Squashed 'external/parallel-rdp/parallel-rdp-standalone/' content from commit 3f59f61f2c

git-subtree-dir: external/parallel-rdp/parallel-rdp-standalone
git-subtree-split: 3f59f61f2c1c56424356003041df5e4a10612049

parallel-rdp/shaders/z_encode.h

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+/* Copyright (c) 2020 Themaister
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef Z_ENCODE_H_
+#define Z_ENCODE_H_
+
+// The Z compression is kind of clever, and uses inverted FP, with more precision close to 1.
+// The compressed Z result is 14 bits, and decompresses to 18-bit UNORM.
+int z_decompress(u16 z_)
+{
+	int z = int(z_);
+	int exponent = z >> 11;
+	int mantissa = z & 0x7ff;
+	int shift = max(6 - exponent, 0);
+	int base = 0x40000 - (0x40000 >> exponent);
+	return (mantissa << shift) + base;
+}
+
+u16 z_compress(int z)
+{
+	int inv_z = max(0x3ffff - z, 1);
+	int exponent = 17 - findMSB(inv_z);
+	exponent = clamp(exponent, 0, 7);
+	int shift = max(6 - exponent, 0);
+	int mantissa = (z >> shift) & 0x7ff;
+	return u16((exponent << 11) + mantissa);
+}
+
+int dz_decompress(int dz)
+{
+	return 1 << dz;
+}
+
+int dz_compress(int dz)
+{
+	return max(findMSB(dz), 0);
+}
+
+#endif