@@ 10,7 10,6 @@ support the to-be-released Playdate handheld console.
 ## TODO
 
 - Use ints for rasterization
-- Implement [Pineda triangle raster algorithm][pineda]
 - Use [guard-band clipping][clipping]
 - Add sub-pixel precision
 - Gouraud shading

@@ 43,7 43,7 @@ int main(void)
 
 			// one-shot
 			// UpdateScene(scene, 1);
-			// ClearScreen(gameRenderer);
+			// ClearScreen(gameRenderer->viewport);
 			// RenderScene(scene, gameRenderer);
 
 			/* variables for perf statistics */


@@ 103,10 103,14 @@ Scene *MoonWorld(void)
 {
 	Scene *scene = NewScene();
 	SceneObject *obj = CreateSceneObject(scene, "assets/cube.obj", BLACK);
+	obj->renderable->color = LT_GRAY;
+	SceneObject *obj2 = CloneSceneObject(scene, obj);
+	obj2->renderable->color = DK_GRAY;
 	PlaceModel(obj->model, V(0, 0, -10));
 	Spin(obj->physics, V(1, 1, 0), 0.1);
 	Spin(obj->physics, V(0, 1, 1), 0.05);
 	Spin(obj->physics, V(0, 1, 0), 0.1);
+	PlaceModel(obj2->model, V(3, 0, -15));
 
 	// InitParticleSystem(scene);
 	// for (int i = 0; i < 1000; i++) {

@@ 78,27 78,6 @@ void PrintPolygon(int *polygon, Vertex *vertices)
 		PrintVec(*PolygonVertex(polygon, vertices, i));
 	}
 	printf("\n");
-	fflush(stdout);
-}
-
-Rect PolygonBounds(int *polygon, Vertex *vertices)
-{
-	Rect r = { vertices[0].x, vertices[0].y, vertices[0].x, vertices[0].y };
-	for (int i = 0; i < NumPolygonVertices(polygon); i++) {
-		Vertex *v = PolygonVertex(polygon, vertices, i);
-		if (v->x < r.left)		r.left = v->x;
-		if (v->x > r.right)		r.right = v->x;
-		if (v->y < r.top)		r.top = v->y;
-		if (v->y > r.bottom)	r.bottom = v->y;
-	}
-	return r;
-}
-
-void PrintRect(Rect r)
-{
-	printf("%6.2f, %6.2f┌───┐%6.2f, %6.2f\n",  r.top, r.left, r.top, r.right);
-	printf("              │   │\n");
-	printf("%6.2f, %6.2f└───┘%6.2f, %6.2f\n", r.bottom, r.left, r.bottom, r.right);
 }
 
 void Triangularize(int *polygon, Mesh *mesh)

@@ 3,13 3,6 @@
 #include "vector.h"
 #include "pool.h"
 
-typedef struct Rect {
-	float top;
-	float left;
-	float right;
-	float bottom;
-} Rect;
-
 typedef struct Mesh {
   Vertex *vertices;
   int *faces;


@@ 33,6 26,4 @@ Vertex *NewVertex(Vertex *pool);
 
 int *NewPolygon(int *pool);
 void PrintPolygon(int *polygon, Vertex *vertices);
-Rect PolygonBounds(int *polygon, Vertex *vertices);
-void PrintRect(Rect r);
 void Triangularize(int *polygon, Mesh *mesh);

@@ 59,8 59,8 @@ void Render(Renderable renderable, Renderer *renderer, Transform camera_transfor
 		 i < PoolTotal(renderMesh.faces);
 		 i += NumPolygonVertices(polygon)+1, NextPolygon(polygon)) {
 		if (NumPolygonVertices(polygon) > 0) {
-			RasterizePolygon(polygon, renderMesh.vertices, renderer->viewport);
-			WireframePolygon(polygon, renderMesh.vertices, renderer->viewport);
+			DrawPolygon(polygon, renderMesh.vertices, renderable.color, renderer->viewport);
+			// WireframePolygon(polygon, renderMesh.vertices, renderer->viewport);
 		}
 	}
 }

@@ 50,6 50,16 @@ SceneObject *NewSceneObject(SceneObject *pool, Model *model, Renderable *rendera
 	return obj;
 }
 
+SceneObject *CloneSceneObject(Scene *scene, SceneObject *obj)
+{
+	Model *model = NewModel(scene->model_pool);
+	Renderable *renderable = NewRenderable(scene->renderable_pool, model, obj->renderable->color);
+	renderable->mesh = obj->renderable->mesh;
+	Physics *physics = NewPhysics(scene->physics_pool, model);
+	SceneObject *clone = NewSceneObject(scene->objects, model, renderable, physics);
+	return clone;
+}
+
 void InitParticleSystem(Scene *scene)
 /* Activates a Scene's particle pool. Presence of this pool will also enable
 particle processing.

