初始提交: UE5.3项目基础框架

Plugins/CesiumForUnreal/Source/ThirdParty/include/CesiumUtility/AttributeCompression.h

@@ -0,0 +1,82 @@
+#pragma once
+
+#include "Library.h"
+#include "Math.h"
+
+#include <glm/glm.hpp>
+
+namespace CesiumUtility {
+/**
+ * @brief Functions to handle compressed attributes in different formats
+ */
+class CESIUMUTILITY_API AttributeCompression final {
+
+public:
+  /**
+   * @brief Decodes a unit-length vector in 'oct' encoding to a normalized
+   * 3-component vector.
+   *
+   * @param x The x component of the oct-encoded unit length vector.
+   * @param y The y component of the oct-encoded unit length vector.
+   * @param rangeMax The maximum value of the SNORM range. The encoded vector is
+   * stored in log2(rangeMax+1) bits.
+   * @returns The decoded and normalized vector.
+   */
+  template <
+      typename T,
+      class = typename std::enable_if<std::is_unsigned<T>::value>::type>
+  static glm::dvec3 octDecodeInRange(T x, T y, T rangeMax) {
+    glm::dvec3 result;
+
+    result.x = CesiumUtility::Math::fromSNorm(x, rangeMax);
+    result.y = CesiumUtility::Math::fromSNorm(y, rangeMax);
+    result.z = 1.0 - (glm::abs(result.x) + glm::abs(result.y));
+
+    if (result.z < 0.0) {
+      const double oldVX = result.x;
+      result.x =
+          (1.0 - glm::abs(result.y)) * CesiumUtility::Math::signNotZero(oldVX);
+      result.y =
+          (1.0 - glm::abs(oldVX)) * CesiumUtility::Math::signNotZero(result.y);
+    }
+
+    return glm::normalize(result);
+  }
+
+  /**
+   * @brief Decodes a unit-length vector in 2 byte 'oct' encoding to a
+   * normalized 3-component vector.
+   *
+   * @param x The x component of the oct-encoded unit length vector.
+   * @param y The y component of the oct-encoded unit length vector.
+   * @returns The decoded and normalized vector.
+   *
+   * @see AttributeCompression::octDecodeInRange
+   */
+  static glm::dvec3 octDecode(uint8_t x, uint8_t y) {
+    constexpr uint8_t rangeMax = 255;
+    return AttributeCompression::octDecodeInRange(x, y, rangeMax);
+  }
+
+  /**
+   * @brief Decodes a RGB565-encoded color to a 3-component vector
+   * containing the normalized RGB values.
+   *
+   * @param value The RGB565-encoded value.
+   * @returns The normalized RGB values.
+   */
+  static glm::dvec3 decodeRGB565(const uint16_t value) {
+    constexpr uint16_t mask5 = (1 << 5) - 1;
+    constexpr uint16_t mask6 = (1 << 6) - 1;
+    constexpr float normalize5 = 1.0f / 31.0f; // normalize [0, 31] to [0, 1]
+    constexpr float normalize6 = 1.0f / 63.0f; // normalize [0, 63] to [0, 1]
+
+    const uint16_t red = static_cast<uint16_t>(value >> 11);
+    const uint16_t green = static_cast<uint16_t>((value >> 5) & mask6);
+    const uint16_t blue = value & mask5;
+
+    return glm::dvec3(red * normalize5, green * normalize6, blue * normalize5);
+  };
+};
+
+} // namespace CesiumUtility