diff --git a/CMakeLists.txt b/CMakeLists.txt
index e061c73..b7eb995 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,6 +9,7 @@ macro(configure_target target)
 endmacro()
 
 add_library(batomorph
+  src/camera.c
   src/ff.c
   src/obj.c
   src/vec3.c
diff --git a/demo.c b/demo.c
index af02ceb..88d104e 100644
--- a/demo.c
+++ b/demo.c
@@ -1,3 +1,4 @@
+#include "camera.h"
 #include "ff.h"
 #include "obj.h"
 #include "ray.h"
@@ -11,35 +12,23 @@
 #define W 800
 #define H 600
 
-#define VP_H 2.0
-#define VP_W (VP_H * W / H)
-
-#define FOCLEN 1.0
+#define FOCAL_LEN 1.0
+#define VIEWPORT_H 2.0
 
 #define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))
 
-typedef struct {
-	vec3_t centre;
-	double rad;
-} sphere_t;
-
 static const vec3_t lightblue = { 0.4, 0.6, 1.0 };
 static const vec3_t white = { 1.0, 1.0, 1.0 };
 static const vec3_t red = { 1.0, 0.1, 0.2 };
 
-static const vec3_t camera = { 0, 0, 0 };
-static const vec3_t vp_disp = { 0, 0, FOCLEN };
-static const vec3_t vp_u = { VP_W, 0, 0 };
-static const vec3_t vp_v = { 0, -VP_H, 0 };
-static const vec3_t pix_x_step = { VP_W / W, 0, 0 };
-static const vec3_t pix_y_step = { 0, -VP_H / H, 0 };
+static const vec3_t camera_pos = { 0.0, 0.0, 0.0 };
 
 static const obj_t scene[] = {
 	SPHERE(1.0, 0.0, -3.0, 1.0),
 	SPHERE(-2.0, 0.0, -5.0, 1.0),
 };
 
-static pix_t pix[W * H];
+static pix_t pixbuf[W * H];
 
 static vec3_t raycol(ray_t ray)
 {
@@ -63,27 +52,23 @@ static void setpix(vec3_t col, pix_t *out)
 
 int main()
 {
-	img_t img = { .w = W, .h = H, .pix = pix };
-
-	const vec3_t vp_topleft = vec3_sub(
-	    vec3_sub(vec3_sub(camera, vp_disp), vec3_scale(vp_u, 0.5)),
-	    vec3_scale(vp_v, 0.5));
-	const vec3_t pix_orig = vec3_add(
-	    vec3_add(vp_topleft, vec3_scale(pix_x_step, 0.5)),
-	    vec3_scale(pix_y_step, 0.5));
+	img_t img = { .w = W, .h = H, .pix = pixbuf };
+	camera_t camera = camera_init(camera_pos, FOCAL_LEN, VIEWPORT_H, W, H);
 
 	for (unsigned y = 0; y < H; ++y) {
 		fprintf(stderr, "\r[%3d/%3d]", y, H);
 		fflush(stderr);
 
-		const vec3_t row = vec3_add(pix_orig, vec3_scale(pix_y_step, y));
+		const vec3_t row
+		    = vec3_add(camera.pix_origin, vec3_scale(camera.y_step, y));
 		for (unsigned x = 0; x < W; ++x) {
+			const vec3_t pix = vec3_add(row, vec3_scale(camera.x_step, x));
 			const ray_t ray = {
-				.orig = camera,
-				.dir = vec3_unit(vec3_add(row, vec3_scale(pix_x_step, x))),
+				.orig = camera.pos,
+				.dir = vec3_unit(pix),
 			};
 			const vec3_t col = raycol(ray);
-			setpix(col, pix + (W * y + x));
+			setpix(col, img.pix + (W * y + x));
 		}
 	}
 
diff --git a/include/camera.h b/include/camera.h
new file mode 100644
index 0000000..c4d6e0c
--- /dev/null
+++ b/include/camera.h
@@ -0,0 +1,17 @@
+#ifndef CAMERA_H
+#define CAMERA_H
+
+#include "vec3.h"
+
+#include <stdint.h>
+
+typedef struct {
+	vec3_t pos;
+	vec3_t pix_origin, x_step, y_step;
+} camera_t;
+
+camera_t camera_init(
+    vec3_t pos, double focal_len, double viewport_height, uint32_t img_width,
+    uint32_t img_height);
+
+#endif
diff --git a/src/camera.c b/src/camera.c
new file mode 100644
index 0000000..dbd200b
--- /dev/null
+++ b/src/camera.c
@@ -0,0 +1,26 @@
+#include "camera.h"
+
+camera_t camera_init(
+    vec3_t pos, double focal_len, double viewport_height, uint32_t img_width,
+    uint32_t img_height)
+{
+	const double aspect = (double)img_width / (double)img_height;
+	const double viewport_width = viewport_height * aspect;
+	const vec3_t viewport_disp = { 0, 0, focal_len };
+	const vec3_t u = { viewport_width, 0, 0 };
+	const vec3_t v = { 0, -viewport_height, 0 };
+	const vec3_t topleft = vec3_sub(
+	    vec3_sub(pos, viewport_disp), vec3_scale(vec3_add(u, v), 0.5));
+
+	const vec3_t x_step = vec3_scale(u, 1.0 / (double)img_width);
+	const vec3_t y_step = vec3_scale(v, 1.0 / (double)img_height);
+	const vec3_t pix_origin
+	    = vec3_add(topleft, vec3_scale(vec3_add(x_step, y_step), 0.5));
+
+	return (camera_t) {
+		.pos = pos,
+		.pix_origin = pix_origin,
+		.x_step = x_step,
+		.y_step = y_step,
+	};
+}