@@ 12,7 12,7 @@ TESTS := $(shell find $(TEST_DIRS) -name *.test.c)
 TEST_OBJS := $(TESTS:%=$(BUILD_DIR)/%.o) $(SRCS:%=$(BUILD_DIR)/%.test.o)
 
 CC = gcc
-CFLAGS = -I/usr/local/include/SDL2 -O2 -g -Wall -Wextra -Wno-unused-function
+CFLAGS = -I/usr/local/include/SDL2 -O0 -g -Wall -Wextra -Wno-unused-function
 LDFLAGS = -L/usr/local/lib -lSDL2 -lm
 TESTFLAGS = -DTEST
 

@@ 42,10 42,11 @@ int main(void)
 			Renderer *gameRenderer = NewRenderer(pixels, SCREEN_WIDTH, SCREEN_HEIGHT, scene->camera);
 
 			// one-shot
-			UpdateScene(scene, 1);
-			ClearScreen(gameRenderer);
-			RenderScene(scene, gameRenderer);
+			// UpdateScene(scene, 1);
+			// ClearScreen(gameRenderer);
+			// RenderScene(scene, gameRenderer);
 
+			/* variables for perf statistics */
 			long frames = 0;
 			long start = SDL_GetTicks();
 			long dt = 0;


@@ 55,10 56,13 @@ int main(void)
 
 				dt = SDL_GetTicks() - lastTime;
 				lastTime = SDL_GetTicks();
-				// UpdateScene(scene, dt);
-				// ClearScreen(gameRenderer);
-				// RenderScene(scene, gameRenderer);
 
+				/* main game loop */
+				UpdateScene(scene, dt);
+				ClearScreen(gameRenderer);
+				RenderScene(scene, gameRenderer);
+
+				/* copy our framebuffer to SDL for display */
 				SDL_UpdateTexture(texture, NULL, pixels, SCREEN_WIDTH*sizeof(uint32_t));
 				SDL_RenderCopy(renderer, texture, NULL, NULL);
 				SDL_RenderPresent(renderer);


@@ 68,12 72,14 @@ int main(void)
 				//  done = SDL_TRUE;
 				// }
 
+				/* listen for a quit event */
 				while (SDL_PollEvent(&event)) {
 					if (event.type == SDL_QUIT) {
 						done = SDL_TRUE;
 					}
 				}
 			}
+			/* display perf stats */
 			long time = (SDL_GetTicks() - start)/1000;
 			double fps = (double)frames/(double)time;
 			printf("%f fps\n", fps);


@@ 88,22 94,11 @@ int main(void)
 #endif
 
 Scene *MoonWorld(void)
+/* A wrapper for creating and setting up a moon scene */
 {
 	Scene *scene = NewScene();
-	scene->camera->far = 50;
-	scene->camera->near = 1;
-	// scene->camera->physics->rotation = V(0, 0.1, 0);
-	// PlaceModel(scene->camera->model, V(0, 0, 5));
-	RotateModel(scene->camera->model, 0, -90, 0);
 	SceneObject *obj = CreateSceneObject(scene, "assets/cube.obj", BLACK);
 	PlaceModel(obj->model, V(0, 0, -10));
-	// CommitTransform(RotationY(10), &obj->model->direction);
-	// obj->physics->velocity = V(-0.001, 0, 0);
-	// PlaceModel(obj->model, V(-1, 0, 0));
-	// ScaleObject(obj, 10, 10, 10);
-	// SpinObject(obj, 0, 1, 0);
-
-	// DumpMesh(cube->renderable->mesh);
 
 	InitParticleSystem(scene);
 	for (int i = 0; i < 1000; i++) {


@@ 120,6 115,15 @@ Scene *MoonWorld(void)
 }
 
 Scene *NewScene(void)
+/* Allocates and initializes a Scene.
+A scene tracks all SceneObjects and all of their component parts. It owns global
+memory pools (to which other objects may have a reference). Pools exist for
+SceneObject, Renderable, Physics, Model, and Particle. The Particle pool is
+initially NULL, and must be enabled separately.
+
+Note that Scene does not track vertex or polygon pools. Those are owned
+individually by each Mesh, as well as temporary rendering pools in Renderer.
+*/
 {
 	Scene *scene = malloc(sizeof(Scene));
 	scene->objects = NewPool(SceneObject, MAX_SCENE_OBJECTS);


