draw normal shaded sphere

2 files changed, 61 insertions, 16 deletions

diff --git a/src/cl/spirt.cl b/src/cl/spirt.cl
index 26bdf00..e037a38 100644
--- a/src/cl/spirt.cl
+++ b/src/cl/spirt.cl
@@ -13,12 +13,27 @@ GNU General Public License for more details.
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 
-#define RAY_ORIG(RAYS, INDEX) (RAYS[INDEX])
-#define RAY_DIR(RAYS, INDEX) (RAYS[INDEX + 1])
+struct ray {
+	float3 orig;
+	float3 dir;
+};
+
+static float3
+at(const struct ray ray, const float t)
+{
+	return ray.orig + ray.dir * t;
+}
+
+static float
+length_squared(const float3 v)
+{
+	return v.x * v.x + v.y * v.y + v.z * v.z;
+}
 
 __kernel void
-gen_rays(__global float3 *const rays, float3 camera_centre,
-         float3 pixel_delta_u, float3 pixel_delta_v, float3 corner00)
+gen_rays(__global float3 *const rays, const float3 camera_centre,
+         const float3 pixel_delta_u, const float3 pixel_delta_v,
+         const float3 corner00)
 {
 	size_t idx, w, i, j;
 
@@ -29,18 +44,37 @@ gen_rays(__global float3 *const rays, float3 camera_centre,
 
 	idx = (w * j + i) * 2;
 
-	RAY_ORIG(rays, idx) = camera_centre;
-	RAY_DIR(rays, idx) = corner00 +
-	                     ((i * pixel_delta_u) + (j * pixel_delta_v)) -
-	                     camera_centre;
+	rays[idx] = camera_centre;
+	rays[idx + 1] = corner00 + ((i * pixel_delta_u) + (j * pixel_delta_v)) -
+	                camera_centre;
+}
+
+static float
+hit_sphere(const float3 center, const float radius, const struct ray ray)
+{
+	float3 oc;
+	float a, half_b, c, disc;
+
+	oc = ray.orig - center;
+	a = length_squared(ray.dir);
+	half_b = dot(oc, ray.dir);
+	c = length_squared(oc) - radius * radius;
+	disc = half_b * half_b - a * c;
+
+	if (disc < 0.0f)
+		return -1.0f;
+
+	return (-half_b - sqrt(disc)) / a;
 }
 
 __kernel void
-ray_colour(__global uchar *const canvas, __global float3 *const rays)
+ray_colour(__global uchar *const canvas, __global const float3 *const rays)
 {
+	struct ray ray;
+
 	size_t canvas_idx, ray_idx, w, i, j;
-	float3 unit_direction, colour;
-	float a;
+	float3 colour;
+	float t;
 
 	w = get_global_size(0);
 
@@ -50,10 +84,23 @@ ray_colour(__global uchar *const canvas, __global float3 *const rays)
 	canvas_idx = (w * j + i) * 4;
 	ray_idx = (w * j + i) * 2;
 
-	unit_direction = normalize(RAY_DIR(rays, ray_idx));
-	a = 0.5f * (unit_direction.y + 1.0f);
+	ray.orig = rays[ray_idx];
+	ray.dir = rays[ray_idx + 1];
+
+	t = hit_sphere((float3)(0.0f, 0.0f, -1.0f), 0.5f, ray);
+
+	if (t > 0.0) {
+		colour = 0.5f *
+		         (normalize(at(ray, t) - (float3)(0.0f, 0.0f, -1.0f)) +
+		          1.0f);
+	} else {
+		float3 unit_direction;
+		float a;
 
-	colour = (1.0f - a) * (float3)(1.0f) + a * (float3)(0.5f, 0.7f, 1.0f);
+		unit_direction = normalize(ray.dir);
+		a = 0.5f * (unit_direction.y + 1.0f);
+		colour = (1.0f - a) * 1.0f + a * (float3)(0.5f, 0.7f, 1.0f);
+	}
 	colour = 256.0f * clamp(sqrt(colour), 0.0f, 0.999f);
 
 	canvas[canvas_idx] = colour.x;
diff --git a/src/spirt.c b/src/spirt.c
index 527981f..f9c6420 100644
--- a/src/spirt.c
+++ b/src/spirt.c
@@ -302,8 +302,6 @@ main(int argc, char *argv[])
 	img.format = PIXELFORMAT_UNCOMPRESSED_R8G8B8A8;
 	img.mipmaps = 1;
 
-	clFlush(runtime.command_queue);
-
 	InitWindow(opts.width, opts.height, "spirt");
 
 	SetTargetFPS(60);