1 files changed, 87 insertions, 0 deletions
diff --git a/src/mbgl/shaders/preludes.cpp b/src/mbgl/shaders/preludes.cpp
new file mode 100644
index 0000000000..a0e9414ceb
--- /dev/null
+++ b/src/mbgl/shaders/preludes.cpp
@@ -0,0 +1,87 @@
+// NOTE: DO NOT CHANGE THIS FILE. IT IS AUTOMATICALLY GENERATED.
+
+#include <mbgl/shaders/preludes.hpp>
+
+namespace mbgl {
+namespace shaders {
+
+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
+
+float evaluate_zoom_function_1(const vec4 values, const float t) {
+    if (t < 1.0) {
+        return mix(values[0], values[1], t);
+    } else if (t < 2.0) {
+        return mix(values[1], values[2], t - 1.0);
+    } else {
+        return mix(values[2], values[3], t - 2.0);
+    }
+}
+vec4 evaluate_zoom_function_4(const vec4 value0, const vec4 value1, const vec4 value2, const vec4 value3, const float t) {
+    if (t < 1.0) {
+        return mix(value0, value1, t);
+    } else if (t < 2.0) {
+        return mix(value1, value2, t - 1.0);
+    } else {
+        return mix(value2, value3, t - 2.0);
+    }
+}
+
+// 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 shaders
+} // namespace mbgl