@@ 26,6 26,7 @@ Scene *NewScene(void);
 SceneObject *CreateSceneObject(Scene *scene, const char *meshFile, Color color);
 SceneObject *NewSceneObjectPool(void);
 SceneObject *NewSceneObject(SceneObject *pool, Model *model, Renderable *renderable, Physics *physics);
+SceneObject *CloneSceneObject(Scene *scene, SceneObject *obj);
 void InitParticleSystem(Scene *scene);
 void UpdateScene(Scene *scene, int dt);
 void RenderScene(Scene *scene, Renderer *renderer);

@@ 2,6 2,8 @@
 #include "mesh.h"
 #include <math.h>
 #include <stdlib.h>
+#include <assert.h>
+#include <stdio.h>
 
 Viewport *NewViewport(Pixel *pixels, Color background_color, int width, int height)
 {


@@ 37,21 39,49 @@ void ClearScreen(Viewport *viewport)
 	}
 }
 
-void RasterizePolygon(int *polygon, Vertex *vertices, Viewport *viewport)
+void DrawPolygon(int *polygon, Vertex *vertices, Color color, Viewport *viewport)
 {
+	assert(NumPolygonVertices(polygon) == 3);
 	Rect bounding_box = PolygonBounds(polygon, vertices);
-	DrawBoundingBox(bounding_box, viewport);
+	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));
+
+	for (int y = bounding_box.bottom; y < bounding_box.top; y += 2) {
+		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);
+			}
+			a.value -= a.dy;
+			b.value -= b.dy;
+			c.value -= c.dy;
+		}
+		a.value -= a.dx;
+		b.value -= b.dx;
+		c.value -= c.dx;
+	}
 }
 
 void DrawBoundingBox(Rect bounding_box, Viewport *viewport)
 {
-	RasterLine(V(bounding_box.left, bounding_box.top, 0), V(bounding_box.right, bounding_box.top, 0), GRAY, viewport);
-	RasterLine(V(bounding_box.right, bounding_box.top, 0), V(bounding_box.right, bounding_box.bottom, 0), GRAY, viewport);
-	RasterLine(V(bounding_box.left, bounding_box.bottom, 0), V(bounding_box.right, bounding_box.bottom, 0), GRAY, viewport);
-	RasterLine(V(bounding_box.left, bounding_box.top, 0), V(bounding_box.left, bounding_box.bottom, 0), GRAY, viewport);
+	DrawLine(V(bounding_box.left, bounding_box.top, 0), V(bounding_box.right, bounding_box.top, 0), GRAY, viewport);
+	DrawLine(V(bounding_box.right, bounding_box.top, 0), V(bounding_box.right, bounding_box.bottom, 0), GRAY, viewport);
+	DrawLine(V(bounding_box.left, bounding_box.bottom, 0), V(bounding_box.right, bounding_box.bottom, 0), GRAY, viewport);
+	DrawLine(V(bounding_box.left, bounding_box.top, 0), V(bounding_box.left, bounding_box.bottom, 0), GRAY, viewport);
 }
 
-// TODO: find a more efficient way to wireframe a mesh without duplicating edges
 void WireframePolygon(int *polygon, Vertex *vertices, Viewport *viewport)
 /* Rasterizes lines between each edge of a polygon */
 {


@@ 59,31 89,31 @@ void WireframePolygon(int *polygon, Vertex *vertices, Viewport *viewport)
 	previous = LastPolygonVertex(polygon, vertices);
 	for (int i = 0; i < NumPolygonVertices(polygon); i++) {
 		current = PolygonVertex(polygon, vertices, i);
-		RasterLine(*previous, *current, BLACK, viewport);
+		DrawLine(*previous, *current, BLACK, viewport);
 		previous = current;
 	}
 }
 