@@ 134,6 138,7 @@ Scene *NewScene(void)
 }
 
 bool LoadObj(const char *filename, Mesh *mesh)
+/* Loads an OBJ file into an empty Mesh. Returns success or failure. */
 {
 	FILE *fp;
 	bool fileOk = true;


@@ 155,6 160,9 @@ bool LoadObj(const char *filename, Mesh *mesh)
 }
 
 bool ReadObjLine(FILE *fp, Mesh *mesh)
+/* Reads the line type based on the first few characters and delegates parsing
+to subroutines. Right now we only support OBJ_VERTEX and OBJ_FACE.
+*/
 {
 	char itemType[8];
 	if (fscanf(fp, "%8s", itemType) == 1) {


@@ 178,6 186,7 @@ bool ReadObjLine(FILE *fp, Mesh *mesh)
 }
 
 bool ReadObjVertex(FILE *fp, Mesh *mesh)
+/* Reads and appends a vertex to the mesh's vertex pool */
 {
 	float x, y, z, w;
 	bool match;


@@ 191,13 200,13 @@ bool ReadObjVertex(FILE *fp, Mesh *mesh)
 	match = fscanf(fp, "%f", &w);
 	if (!match) w = 1.0;
 
-	/* mesh->vertices should be at the beginning of a pool */
 	Vertex *vertex = NewVertex(mesh->vertices);
 	*vertex = V4D(x, y, z, w);
 	return true;
 }
 
 bool ReadObjFace(FILE *fp, Mesh *mesh)
+/* Reads and appends a face to the mesh's polygon pool */
 {
 	int *polygon = NewPolygon(mesh->faces);
 	int vIndex;


@@ 231,6 240,7 @@ ObjLineType ParseLineType(const char *type)
 }
 
 SceneObject *CreateSceneObject(Scene *scene, const char *meshFile, Color color)
+/* Convenience function to load and create a SceneObject with an OBJ file */
 {
 	Model *model = NewModel(scene->model_pool);
 	Renderable *renderable = NewRenderable(scene->renderable_pool, model, color);


@@ 241,6 251,7 @@ SceneObject *CreateSceneObject(Scene *scene, const char *meshFile, Color color)
 }
 
 Renderable *NewRenderable(Renderable *pool, Model *model, Color color)
+/* Creates and initializes a Renderable in a memory pool */
 {
 	assert(PoolTotal(pool) < MAX_SCENE_OBJECTS);
 	Renderable *renderable = PoolNext(pool);


@@ 251,6 262,7 @@ Renderable *NewRenderable(Renderable *pool, Model *model, Color color)
 }
 
 Physics *NewPhysics(Physics *pool, Model *model)
+/* Creates and initializes a Physics in a memory pool */
 {
 	assert(PoolTotal(pool) < MAX_SCENE_OBJECTS);
 	Physics *physics = PoolNext(pool);


@@ 262,6 274,16 @@ Physics *NewPhysics(Physics *pool, Model *model)
 }
 
 int *NewRawPool(int item_size, int max_items)
+/* Allocates and initializes a memory pool. Used by the `NewPool` macro.
+A memory pool is just a plain array of some item, except that immediately
+preceding it in memory is an int tracking the number of current items. Access
+is done by array subscripts, e.g. `Thing x = my_pool[12];`, but modifying the
+pool should be done through pool macros.
+
+`NewRawPool` allocates the memory for a pool and returns a pointer to the
+counter int. `NewPool` uses this, but returns a pointer to the first element,
+which is usually more useful.
+*/
 {
 	int *raw_pool = malloc(item_size*(max_items) + sizeof(int));
 	raw_pool[0] = 0;


@@ 269,6 291,7 @@ int *NewRawPool(int item_size, int max_items)
 }
 
 SceneObject *NewSceneObject(SceneObject *pool, Model *model, Renderable *renderable, Physics *physics)
+/* Creates and initialized a new SceneObject */
 {
 	assert(PoolTotal(pool) < MAX_SCENE_OBJECTS);
 	SceneObject *obj = PoolNext(pool);


