Calculate height on Z axis

Bamse · Apr 26th 2023

Hi.

I want to make a function in API to teleport player on location (x,z), let say function teleport_to_surface(x,z). For this i need to calculate a safe Y value so player don't teleport underground or on high and fall to death. So require is to teleport on ground on terrain or if is any building block here, on top of it.

Any can have a idea to accomplish that?

First try was to use function raycastFromWorldPosition(...) but this have serious limitless like chunk when i want to teleport need to be rendered on client side and if teleport far away or on unexplored world .. this approach do not function.

For second try i think to read somehow position of Z direct from chunk data, but here i am stuck i don't have idea how i can do that. Moreover what happen if i want to work with a chunk which was not yet generated by server ...

Thx in advance for hints!

paulevs · Apr 26th 2023

Quote from Bamse

For second try i think to read somehow position of Z direct from chunk data, but here i am stuck i don't have idea how i can do that

Hi, size of blocks in terrain is actually the same as units that player position have (1 block = 1 unit), so you only need to get terrain from specific chunk and iterate it from above until you will find any solid tile (anything with ID greater than 0 - air, and less then 200 - water). Chunk coordinates can be generated from desired position - there is an utility function for that (in ChunkUtils class), or you can divide your position on chunk width and height with flooring the result. Block coordinates inside chunk are relative to chunk position, so their calculation is also not very hard (you need to subtract chunkPos * chunkSize from your absolute block position to get relative position in chunk), and there is also utility function for that.

Quote from Bamse

what happen if i want to work with a chunk which was not yet generated by server

I think that server will just return you null

red51 · Apr 26th 2023

To get the surface lvl at a certain position, you could use the getLODSurfaceLevel() method of the Chunk class - it returns the elevation at a given position, but only takes terrain into account. For example, if you have a particular world position and want to get the surface elevation, you can use the ChunkUtils, as mentioned by paulevs :

Java

//A random target position
Vector3f pos = new Vector3f(2048, 0, 2048);

//Get chunk and block coordinate of that position. First
//create new Vector3i objects to store that...
Vector3i chunkPos = new Vector3i();
Vector3i blockPos = new Vector3i();
//...then calculate the chunk and block coordinates
Utils.ChunkUtils.getChunkAndBlockPosition(pos, chunkPos, blockPos);

//Get chunk (determined by chunk x and z coordinate)
Chunk chunk = World.getChunk(chunkPos.x, chunkPos.z);

//Get lod surface elevation and store it in pos.y
pos.y = chunk.getLODSurfaceLevel(blockPos.x, blockPos.z, true);  // <- true to include water

//Teleport player
player.setPosition(pos);

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Quote from Bamse

Moreover what happen if i want to work with a chunk which was not yet generated by server ...

If the chunk doesn't exist, the server will create a new chunk (but it's only generated into RAM - so unless it gets changed, the server won't save it in the database). So basically the World.getChunk() method never returns null (unless an error occurs). Unfortunately this isn't mentioned in the documentation... we'll change that

Bamse · Apr 26th 2023

Thx red51.

Lol i don't read until late after i figure how to make alone.

BTW i encountered server crash when i try to use function getLODSurfaceLevel()

I will try example from you to see if server still crash when i use function.

So i make something like this:

Quote

/**

* Calculate surface for terrain for x and y coordinates

*

* Note: This function ignore object's from ground level like construction elements and so on!. Just terrain level.

*

* @param x coordinates X

* @param z coordinates Z

* @return Z coordinate - height of terrain surface

*/

public float getSurfaceLevel(float x, float z) {

// calculate chunk position.

int cx=ChunkUtils.getChunkPositionX(x);

int cz=ChunkUtils.getChunkPositionZ(z);

// Calculate block position in chunk

int bx=ChunkUtils.getBlockPositionX(x, cx);

int bz=ChunkUtils.getBlockPositionZ(z, cz);

log.debug(" Global position (x,z): {} {} | Chunk position (x,z) : {} {} | Block position (x,z): {} {}",x,z,cx,cz,bx,bz);

// Get chunk

Chunk chunk= World.getChunk(cx, cz);

// return height (Y axis) including water

// First try: i need only a block so i use function getLODSurfaceLevel() but follow line generate exception unhandled and crash server !

//return chunk.getLODSurfaceLevel(bx, bz, true);

// second try - read all chunk terrain height 32x32

float[] terrain = chunk.getLODTerrain();

// read only block what i need

return terrain[Chunk.getTerrainIndex(bx, bz)];

}

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I tested your code. No crash! Function seems to work properly .

After i tested again my first variant. All worked fine.

I am not sure why earlier test server crashed many time with exception UNCAUGHT ...

