_pool);
 		Renderable *r = NewRenderable(scene->renderable_pool, model, BLACK);
 		Vertex *a = NewVertex(r->mesh->vertices);


@@ 37,9 37,12 @@ void TestRandomTriangles(void)
 
 	float clocksPerMs = CLOCKS_PER_SEC/1000;
 	float startTime = (float)clock()/(clocksPerMs);
-	RenderScene(scene, renderer);
+	int numRenders = 100;
+	for (int i = 0; i < numRenders; i++) {
+		RenderScene(scene, renderer);
+	}
 	float endTime = (float)clock()/(clocksPerMs);
-	float renderTime = (endTime - startTime);
+	float renderTime = (endTime - startTime) / numRenders;
 
 	float targetTime = (1/30.f)*1000; // one frame, ~33 ms
 	printf("Render time: %.2fms (target max: %.2fms)\n", renderTime, targetTime);