Let's say I want to go to a certain biome in my world, but its very far. The coordinates are X: 4096 Z: 2048. If I place a portal in the nether at X: 512 Z: 256, will I end up at the biome I wish to travel to or do I have to build a portal in the overworld first?
You will, but it's important to note that portals will always have at least 2 coordinates. Your calculations are correct for one of those coordinates and therefore that spot will be a "perfect portal", but that's not necessarily the case for the other coordinate and entering from that location instead could very well take you hundreds of blocks away from where you intended (this is probably not very likely given there's a portal literally 1 block away).
Thats basically like what I did to reach the Mesa biome in my world, it was 8000 blocks away overworld, so i extended a branch of my nether rail line roughly into the corresponding area and made a portal to take me through. Later on i built a base there and moved the overworld portal to a specific place - can't remember whether that then took me back to the original nether portal i made or created a new one, but whatever, I made sure the nether portal was rebuilt at X 1/8,Z 1/8 of the overworld portal, and completed my nether line to it ...
Yes, the OW reference point for the 512,256 portal in the Nether is 4096, 2048. Game will create a portal in OW somewhere in 33x33 block column centered on this reference point.
Let's say I want to go to a certain biome in my world, but its very far. The coordinates are X: 4096 Z: 2048. If I place a portal in the nether at X: 512 Z: 256, will I end up at the biome I wish to travel to or do I have to build a portal in the overworld first?
You will, but it's important to note that portals will always have at least 2 coordinates. Your calculations are correct for one of those coordinates and therefore that spot will be a "perfect portal", but that's not necessarily the case for the other coordinate and entering from that location instead could very well take you hundreds of blocks away from where you intended (this is probably not very likely given there's a portal literally 1 block away).
Thats basically like what I did to reach the Mesa biome in my world, it was 8000 blocks away overworld, so i extended a branch of my nether rail line roughly into the corresponding area and made a portal to take me through. Later on i built a base there and moved the overworld portal to a specific place - can't remember whether that then took me back to the original nether portal i made or created a new one, but whatever, I made sure the nether portal was rebuilt at X 1/8,Z 1/8 of the overworld portal, and completed my nether line to it ...
Mintutor now works in 1.13!
MrKite & Mc_Etlam ... I salute you!
Thanks for the help, I'm going to start digging out my tunnel.
Yes, the OW reference point for the 512,256 portal in the Nether is 4096, 2048. Game will create a portal in OW somewhere in 33x33 block column centered on this reference point.