1 files changed, 107 insertions, 0 deletions
diff --git a/src/mbgl/programs/gl/preludes.cpp b/src/mbgl/programs/gl/preludes.cpp
new file mode 100644
index 0000000000..2ca311ebad
--- /dev/null
+++ b/src/mbgl/programs/gl/preludes.cpp
@@ -0,0 +1,107 @@
+// NOTE: DO NOT CHANGE THIS FILE. IT IS AUTOMATICALLY GENERATED.
+#include <mbgl/programs/gl/preludes.hpp>
+
+namespace mbgl {
+namespace programs {
+namespace gl {
+
+const char* vertexPrelude = R"MBGL_SHADER(
+#ifdef GL_ES
+precision highp float;
+#else
+
+#if !defined(lowp)
+#define lowp
+#endif
+
+#if !defined(mediump)
+#define mediump
+#endif
+
+#if !defined(highp)
+#define highp
+#endif
+
+#endif
+
+// Unpack a pair of values that have been packed into a single float.
+// The packed values are assumed to be 8-bit unsigned integers, and are
+// packed like so:
+// packedValue = floor(input[0]) * 256 + input[1],
+vec2 unpack_float(const float packedValue) {
+    int packedIntValue = int(packedValue);
+    int v0 = packedIntValue / 256;
+    return vec2(v0, packedIntValue - v0 * 256);
+}
+
+vec2 unpack_opacity(const float packedOpacity) {
+    int intOpacity = int(packedOpacity) / 2;
+    return vec2(float(intOpacity) / 127.0, mod(packedOpacity, 2.0));
+}
+
+// To minimize the number of attributes needed, we encode a 4-component
+// color into a pair of floats (i.e. a vec2) as follows:
+// [ floor(color.r * 255) * 256 + color.g * 255,
+//   floor(color.b * 255) * 256 + color.g * 255 ]
+vec4 decode_color(const vec2 encodedColor) {
+    return vec4(
+        unpack_float(encodedColor[0]) / 255.0,
+        unpack_float(encodedColor[1]) / 255.0
+    );
+}
+
+// Unpack a pair of paint values and interpolate between them.
+float unpack_mix_vec2(const vec2 packedValue, const float t) {
+    return mix(packedValue[0], packedValue[1], t);
+}
+
+// Unpack a pair of paint values and interpolate between them.
+vec4 unpack_mix_color(const vec4 packedColors, const float t) {
+    vec4 minColor = decode_color(vec2(packedColors[0], packedColors[1]));
+    vec4 maxColor = decode_color(vec2(packedColors[2], packedColors[3]));
+    return mix(minColor, maxColor, t);
+}
+
+// The offset depends on how many pixels are between the world origin and the edge of the tile:
+// vec2 offset = mod(pixel_coord, size)
+//
+// At high zoom levels there are a ton of pixels between the world origin and the edge of the tile.
+// The glsl spec only guarantees 16 bits of precision for highp floats. We need more than that.
+//
+// The pixel_coord is passed in as two 16 bit values:
+// pixel_coord_upper = floor(pixel_coord / 2^16)
+// pixel_coord_lower = mod(pixel_coord, 2^16)
+//
+// The offset is calculated in a series of steps that should preserve this precision:
+vec2 get_pattern_pos(const vec2 pixel_coord_upper, const vec2 pixel_coord_lower,
+    const vec2 pattern_size, const float tile_units_to_pixels, const vec2 pos) {
+
+    vec2 offset = mod(mod(mod(pixel_coord_upper, pattern_size) * 256.0, pattern_size) * 256.0 + pixel_coord_lower, pattern_size);
+    return (tile_units_to_pixels * pos + offset) / pattern_size;
+}
+
+)MBGL_SHADER";
+const char* fragmentPrelude = R"MBGL_SHADER(
+#ifdef GL_ES
+precision mediump float;
+#else
+
+#if !defined(lowp)
+#define lowp
+#endif
+
+#if !defined(mediump)
+#define mediump
+#endif
+
+#if !defined(highp)
+#define highp
+#endif
+
+#endif
+
+)MBGL_SHADER";
+
+} // namespace gl
+} // namespace programs
+} // namespace mbgl