Quote

#

# A fatal error has been detected by the Java Runtime Environment:

#

# EXCEPTION_UNCAUGHT_CXX_EXCEPTION (0xe06d7363) at pc=0x00007ffb8fb3cb69, pid=18844, tid=14684

#

# JRE version: OpenJDK Runtime Environment (20.0+36) (build 20+36-2344)

# Java VM: OpenJDK 64-Bit Server VM (20+36-2344, mixed mode, sharing, tiered, compressed oops, compressed class ptrs, g1 gc, windows-amd64)

# Problematic frame:

# C [KERNELBASE.dll+0x2cb69]

#

# No core dump will be written. Minidumps are not enabled by default on client versions of Windows

#

# If you would like to submit a bug report, please visit:

# https://bugreport.java.com/bugreport/crash.jsp

# The crash happened outside the Java Virtual Machine in native code.

# See problematic frame for where to report the bug.

#

--------------- S U M M A R Y ------------

Command Line: -Xmx1024M -Xms32M -Xss1M -XX:MaxDirectMemorySize=256M -XX:-OmitStackTraceInFastThrow

Host: AMD Ryzen 9 5900X 12-Core Processor , 24 cores, 31G, Windows 10 , 64 bit Build 19041 (10.0.19041.2788)

Time: Wed Apr 26 20:57:28 2023 GTB Daylight Time elapsed time: 156.669495 seconds (0d 0h 2m 36s)

--------------- T H R E A D ---------------

Current thread (0x0000023415380520): JavaThread "Thread-0" daemon [_thread_in_native, id=14684, stack(0x000000ad87300000,0x000000ad87400000)]

Stack: [0x000000ad87300000,0x000000ad87400000], sp=0x000000ad873fe6d0, free space=1017k

Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)

C [KERNELBASE.dll+0x2cb69]

C [GameAssembly.dll+0x47a3a0]

C [GameAssembly.dll+0x3a9c3c]

C [GameAssembly.dll+0x3a9d23]

C [GameAssembly.dll+0x44f2f9]

C [GameAssembly.dll+0x16a01c2]

C [GameAssembly.dll+0x2cb1bc]

C 0x0000023403771ff3

Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)

j net.risingworld.api.objects.world.Chunk.getLODSurfaceLevel(IIIIZ)F+0

j net.risingworld.api.objects.world.Chunk.getLODSurfaceLevel(IIZ)F+12

j bamse.rw.HelloWorld.showChunkData(Lnet/risingworld/api/objects/Player;)V+81

j bamse.rw.HelloWorld.keyInput(Lnet/risingworld/api/events/player/PlayerKeyEvent;)V+95

j java.lang.invoke.DirectMethodHandle$Holder.invokeVirtual(Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)V+11 java.base@20

j java.lang.invoke.LambdaForm$MH+0x00000008010bf800.invoke(Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;+52 java.base@20

J 1309 c2 net.jiw.unity.runtime.PluginEventHandler.triggerEvent(Lnet/risingworld/api/events/Event;)Z (388 bytes) @ 0x0000023403f03938 [0x0000023403f02dc0+0x0000000000000b78]

v ~StubRoutines::call_stub 0x000002340375100d

siginfo: EXCEPTION_UNCAUGHT_CXX_EXCEPTION (0xe06d7363), ExceptionInformation=0x0000000019930520 0x000000ad873fe850 0x00007ffae13b9988 0x00007ffade130000

Registers:

RAX=0x00007ffae47f6381, RBX=0x00007ffae13b9988, RCX=0x00007ffae53dc980, RDX=0x00000233804d5d90

RSP=0x000000ad873fe6d0, RBP=0x000000ad873fe9c8, RSI=0x000000ad873fe850, RDI=0x0000000019930520

R8 =0x0000000000000000, R9 =0x00007ffa00000000, R10=0x0000000000000002, R11=0x0000000000000000

R12=0x0000000000000000, R13=0x0000023411055280, R14=0x000000ad873fea10, R15=0x0000023415380520

RIP=0x00007ffb8fb3cb69, EFLAGS=0x0000000000000206

.....

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red51 · Apr 27th 2023

Quote from Bamse

I tested your code. No crash! Function seems to work properly .
After i tested again my first variant. All worked fine.

I am not sure why earlier test server crashed many time with exception UNCAUGHT ...

Hmm... maybe the x or z coordinate was out of bounds? I just realized that the getLODSurfaceLevel() method has no safety checks The game works with native memory here, so if x or z is out of bounds (i.e. < 0 or >= 32), it accesses an invalid memory address which may result in a hard crash...

We'll change that with the next update, so the API will just throw a proper exception then^^

However, if you run into any other crashes (or if the method mentioned above still causes crashes despite using valid indices), please let me know

Bamse · Apr 27th 2023

Quote from red51

Hmm... maybe the x or z coordinate was out of bounds? I just realized that the getLODSurfaceLevel() method has no safety checks The game works with native memory here, so if x or z is out of bounds (i.e. < 0 or >= 32), it accesses an invalid memory address which may result in a hard crash...
We'll change that with the next update, so the API will just throw a proper exception then^^

However, if you run into any other crashes (or if the method mentioned above still causes crashes despite using valid indices), please let me know

For sure that was. i think i messed initially calculate x and y of block position and because that i get out of bounds and game no check and got server crash.

Participate now!