Detecting specific blocks within a specific radius of a point?

[sockpuppetcow]

Hi, I'm rather new to Forge modding and my current project requires me to detect a specific class of block within a certain radius of a player and return boolean. There has got to be a better way than making an individual line for each block in that radius. Anyone know it?

[Jacky2611]

Something like this?:

 

(x, y, z is your center position…)

 

 

for(int x1 = -r; x1 < r; x1++){

            for(int y1 = -r; y1 < r; y1++){

                    for(int z1 = -r; z1 < r; z1++){                                   

                            double dist = MathHelper.sqrt_double((x1*x1 + y1*y1 + z1*z1)); //Calculates the distance

                            if(dist > r)

                                    continue;

 

                            Block blockatcords = world.getBlock(x+x1, y+y1, z+z1);

if(blockatcords==XXXXX){DO SOMETHING}

                    }

            }

}

 

 

I don't have the time to test it, but if this works could you please press the thankyou button?

 

[jabelar]

I don't know if performance is a big issue, but since you're only trying to find out if there is at least one of the block in the whole radius, you can quit the search as soon as you find one so I would probably use a "labeled break" to get out of Jacky2611's loops once I found the first occurrence. 

 

To understand how you can use a "labeled break" to get out of nested loops in Java, refer to first answer to this question: http://stackoverflow.com/questions/886955/breaking-out-of-nested-loops-in-java

 

While some argue that breaks are evidence of a unstructured coding style, I think they have their place in performance optimization.

 

Anyway, I don't think you should continue to check hundreds of block locations after you find one...

[coolAlias]

  On 4/2/2014 at 9:59 PM, Jacky2611 said:

Something like this?:

 

(x, y, z is your center position…)

 

 

for(int x1 = -r; x1 < r; x1++){

            for(int y1 = -r; y1 < r; y1++){

                    for(int z1 = -r; z1 < r; z1++){                                   

                            double dist = MathHelper.sqrt_double((x1*x1 + y1*y1 + z1*z1)); //Calculates the distance

                            if(dist > r)

                                    continue;

 

                            Block blockatcords = world.getBlock(x+x1, y+y1, z+z1);

if(blockatcords==XXXXX){DO SOMETHING}

                    }

            }

}

 

 

I don't have the time to test it, but if this works could you please press the thankyou button?

You can use the initial x/y/z coordinates as the starting and ending points of the for loops and there is no need to check the distance. Performing a sqrt operation every iteration increases the performance cost significantly.

[TheGreyGhost]

Hi

 

a couple of suggestions

 

Don't take square root, calculate the SquaredDistance first and compare to that instead.  Much faster.

 

If you are searching for Blocks that have a TileEntity, you can find them much faster by first calling WorldServer.getAllTileEntityInBox, and then iterating through the list, discarding any which are further away from you than your search radius.  This will let you use a much bigger search radius without causing horrible lag.

 

(Re WorldServer: usually you will be given a World, and you can check if it's a WorldServer using .isRemote - if it returns false, you're on the server.)

 

-TGG

 

 

[jabelar]

  On 4/3/2014 at 3:53 AM, coolAlias said:

there is no need to check the distance.

 

Well there is if the OP actually wants to check for actual radius (i.e. a sphere) rather than a box.  If you don't check distance you'd be checking in a big cube, but the way he worded the original question made it sound like he wanted a big sphere.  Of course if it doesn't matter much then yes a big cube is easier.

[coolAlias]

  On 4/3/2014 at 2:30 PM, jabelar said:

  Quote

there is no need to check the distance.

 

Well there is if the OP actually wants to check for actual radius (i.e. a sphere) rather than a box.  If you don't check distance you'd be checking in a big cube, but the way he worded the original question made it sound like he wanted a big sphere.  Of course if it doesn't matter much then yes a big cube is easier.

Ah, if that is indeed what the OP meant, then you'd be right After playing with Minecraft code long enough, I've started to associate "radius" with cubes

 

@OP If that's the case, you should follow TGG's advice and compare distance squared against the squared radius, rather than using square roots; if that's not the case, then the check is wholly unnecessary.

[sockpuppetcow]

Okay let's see if I can answer everyone at once here...

I need the function to return a boolean if there is any amount of the block at all, so just finding one will work. I think doing a cube setup would end up causing false-positives in some cases because that would cover a bigger area than the actual 16 or so block radius that I need to search in (so I'm looking in a sphere here). Given that, I guess I'll go with jabelar and TGG's advice and see where that gets me. I'll come back and let you know what happens.