Add letter grid gimmick

1 files changed, 98 insertions, 0 deletions

diff --git a/disinfo.cginc b/disinfo.cginc
new file mode 100644
index 0000000..faa9489
--- /dev/null
+++ b/disinfo.cginc
@@ -0,0 +1,98 @@
+#include "globals.cginc"
+
+#ifndef __DISINFO_INC
+#define __DISINFO_INC
+
+/*
+ * A small font rendering library.
+ *
+ * Sample usage:
+ *
+ * fixed4 frag(v2f i) : SV_Target
+ * {
+ *   float2 uv = i.uv;
+ *   int2 cell_pos;
+ *   float2 cell_uv;
+ *   float2 res = int2(4, 4);
+ *   if (!getBoxLoc(uv, 0.1, 0.9, res, cell_pos, cell_uv)) {
+ *     return float4(0, 0, 0, 1);
+ *   }
+ *   float2 duv = float2(ddx(i.uv.x), ddy(i.uv.y)) / 4;
+ *   float4 font_color = renderInBox(67, cell_uv, duv);
+ * 
+ *   return font_color;
+ * }
+ */
+
+// Returns false if `uv` does not fall within `bounds`.
+bool remapUVSmaller(float2 uv, float2 bottom_left, float2 top_right,
+    out float2 uvr) {
+  if (!(uv.x > bottom_left.x && uv.x < top_right.x &&
+      uv.y > bottom_left.y && uv.y < top_right.y)) {
+    return false;
+  }
+
+  uvr = uv - bottom_left;
+  uvr = uvr / (top_right - bottom_left);
+
+  return true;
+}
+
+// bounds: the left/right/top/bottom bounds of the inner UV region,
+//     respectively.
+// Always returns true.
+bool remapUVBigger(float2 uv, float2 bottom_left, float2 top_right,
+    out float2 uvr) {
+  uvr = uv * (top_right - bottom_left) + bottom_left;
+
+  return true;
+}
+
+bool getBoxLoc(float2 uv, float2 bottom_left, float2 top_right,
+    int2 res, float padding, out int2 cell_pos, out float2 cell_uv)
+{
+  float2 box_uv;
+  if (!remapUVSmaller(uv, bottom_left, top_right, box_uv)) {
+    return false;
+  }
+
+  // The integer index of the cell pointed to by `uv`, on the interval
+  // [0, res.x - 1] * [0, res.y - 1]
+  cell_pos = fmod(floor(box_uv * res), res);
+
+  float2 box_sz = 1.0 / float2(res);
+  float2 cell_bot_left = (cell_pos - padding) * box_sz;
+  float2 cell_top_right = (cell_pos + 1 + padding) * box_sz;
+  if (!remapUVSmaller(box_uv, cell_bot_left, cell_top_right, cell_uv)) {
+    // This should never happen Clueless
+    return true;
+  }
+
+  return true;
+}
+
+// `c` is a character encoded as ASCII.
+float4 renderInBox(int c, float2 uv, float2 cell_uv, texture2D font, int2 font_res)
+{
+  int letter_idx = c;
+  int2 letter_pos = int2(
+      font_res.x - (letter_idx % font_res.x),
+      letter_idx / font_res.x);
+  letter_pos.x = font_res.x - letter_pos.x;
+  letter_pos.y = (font_res.y - 1) - letter_pos.y;
+  float2 letter_box_sz = 1.0 / float2(font_res);
+  float2 letter_bot_left = letter_pos * letter_box_sz;
+  float2 letter_top_right = (letter_pos + 1) * letter_box_sz;
+  float2 letter_uv;
+  remapUVBigger(cell_uv, letter_bot_left, letter_top_right, letter_uv);
+
+#if 0
+  float4 font_color = font.Sample(linear_clamp_s, letter_uv);
+#else
+  float4 font_color = font.SampleLevel(linear_repeat_s, letter_uv, 0);
+#endif
+  return font_color;
+}
+
+#endif  // __DISINFO_INC
+