X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=sobel.frag;h=518b6f8abcdadb4491b8e1187f6cea3e696fa477;hb=485c3c31b1fbb0d2957020c2cb8dc83011bc7b25;hp=9feab1ee6b26ba5c614fd5f0ad2cc920e31f58eb;hpb=968a17613099bde09d83ce570acb35625016cb5e;p=nageru

diff --git a/sobel.frag b/sobel.frag
index 9feab1e..518b6f8 100644
--- a/sobel.frag
+++ b/sobel.frag
@@ -26,25 +26,21 @@ void main()
 	// Computing both directions at once allows us to get away with eight
 	// texture samples instead of twelve.
 
-	float x_left   = tc.x - inv_image_size.x;
-	float x_mid    = tc.x; 
-	float x_right  = tc.x + inv_image_size.x;
+	float top_left     = textureOffset(tex, tc, ivec2(-1,  1)).x;  // Note the bottom-left coordinate system.
+	float left         = textureOffset(tex, tc, ivec2(-1,  0)).x;
+	float bottom_left  = textureOffset(tex, tc, ivec2(-1, -1)).x;
 
-	float y_top    = tc.y + inv_image_size.y;  // Note the bottom-left coordinate system.
-	float y_mid    = tc.y;
-	float y_bottom = tc.y - inv_image_size.y;
- 
-	float top_left     = texture(tex, vec2(x_left,  y_top)).x;
-	float left         = texture(tex, vec2(x_left,  y_mid)).x;
-	float bottom_left  = texture(tex, vec2(x_left,  y_bottom)).x;
+	float top          = textureOffset(tex, tc, ivec2( 0,  1)).x;
+	float bottom       = textureOffset(tex, tc, ivec2( 0, -1)).x;
 
-	float top          = texture(tex, vec2(x_mid,   y_top)).x;
-	float bottom       = texture(tex, vec2(x_mid,   y_bottom)).x;
-
-	float top_right    = texture(tex, vec2(x_right, y_top)).x;
-	float right        = texture(tex, vec2(x_right, y_mid)).x;
-	float bottom_right = texture(tex, vec2(x_right, y_bottom)).x;
+	float top_right    = textureOffset(tex, tc, ivec2( 1,  1)).x;
+	float right        = textureOffset(tex, tc, ivec2( 1,  0)).x;
+	float bottom_right = textureOffset(tex, tc, ivec2( 1, -1)).x;
 
 	gradients.x = (top_right + 2.0f * right + bottom_right) - (top_left + 2.0f * left + bottom_left);
 	gradients.y = (top_left + 2.0 * top + top_right) - (bottom_left + 2.0f * bottom + bottom_right);
+
+	// Normalize so that we have a normalized unit of intensity levels per pixel.
+	gradients.x *= 0.125;
+	gradients.y *= 0.125;
 }