@@ 279,11 302,15 @@ SceneObject *NewSceneObject(SceneObject *pool, Model *model, Renderable *rendera
 }
 
 void InitParticleSystem(Scene *scene)
+/* Activates a Scene's particle pool. Presence of this pool will also enable
+particle processing.
+*/
 {
 	scene->particles = NewPool(Particle, MAX_PARTICLES);
 }
 
 Particle *AddParticle(Particle *pool, Vertex v)
+/* Creates and initializes a Particle */
 {
 	assert(PoolTotal(pool) < MAX_PARTICLES);
 	Particle *p = PoolNext(pool);


@@ 294,6 321,11 @@ Particle *AddParticle(Particle *pool, Vertex v)
 }
 
 Renderer *NewRenderer(Pixel *pixels, int width, int height, Camera *camera)
+/* Creates and initializes a Renderer.
+The camera is owned and initialized by Scene, but Scene doesn't know the aspect
+ratio of the screen, so this will also update the camera with the screen's
+aspect ratio.
+*/
 {
 	Renderer *r = malloc(sizeof(Renderer));
 	r->pixels = pixels;


@@ 325,6 357,7 @@ Renderer *NewRenderer(Pixel *pixels, int width, int height, Camera *camera)
 }
 
 void ClearScreen(Renderer *renderer)
+/* Clears the frame buffer and depth buffer */
 {
 	for (int y = 0; y < renderer->height; y++) {
 		for (int x = 0; x < renderer->width; x++) {


@@ 335,6 368,7 @@ void ClearScreen(Renderer *renderer)
 }
 
 DepthVal *NewDepthBuffer(int width, int height)
+/* Allocates and initializes a depth buffer */
 {
 	DepthVal *values = malloc(sizeof(DepthVal)*width*height);
 	for(int y = 0; y < height; y++) {


@@ 346,6 380,7 @@ DepthVal *NewDepthBuffer(int width, int height)
 }
 
 Camera *NewCamera(double fov, double aspect, double near, double far, Model *model, Physics *physics)
+/* Allocates and initializes a Camera */
 {
 	Camera *camera = malloc(sizeof(Camera));
 	camera->model = model;


@@ 360,16 395,20 @@ Camera *NewCamera(double fov, double aspect, double near, double far, Model *mod
 }
 
 void SetCamera(Camera *camera, double fov, double aspect, double near, double far)
+/* Updates a Camera's properties */
 {
 	camera->fov = fov;
 	camera->aspect = aspect;
-	camera->x_cotan = 1/tan(Rad(fov)/2);
+	camera->x_cotan = 1/tan(Rad(fov)/2); /* precalculated for efficiency */
 	camera->y_cotan = aspect/tan(Rad(fov)/2);
 	camera->near = near;
 	camera->far = far;
 }
 
 Transform CameraTransform(Camera *camera)
+/* Returns the transform to move world vertices into the camera's frame of
+reference, and project them into image space
+*/
 {
 	Transform camera_transform = Identity();
 


@@ 386,16 425,16 @@ Transform CameraTransform(Camera *camera)
 	perspective_transform.m[3][3] = 0;
 	perspective_transform.m[2][3] = (2*camera->far*camera->near) / (camera->far - camera->near);
 	perspective_transform.m[3][2] = -1;
-	// PrintMat(camera_transform);
-	// printf("persp\n");
-	// PrintMat(perspective_transform);
 
 	AddTransform(perspective_transform, &camera_transform);
-// PrintMat(camera_transform);
 	return camera_transform;
 }
 
+// TODO: consider using positive Z-axis & make a special case for the camera
 Transform AlignToAxis(Model *model)
+/* Returns the transform to move vertices into the model's rotational frame of
+reference — the model will be facing the negative Z-axis, and up will be the
+positive Y-axis. Assumes the model is at the origin. */
 {
 	Vector Rx, Ry, Rz;
 	Transform op = Identity();


@@ 416,7 455,9 @@ Transform AlignToAxis(Model *model)
 	return op;
 }
 
+// TODO: test this, seems sus
 Transform Orient(Model *model)
+/* Same as AlignToAxis, but positive Z-axis? I think? */
 {
 	Vector Rx, Ry, Rz;
 	Transform op = Identity();


