Add document for compressed network values

src/items/attachment.hpp

@@ -88,7 +88,7 @@ private:
     /** Time left till attachment expires. */
     int16_t         m_ticks_left;
 
-    /** For parachutes only, rounded down to 2 digits for network. */
+    /** For parachutes only, stored in cm/s for networking. */
     int16_t         m_initial_speed;
 
     /** For zoom-in animation */

src/items/flyable.cpp

@@ -444,7 +444,7 @@ bool Flyable::updateAndDelete(int ticks)
 
     if(m_has_hit_something) return true;
 
-    // Round down values in network for better synchronization
+    // Round values in network for better synchronization
     if (NetworkConfig::get()->roundValuesNow())
         CompressNetworkBody::compress(m_body.get(), m_motion_state.get());
     // Save the compressed values if done in client

src/network/compress_network_body.hpp

@@ -29,11 +29,12 @@ namespace CompressNetworkBody
 {
     using namespace MiniGLM;
     // ------------------------------------------------------------------------
-    inline void setRoundedDownValues(float x, float y, float z,
+    /** Set body and motion state of bullet object with compressed values. */
-                                     uint32_t compressed_q,
+    inline void setCompressedValues(float x, float y, float z,
-                                     short lvx, short lvy, short lvz,
+                                    uint32_t compressed_q,
-                                     short avx, short avy, short avz,
+                                    short lvx, short lvy, short lvz,
-                                     btRigidBody* body, btMotionState* ms)
+                                    short avx, short avy, short avz,
+                                    btRigidBody* body, btMotionState* ms)
     {
         btTransform trans;
         trans.setOrigin(btVector3(x,y,z));
@@ -49,8 +50,15 @@ namespace CompressNetworkBody
         body->setInterpolationLinearVelocity(lv);
         body->setInterpolationAngularVelocity(av);
         body->updateInertiaTensor();
-    }   // setRoundedDownValues
+    }   // setCompressedValues
     // ------------------------------------------------------------------------
+    /** Compress transformation and velocities of bullet object, it will
+     *  call MiniGLM::compressQuaternion for compress quaternion of
+     *  transformation and convert linear and angular velocities to half floats
+     *  it can be used by client to locally round values to make sure client
+     *  and server have similar state when saving state if you don't provoide
+     *  bns.
+     */
     inline void compress(btRigidBody* body, btMotionState* ms,
                          BareNetworkString* bns = NULL)
     {
@@ -65,9 +73,9 @@ namespace CompressNetworkBody
         short avx = toFloat16(body->getAngularVelocity().x());
         short avy = toFloat16(body->getAngularVelocity().y());
         short avz = toFloat16(body->getAngularVelocity().z());
-        setRoundedDownValues(x, y, z, compressed_q, lvx, lvy, lvz, avx, avy,
+        setCompressedValues(x, y, z, compressed_q, lvx, lvy, lvz, avx, avy,
             avz, body, ms);
-        // if bns is null, it's locally compress (for rounding down values)
+        // if bns is null, it's locally compress (for rounding values)
         if (!bns)
             return;
 
@@ -76,6 +84,7 @@ namespace CompressNetworkBody
             .addUInt16(avx).addUInt16(avy).addUInt16(avz);
     }   // compress
     // ------------------------------------------------------------------------
+    /* Called during rewind when restoring data from game state. */
     inline void decompress(const BareNetworkString* bns,
                            btRigidBody* body, btMotionState* ms)
     {
@@ -89,7 +98,7 @@ namespace CompressNetworkBody
         short avx = bns->getUInt16();
         short avy = bns->getUInt16();
         short avz = bns->getUInt16();
-        setRoundedDownValues(x, y, z, compressed_q, lvx, lvy, lvz, avx, avy,
+        setCompressedValues(x, y, z, compressed_q, lvx, lvy, lvz, avx, avy,
             avz, body, ms);
     }   // decompress
 };

src/physics/physical_object.cpp

@@ -633,7 +633,7 @@ void PhysicalObject::update(float dt)
 {
     if (!m_is_dynamic) return;
 
-    // Round down values in network for better synchronization
+    // Round values in network for better synchronization
     if (NetworkConfig::get()->roundValuesNow())
         CompressNetworkBody::compress(m_body, m_motion_state);
 

src/utils/mini_glm.hpp

@@ -568,6 +568,12 @@ namespace MiniGLM
         return compressVector3(tangent) | 1 << 30;
     }   // quickTangent
     // ------------------------------------------------------------------------
+    /** Round and save compressed values (optionally) btTransform.
+     *  It will round with 2 digits with min / max +/- 2^23 / 100 for origin in
+     *  btTransform and call compressQuaternion above to compress the rotation
+     *  part, if compressed_data is provided, 3 24 bits and 1 32 bits of
+     *  compressed data will be written in an int[4] array.
+     */
     inline void compressbtTransform(btTransform& cur_t,
                                     int* compressed_data = NULL)
     {