Add an effect to do re-slicing of the image, for overlap/discard.

[movit] / slice_effect.frag

diff --git a/slice_effect.frag b/slice_effect.frag
new file mode 100644 (file)
index 0000000..8416515
--- /dev/null
+++ b/slice_effect.frag
@@ -0,0 +1,26 @@
+uniform float PREFIX(output_coord_to_slice_num);
+uniform float PREFIX(slice_num_to_input_coord);
+uniform float PREFIX(slice_offset_to_input_coord);
+ 
+vec4 FUNCNAME(vec2 tc) {
+       // DIRECTION_VERTICAL will be #defined to 1 if we are expanding vertically,
+       // and 0 otherwise.
+#if DIRECTION_VERTICAL
+       float sliced_coord = tc.y;
+#else
+       float sliced_coord = tc.x;
+#endif
+
+       // Find out which slice we are in, and a 0..1 coordinate for the offset within that slice.
+       float slice_num = floor(sliced_coord * PREFIX(output_coord_to_slice_num));
+       float slice_offset = fract(sliced_coord * PREFIX(output_coord_to_slice_num));
+
+       // Find out where this slice begins in the input data, and then offset from that.
+       float input_coord = slice_num * PREFIX(slice_num_to_input_coord) + slice_offset * PREFIX(slice_offset_to_input_coord);
+
+#if DIRECTION_VERTICAL
+       return INPUT(vec2(tc.x, input_coord));
+#else
+       return INPUT(vec2(input_coord, tc.y));
+#endif
+}