@@ 438,13 479,16 @@ Transform Orient(Model *model)
 }
 
 void ZoomIn(Camera *camera, double amt)
+/* Updates a Camera's params for a narrower field of view (zoom in) */
 {
 	camera->fov *= 1/(amt/100000 + 1);
 	camera->x_cotan = 1/(camera->aspect * tan(camera->fov/2));
 	camera->y_cotan = 1/tan(camera->fov/2);
 }
+// TODO: also make ZoomOut
 
 Vertex *NewVertex(Vertex *pool)
+/* Creates an uninitialized vertex in a vertex pool */
 {
 	assert(PoolTotal(pool) < MAX_RENDER_VERTICES);
 	Vertex *v = PoolNext(pool);


@@ 452,6 496,7 @@ Vertex *NewVertex(Vertex *pool)
 }
 
 void UpdateScene(Scene *scene, int dt)
+/* Game loop update for a scene—all logical updates for one frame in a scene */
 {
 	int i;
 


@@ 466,7 511,9 @@ void UpdateScene(Scene *scene, int dt)
 	// }
 }
 
+// TODO: rethink how rotation is handled
 void UpdatePhysics(Physics physics, int dt)
+/* Applies Physics updates for a frame—follows Newton's laws */
 {
 	physics.model->position = VecAdd(physics.model->position, VecMul(physics.velocity, dt));
 	physics.velocity = VecAdd(physics.velocity, VecMul(physics.acceleration, dt));


@@ 476,12 523,15 @@ void UpdatePhysics(Physics physics, int dt)
 }
 
 void UpdateParticle(Particle particle, int dt)
+/* Applies physics updates to a particle. Particles don't use the Physics
+component because they don't have rotation, etc */
 {
 	VecAdd(particle.position, VecMul(particle.velocity, dt));
 	VecAdd(particle.velocity, VecMul(particle.acceleration, dt));
 }
 
 void RenderScene(Scene *scene, Renderer *renderer)
+/* Top-level function to render all SceneObjects and Particles in a scene */
 {
 	for (int i = 0; i < PoolTotal(scene->renderable_pool); i++) {
 		Render(scene->renderable_pool[i], renderer);


@@ 492,6 542,7 @@ void RenderScene(Scene *scene, Renderer *renderer)
 }
 
 void DrainRenderPools(Renderer *renderer)
+/* Clears the temporary rendering pools in a Renderer */
 {
 	DrainPool(renderer->vertex_pool);
 	DrainPool(renderer->polygon_pool);


@@ 499,6 550,7 @@ void DrainRenderPools(Renderer *renderer)
 }
 
 void Render(Renderable renderable, Renderer *renderer)
+/* Main rendering pipeline for a mesh. Beware. */
 {
 	int i;
 	int *polygon;


@@ 508,15 560,14 @@ void Render(Renderable renderable, Renderer *renderer)
 	renderMesh.vertices = renderer->vertex_pool;
 	renderMesh.faces = renderer->polygon_pool;
 
+	// TODO: calculate camera transform once per-frame instead
+	/* construct the image transform */
 	Transform mesh_transform = ComposeTransform(
 		CameraTransform(renderer->camera),
 		ModelTransform(renderable.model)
 	);
-	// PrintMat(CameraTransform(renderer->camera));
-	// PrintMat(ModelTransform(renderable.model));
-	// PrintMat(mesh_transform);
 
-	/* model and project all vertices */
+	/* model and project all vertices into image space */
 	for (i = 0; i < PoolTotal(renderable.mesh->vertices); i++) {
 		Vertex *vertex = NewVertex(renderMesh.vertices);
 		*vertex = renderable.mesh->vertices[i];


