diff --git a/demo.c b/demo.c
index cf04dd8..15bd1a5 100644
--- a/demo.c
+++ b/demo.c
@@ -1,27 +1,16 @@
 #include "camera.h"
 #include "ff.h"
 #include "obj.h"
-#include "ray.h"
-#include "vec3.h"
 
-#include <float.h>
-#include <limits.h>
-#include <math.h>
-#include <stdio.h>
 #include <unistd.h>
 
 #define W 800
 #define H 600
-
 #define FOCAL_LEN 1.0
 #define VIEWPORT_H 2.0
 
 #define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))
 
-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_pos = { 0.0, 0.0, 0.0 };
 
 static const obj_t scene[] = {
@@ -32,54 +21,11 @@ static const obj_t scene[] = {
 
 static pix_t pixbuf[W * H];
 
-static vec3_t raycol(ray_t ray)
-{
-	bool got_hit = false;
-	hit_t hit = { .t = DBL_MAX };
-	for (unsigned i = 0; i < NELEMS(scene); ++i) {
-		if (scene[i].intersect(scene[i].params, ray, &hit, 0.0, hit.t))
-			got_hit = true;
-	}
-	if (got_hit)
-		return vec3_scale(vec3_add(hit.normal, white), 0.5);
-
-	const double a = (ray.dir.y + 1.0) / 2.0;
-	return vec3_add(vec3_scale(lightblue, a), vec3_scale(white, 1 - a));
-}
-
-static void setpix(vec3_t col, pix_t *out)
-{
-	out->r = UINT16_MAX * col.x;
-	out->g = UINT16_MAX * col.y;
-	out->b = UINT16_MAX * col.z;
-	out->a = UINT16_MAX;
-}
-
 int main()
 {
-	img_t img = { .w = W, .h = H, .pix = pixbuf };
+	img_t img = { .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(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.pos,
-				.dir = vec3_unit(pix),
-			};
-			const vec3_t col = raycol(ray);
-			setpix(col, img.pix + (W * y + x));
-		}
-	}
-
-	fprintf(stderr, "\r[%3d/%3d]\n", H, H);
-
+	camera_render(&camera, scene, NELEMS(scene), &img);
 	ff_write(STDOUT_FILENO, img);
-
 	return 0;
 }
diff --git a/include/camera.h b/include/camera.h
index c4d6e0c..cf434f5 100644
--- a/include/camera.h
+++ b/include/camera.h
@@ -1,6 +1,8 @@
 #ifndef CAMERA_H
 #define CAMERA_H
 
+#include "img.h"
+#include "obj.h"
 #include "vec3.h"
 
 #include <stdint.h>
@@ -8,10 +10,15 @@
 typedef struct {
 	vec3_t pos;
 	vec3_t pix_origin, x_step, y_step;
+	uint32_t img_width, img_height;
 } camera_t;
 
 camera_t camera_init(
     vec3_t pos, double focal_len, double viewport_height, uint32_t img_width,
     uint32_t img_height);
 
+void camera_render(
+    const camera_t *camera, const obj_t *scene, unsigned scene_count,
+    img_t *img_out);
+
 #endif
diff --git a/src/camera.c b/src/camera.c
index dbd200b..c9c9047 100644
--- a/src/camera.c
+++ b/src/camera.c
@@ -1,5 +1,36 @@
 #include "camera.h"
 
+#include "ray.h"
+
+#include <float.h>
+#include <stdio.h>
+
+static const vec3_t lightblue = { 0.4, 0.6, 1.0 };
+static const vec3_t white = { 1.0, 1.0, 1.0 };
+
+static vec3_t trace(ray_t ray, const obj_t *scene, unsigned scene_count)
+{
+	bool got_hit = false;
+	hit_t hit = { .t = DBL_MAX };
+	for (unsigned i = 0; i < scene_count; ++i) {
+		if (scene[i].intersect(scene[i].params, ray, &hit, 0.0, hit.t))
+			got_hit = true;
+	}
+	if (got_hit)
+		return vec3_scale(vec3_add(hit.normal, white), 0.5);
+
+	const double a = (ray.dir.y + 1.0) / 2.0;
+	return vec3_add(vec3_scale(lightblue, a), vec3_scale(white, 1 - a));
+}
+
+static void setpix(vec3_t col, pix_t *out)
+{
+	out->r = UINT16_MAX * col.x;
+	out->g = UINT16_MAX * col.y;
+	out->b = UINT16_MAX * col.z;
+	out->a = UINT16_MAX;
+}
+
 camera_t camera_init(
     vec3_t pos, double focal_len, double viewport_height, uint32_t img_width,
     uint32_t img_height)
@@ -22,5 +53,34 @@ camera_t camera_init(
 		.pix_origin = pix_origin,
 		.x_step = x_step,
 		.y_step = y_step,
+		.img_width = img_width,
+		.img_height = img_height,
 	};
 }
+
+void camera_render(
+    const camera_t *camera, const obj_t *scene, unsigned scene_count,
+    img_t *img_out)
+{
+	const uint32_t w = img_out->w = camera->img_width;
+	const uint32_t h = img_out->h = camera->img_height;
+
+	for (unsigned y = 0; y < h; ++y) {
+		fprintf(stderr, "\r[%3d/%3d]", y, h);
+		fflush(stderr);
+
+		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->pos,
+				.dir = vec3_unit(pix),
+			};
+			const vec3_t col = trace(ray, scene, scene_count);
+			setpix(col, img_out->pix + (w * y + x));
+		}
+	}
+
+	fprintf(stderr, "\r[%3d/%3d]\n", h, h);
+}