[21:26:18] [Server thread/ERROR]: SimpleChannelHandlerWrapper exception java.lang.NoClassDefFoundError: javax/vecmath/Matrix4d at mods.flammpfeil.slashblade.entity.EntitySpiralSwords.faceEntityStandby(EntitySpiralSwords.java:297) ~[EntitySpiralSwords.class:?] ...

Doesn't have this issue when playing locally, but get kicked on a server when player tries to middle click and hold mouse. I tried install vecmath jar in my Java installation, but does not work. My server version is 1.7.10 Thermos (also tried Cauldron, and client also gets kicked)

You need to install the Java3D library on the server side.
http://www.oracle.com/technetwork/java/javasebusiness/downloads/java-archive-downloads-java-client-419417.html#java3d-1.5.1-oth-JPR

Thank you for your reply!

I have tried:

• copy the lib folder extracted to /usr/lib/jvm/java-8-oracle/jre (my Java installation destination)
• explicitly set -classpath to contain three jars and -Djava.library.path for libj3dcore-ogl.so on the command line arguments
• set environment of CLASSPATH and LD_LIBRARY_PATH as outlined in README

but none of these worked..

Need package is "vecmath"
Not j3dcore

OK, I added it into libraries/java3d/vecmath/1.5.2/vecmath-1.5.2.jar , and also libraries/javax/vecmath/1.5.2/vecmath-1.5.2.jar, and it still crashes. How should I go about installing vecmath? Thank you for taking the time replying.

OK, I resolved this by modifying Manifest.mf.