@@ 527,24 578,13 @@ void Render(Renderable renderable, Renderer *renderer)
 	for (i = 0, polygon = renderable.mesh->faces;
 		 i < PoolTotal(renderable.mesh->faces);
 		 i += NumPolygonVertices(polygon)+1, NextPolygon(polygon)) {
-		// printf("Original polygon:\n");
-		// PrintPolygon(polygon, renderable.mesh->vertices);
-		int *clipped = ClipPolygon(polygon, &renderMesh, renderer);
-		if (NumPolygonVertices(clipped) > 0) {
-			// printf("Polygon %d\n", i);
-			// printf("Original\n");
-			// PrintPolygon(polygon, renderable.mesh->vertices);
-			// printf("Projected\n");
-			// PrintPolygon(polygon, renderMesh.vertices);
-			// printf("Clipped\n");
-			// PrintPolygon(clipped, renderMesh.vertices);
-		}
+		ClipPolygon(polygon, &renderMesh, renderer);
 	}
 
 	/* viewmap all vertices */
 	// TODO: skip clipped vertices
 	for (i = 0; i < PoolTotal(renderMesh.vertices); i++) {
-		Homogenize(renderMesh.vertices[i]);
+		Homogenize(&renderMesh.vertices[i]);
 		CommitTransform(renderer->deviceTransform, &renderMesh.vertices[i]);
 	}
 


@@ 560,7 600,11 @@ void Render(Renderable renderable, Renderer *renderer)
 }
 
 Transform ModelTransform(Model *model)
+/* Returns the transform to move vertices from a model's coordinate space into
+world space
+*/
 {
+	// TODO: figure out this rotation business
 	/* rotate to align up and direction */
 	// Transform t = Orient(model);
 	Transform t = Identity();


@@ 569,6 613,7 @@ Transform ModelTransform(Model *model)
 }
 
 int *NewPolygon(int *pool)
+/* Creates and initializes a 0-gon in a polygon pool */
 {
 	assert(PoolTotal(pool) < MAX_RENDER_POLYGONS);
 	int *polygon = PoolNext(pool);


@@ 577,49 622,44 @@ int *NewPolygon(int *pool)
 }
 
 int *ClipPolygon(int *polygon, Mesh *mesh, Renderer *renderer)
+/* Clips a polygon against a Renderer's clip planes. For each plane, the polygon
+is copied (and clipped) back and forth between the renderer's two polygon pools.
+The temporary polygon is erased each time after it's used to keep memory use low
+*/
 {
 	int *polygonA = NewPolygon(renderer->polygon_pool);
 	int *polygonB = NewPolygon(renderer->alt_polygon_pool);
 
-	// ClipPolygonPlane(polygon, polygonA, mesh, renderer->clip_planes.w_pos, renderer->polygon_pool);
+	// TODO: test which order of clipping these planes is fastest. (probably clip y-neg first, since most of the moon's verts will be below the screen)
 
-// printf("Clipping this polygon:\n");
-// PrintPolygon(polygon, mesh->vertices);
+	// ClipPolygonPlane(polygon, polygonA, mesh, renderer->clip_planes.w_pos, renderer->polygon_pool);
 
-// printf("Clipping on x_neg\n");
 	ClipPolygonPlane(polygon,  polygonB, mesh, renderer->clip_planes.x_neg, renderer->alt_polygon_pool);
-	// ClearPolygon(polygonA, renderer->polygon_pool);
-// PrintPolygon(polygonB, mesh->vertices);
+	// ClearPolygon(polygonA, renderer->polygon_pool); // only for w_pos clipping
 
-// printf("Clipping on x_pos\n");
 	ClipPolygonPlane(polygonB, polygonA, mesh, renderer->clip_planes.x_pos, renderer->polygon_pool);
 	ClearPolygon(polygonB, renderer->alt_polygon_pool);
-// PrintPolygon(polygonA, mesh->vertices);
 
-// printf("Clipping on y_neg\n");
 	ClipPolygonPlane(polygonA, polygonB, mesh, renderer->clip_planes.y_neg, renderer->alt_polygon_pool);
 	ClearPolygon(polygonA, renderer->polygon_pool);
-// PrintPolygon(polygonB, mesh->vertices);
 
-// printf("Clipping on y_pos\n");
 	ClipPolygonPlane(polygonB, polygonA, mesh, renderer->clip_planes.y_pos, renderer->polygon_pool);
 	ClearPolygon(polygonB, renderer->alt_polygon_pool);
-// PrintPolygon(polygonA, mesh->vertices);
 
