refactor canvas writing and add proper gamma correction

1 files changed, 15 insertions, 7 deletions

diff --git a/src/cl/spirt.cl b/src/cl/spirt.cl
index e037a38..943f317 100644
--- a/src/cl/spirt.cl
+++ b/src/cl/spirt.cl
@@ -67,12 +67,24 @@ hit_sphere(const float3 center, const float radius, const struct ray ray)
 	return (-half_b - sqrt(disc)) / a;
 }
 
+void
+write_pixel(__global uchar *const pixel, float3 colour)
+{
+	/* gamma correction */
+	colour = 256.0f * clamp(pow(colour, 1.0f/2.2f), 0.0f, 0.999f);
+
+	pixel[0] = colour.x;
+	pixel[1] = colour.y;
+	pixel[2] = colour.z;
+	pixel[3] = 255;
+}
+
 __kernel void
 ray_colour(__global uchar *const canvas, __global const float3 *const rays)
 {
 	struct ray ray;
 
-	size_t canvas_idx, ray_idx, w, i, j;
+	size_t ray_idx, w, i, j;
 	float3 colour;
 	float t;
 
@@ -81,7 +93,6 @@ ray_colour(__global uchar *const canvas, __global const float3 *const rays)
 	i = get_global_id(0);
 	j = get_global_id(1);
 
-	canvas_idx = (w * j + i) * 4;
 	ray_idx = (w * j + i) * 2;
 
 	ray.orig = rays[ray_idx];
@@ -99,12 +110,9 @@ ray_colour(__global uchar *const canvas, __global const float3 *const rays)
 
 		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;
-	canvas[canvas_idx + 1] = colour.y;
-	canvas[canvas_idx + 2] = colour.z;
-	canvas[canvas_idx + 3] = 255;
+	write_pixel(canvas + 4 * (w * j + i), colour);
 }