-void RasterLine(Vertex a, Vertex b, Color color, Viewport *viewport)
+void DrawLine(Vertex a, Vertex b, Color color, Viewport *viewport)
 {
 	double dx = b.x - a.x;
 	double dy = b.y - a.y;
 	if (fabs(dy) < fabs(dx)) {
 		if (a.x > b.x) {
-			RasterLineShallow(b, a, color, viewport);
+			DrawLineShallow(b, a, color, viewport);
 		} else {
-			RasterLineShallow(a, b, color, viewport);
+			DrawLineShallow(a, b, color, viewport);
 		}
 	} else {
 		if (a.y > b.y) {
-			RasterLineSteep(b, a, color, viewport);
+			DrawLineSteep(b, a, color, viewport);
 		} else {
-			RasterLineSteep(a, b, color, viewport);
+			DrawLineSteep(a, b, color, viewport);
 		}
 	}
 }
 
-void RasterLineShallow(Vertex a, Vertex b, Color color, Viewport *viewport)
+void DrawLineShallow(Vertex a, Vertex b, Color color, Viewport *viewport)
 {
 	double dx = b.x - a.x;
 	double dy = b.y - a.y;


@@ 110,7 140,7 @@ void RasterLineShallow(Vertex a, Vertex b, Color color, Viewport *viewport)
 	}
 }
 
-void RasterLineSteep(Vertex a, Vertex b, Color color, Viewport *viewport)
+void DrawLineSteep(Vertex a, Vertex b, Color color, Viewport *viewport)
 {
 	double dx = b.x - a.x;
 	double dy = b.y - a.y;


@@ 146,6 176,13 @@ void WritePixel(int x, int y, Color color, Viewport *viewport)
 	}
 }
 
+void TryWritePixel(int x, int y, double z, Color color, Viewport *viewport)
+{
+	if (UpdateDepthBuffer(x, y, z, viewport)) {
+		WritePixel(x, y, color, viewport);
+	}
+}
+
 Color GetPixel(int x, int y, Viewport *viewport)
 /* Reads a pixel from a viewport's frame buffer */
 {


@@ 179,3 216,33 @@ void DrawPoint(Vertex p, Color color, Viewport *viewport)
 		WritePixel(p.x, p.y, color, 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) };
+	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.y < r.bottom)		r.bottom = floor(v.y);
+		if (v.y > r.top)		r.top = floor(v.y);
+	}
+	return r;
+}
+
+void PrintRect(Rect r)
+{
+	printf("%3d, %3d┌───┐%3d, %3d\n",  r.left, r.top, r.right, r.top);
+	printf("        │   │\n");
+	printf("%3d, %3d└───┘%3d, %3d\n", r.left, r.bottom, r.right, r.bottom);
+	fflush(stdout);
+}
+
+EdgeTracker TrackEdge(Vertex *a, Vertex *b, Vertex start)
+{
+	EdgeTracker et;
+	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;
+	return et;
+}

@@ 29,17 29,34 @@ typedef struct Viewport {
 	int height;
 } Viewport;
 
+typedef struct Rect {
+	int left;
+	int bottom;
+	int right;
+	int top;
+} Rect;
+
+typedef struct EdgeTracker {
+	float dx;
+	float dy;
+	float value;
+} EdgeTracker;
+
 Viewport *NewViewport(Pixel *pixels, Color background_color, int width, int height);
 DepthVal *NewDepthBuffer(int width, int height);
 void ClearScreen(Viewport *viewport);
-void RasterizePolygon(int *polygon, Vertex *vertices, Viewport *viewport);
+void DrawPolygon(int *polygon, Vertex *vertices, Color color, Viewport *viewport);
 void DrawBoundingBox(Rect boundingBox, Viewport *viewport);
 void WireframePolygon(int *polygon, Vertex *vertices, Viewport *viewport);
+void TryWritePixel(int x, int y, double z, Color color, Viewport *viewport);
 void WritePixel(int x, int y, Color color, Viewport *viewport);
 Color GetPixel(int x, int y, Viewport *viewport);
 void WriteDepth(int x, int y, DepthVal value, Viewport *viewport);
-void RasterLineSteep(Vertex a, Vertex b, Color color, Viewport *viewport);
-void RasterLineShallow(Vertex a, Vertex b, Color color, Viewport *viewport);
-void RasterLine(Vertex a, Vertex b, Color color, Viewport *viewport);
+void DrawLineSteep(Vertex a, Vertex b, Color color, Viewport *viewport);
+void DrawLineShallow(Vertex a, Vertex b, Color color, Viewport *viewport);
+void DrawLine(Vertex a, Vertex b, Color color, Viewport *viewport);
 bool UpdateDepthBuffer(int x, int y, double z, Viewport *viewport);
-void DrawPoint(Vertex p, Color color, Viewport *viewport);>
\ No newline at end of file
+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);