-// printf("Clipping on z_neg\n");
 	ClipPolygonPlane(polygonA, polygonB, mesh, renderer->clip_planes.z_neg, renderer->alt_polygon_pool);
 	ClearPolygon(polygonA, renderer->polygon_pool);
-// PrintPolygon(polygonB, mesh->vertices);
 
-// printf("Clipping on z_pos\n");
 	ClipPolygonPlane(polygonB, polygonA, mesh, renderer->clip_planes.z_pos, renderer->polygon_pool);
 	ClearPolygon(polygonB, renderer->alt_polygon_pool);
-// PrintPolygon(polygonA, mesh->vertices);
 
 	return polygonA;
 }
 
 void ClipPolygonPlane(int *srcPolygon, int *dstPolygon, Mesh *mesh, Plane clipBoundary, int *polygon_pool)
+/* Sutherland-Hodgeman clipping of a polygon against a plane.
+srcPolygon and dstPolygon both reference vertices in mesh->vertices. Vertices
+are added to the mesh as needed, and v-indices are added to dstPolygon as needed
+*/
 {
 	Vertex *intersection, *current, *previous;
 


@@ 648,13 688,16 @@ void ClipPolygonPlane(int *srcPolygon, int *dstPolygon, Mesh *mesh, Plane clipBo
 	}
 }
 
+// TODO: profile & optimize
 bool VertexInside(Vertex *v, Plane clipBoundary)
+/* Tests whether a vertex is inside a plane. Planes have outward-facing normals */
 {
 	Vector n = clipBoundary.normal;
 	return DotProd4D(n, *v) <= 0;
 }
 
 Vertex ClipIntersect(Vertex *s, Vertex *p, Plane clipBoundary)
+/* Calculates the intersectino of a line segment with a plane */
 {
 	double d1 = DotProd4D(clipBoundary.normal, *s);
 	double d2 = DotProd4D(clipBoundary.normal, *p);


@@ 670,7 713,9 @@ Vertex ClipIntersect(Vertex *s, Vertex *p, Plane clipBoundary)
 // 	// TODO
 // }
 
+// TODO: find a more efficient way to wireframe a mesh without duplicating edges
 void WireframePolygon(int *polygon, Vertex *vertices, Renderer *renderer)
+/* Rasterizes lines between each edge of a polygon */
 {
 	Vertex *current, *previous;
 	previous = LastPolygonVertex(polygon, vertices);


@@ 755,6 800,7 @@ void RasterLineSteep(Vertex a, Vertex b, Color color, Renderer *renderer)
 }
 
 void WritePixel(int x, int y, Color color, Renderer *renderer)
+/* Writes a pixel into a renderer's frame buffer */
 {
 	Pixel p = ColorPixel(color);
 	if (x >= 0 && x < renderer->width && y >= 0 && y < renderer->height) {


@@ 763,12 809,14 @@ void WritePixel(int x, int y, Color color, Renderer *renderer)
 }
 
 Color GetPixel(int x, int y, Renderer *renderer)
+/* Reads a pixel from a renderer's frame buffer */
 {
 	Pixel p = renderer->pixels[(renderer->height - 1 - y)*renderer->width+x];
 	return PixelColor(p);
 }
 
 void WriteDepth(int x, int y, DepthVal value, Renderer *renderer)
+/* Writes a depth value into a renderer's depth buffer */
 {
 	if (x >= 0 && x < renderer->width && y >= 0 && y < renderer->height) {
 		renderer->depthBuffer[(renderer->height - 1 - y)*renderer->width+x] = value;


@@ 776,6 824,8 @@ void WriteDepth(int x, int y, DepthVal value, Renderer *renderer)
 }
 
 bool UpdateDepthBuffer(int x, int y, double z, Renderer *renderer)
+/* Returns whether z is in front of a depth value at an x, y position. Updates
+the depth buffer with the z value if it is in front */
 {
 	if (z > renderer->depthBuffer[y*renderer->width+x]) {
 		renderer->depthBuffer[y*renderer->width+x] = z;


@@ 791,6 841,7 @@ bool UpdateDepthBuffer(int x, int y, double z, Renderer *renderer)
 // }
 
 Model *NewModel(Model *pool)
+/* Creates and initializes a Model */
 {
 	assert(PoolTotal(pool) < MAX_SCENE_OBJECTS);
 	Model *model = PoolNext(pool);


@@ 802,6 853,8 @@ Model *NewModel(Model *pool)
 }
 
 Mesh *NewMesh(void)
+/* Allocates and initializes a Mesh. A Mesh owns a private vertex pool and
+polygon pool to track its vertices and polygons */
 {
 	Mesh *mesh = malloc(sizeof(Mesh));
 	mesh->vertices = NewPool(Vertex, MAX_MESH_VERTICES);

@@ 3,6 3,7 @@
 #include <string.h>
 #include <math.h>
 #include <stdio.h>
+#include <assert.h>
 
 Transform Identity(void)
 {


@@ 50,10 51,10 @@ Transform *NewTransform(void)
 	return t;
 }
 
-Transform FromTransform(Transform transform)
+Transform CloneTransform(Transform transform)
 {
 	int i, j;
-	Transform newTransform = Identity();
+	Transform newTransform;
 	for (i = 0; i < 4; i++) {
 		for (j = 0; j < 4; j++) {
 			newTransform.m[i][j] = transform.m[i][j];


@@ 66,7 67,7 @@ void AddTransform(Transform A, Transform *subject)
 /* combine two transforms that happen in subject, then A order */
 {
 	int i, j, s;
-	Transform B = FromTransform(*subject);
+	Transform B = CloneTransform(*subject);
 
 	for (i = 0; i < 4; i++) {
 		for (j = 0; j < 4; j++) {


@@ 118,7 119,6 @@ Vector ApplyTransform(Transform m, Vector v)
 		m.m[3][2] * v.z +
 		m.m[3][3];
 
-	// printf("w: %f, %f, %f, %f\n", x, y, z, W);
 	result.x = x;
 	result.y = y;
 	result.z = z;


@@ 132,6 132,7 @@ void CommitTransform(Transform t, Vector *v)
 }
 
 Transform RotationX(double angle)
+/* angle in degrees */
 {
 	Transform t = Identity();
 	t.m[1][1] = cos(Rad(angle));


@@ 142,6 143,7 @@ Transform RotationX(double angle)
 }
 
 Transform *RotateX(Transform *t, double angle)
+/* angle in degrees */
 {
 	Transform rotation = RotationX(angle);
 	AddTransform(rotation, t);


@@ 149,6 151,7 @@ Transform *RotateX(Transform *t, double angle)
 }
 
 Transform RotationY(double angle)
+/* angle in degrees */
 {
 	Transform t = Identity();
 	t.m[0][0] = cos(Rad(angle));


@@ 159,6 162,7 @@ Transform RotationY(double angle)
 }
 
 Transform *RotateY(Transform *t, double angle)
+/* angle in degrees */
 {
 	Transform rotation = RotationY(angle);
 	AddTransform(rotation, t);


@@ 166,6 170,7 @@ Transform *RotateY(Transform *t, double angle)
 }
 
 Transform RotationZ(double angle)
+/* angle in degrees */
 {
 	Transform t = Identity();
 	t.m[0][0] = cos(Rad(angle));


@@ 176,6 181,7 @@ Transform RotationZ(double angle)
 }
 
 Transform *RotateZ(Transform *t, double angle)
+/* angle in degrees */
 {
 	Transform rotation = RotationZ(angle);
 	AddTransform(rotation, t);


@@ 183,6 189,7 @@ Transform *RotateZ(Transform *t, double angle)
 }
 
 Transform Rotation(double rx, double ry, double rz)
+/* angle in degrees */
 {
 	Transform t = RotationX(rx);
 	AddTransform(RotationY(ry), &t);


@@ 191,6 198,7 @@ Transform Rotation(double rx, double ry, double rz)
 }
 
 Transform *Rotate(Transform *t, double rx, double ry, double rz)
+/* angle in degrees */
 {
 	Transform rotation = Rotation(rx, ry, rz);
 	AddTransform(rotation, t);


@@ 200,7 208,7 @@ Transform *Rotate(Transform *t, double rx, double ry, double rz)
 Transform Translation(Vector dv)
 {
 	Transform T = Identity();
-	dv = Homogenize(dv);
+	assert(dv.w == 1);
 	T.m[0][3] = dv.x;
 	T.m[1][3] = dv.y;
 	T.m[2][3] = dv.z;


@@ 237,7 245,7 @@ double Determinant(Transform mat)
 	double result;
 
 	n = 4;
-	Transform M = FromTransform(mat);
+	Transform M = CloneTransform(mat);
 
 	for (i = 0; i < n-1; i++) {
 		for (j = i + 1; j < n; j++)

@@ 4,7 4,8 @@
 #include <stdbool.h>
 
 typedef struct Transform {
-	double m[4][4]; // [row][column], and we post-multiply column-vectors
+	/* [row][column], and we post-multiply column-vectors */
+	double m[4][4];
 } Transform;
 
 #define MapRange(v, a0, a1, b0, b1) (((v)-(a0))*((b1)-(b0))/((a1)-(a0))+(b0))


@@ 14,11 15,22 @@ Transform Identity(void);
 void SetIdentity(Transform *m);
 bool IsIdentity(Transform t);
 Transform *NewTransform(void);
-Transform FromTransform(Transform transform);
+
+/* Creates a copy of a transform */
+Transform CloneTransform(Transform transform);
+
+/* Multiplies A into subject as (A · subject) */
 void AddTransform(Transform A, Transform *subject);
+
+/* Multiplies A and B without modifying them, as (A · B) */
 Transform ComposeTransform(Transform A, Transform B);
-Vector ApplyTransform(Transform t, Vector v);
-void CommitTransform(Transform t, Vector *v);
+
+/* Multiplies T to v as (T · v) without modifying */
+Vector ApplyTransform(Transform T, Vector v);
+
+/* Multiplies T into v as (T · v) */
+void CommitTransform(Transform T, Vector *v);
+
 Transform RotationX(double angle);
 Transform *RotateX(Transform *t, double angle);
 Transform RotationY(double angle);

@@ 31,15 31,12 @@ Vector V4D(double x, double y, double z, double w)
   return v;
 }
 
-Vector Homogenize(Vector v4d)
-{
-  Vector v = {
-    v4d.x / v4d.w,
-    v4d.y / v4d.w,
-    v4d.z / v4d.w,
-    1
-  };
-  return v;
+void Homogenize(Vector *v)
+{
+	v->x /= v->w;
+	v->y /= v->w;
+	v->z /= v->w;
+	v->w = 1;
 }
 
 Vector *FromVector(Vector v)


@@ 49,24 46,13 @@ Vector *FromVector(Vector v)
 
 bool VectorEqual(Vector a, Vector b)
 {
-  return fabs(a.x - b.x) < EPSILON &&
-      fabs(a.y - b.y) < EPSILON &&
-      fabs(a.z - b.z) < EPSILON &&
-      fabs(a.w - b.w) < EPSILON;
-}
-
-vIndex FindVertex(Vertex **vertices, Vertex *vertex)
-{
-	int i;
-	for (i = 0; i < list_count(vertices); i++) {
-		if (VectorEqual(*vertices[i], *vertex)) {
-			return i;
-		}
-	}
-	return VERTEX_NOT_FOUND;
+  return
+	fabs(a.x - b.x) < EPSILON &&
+	fabs(a.y - b.y) < EPSILON &&
+	fabs(a.z - b.z) < EPSILON &&
+	fabs(a.w - b.w) < EPSILON;
 }
 
-
 Vector NegVec(Vector v)
 {
 	return V(-v.x, -v.y, -v.z);

@@ 10,7 10,7 @@ typedef struct Vertex {
 	double x, y, z, w;
 } Vector, Vertex;
 
-Vector Homogenize(Vector v4d);
+void Homogenize(Vector *v);
 #define FromVertex(v) FromVector(v)
 Vector *FromVector(Vector v);
 bool VectorEqual(Vector a, Vector b);

@@ 19,7 19,7 @@ void TestFromTransform(void)
 	t.m[2][3] = 3;
 	t.m[0][3] = 9;
 	t.m[2][1] = 7;
-	Transform u = FromTransform(t);
+	Transform u = CloneTransform(t);
 	t.m[2][2] = 0;
 
 	AssertEqual(u.m[2][3], 3);