NO BLOCKS are changed with //setbiome (Acacia trees will still be there and will not disappear unless you take them down or replace them)! Even the change to grass color will not be immediately visible! I honestly do not know how long before the change takes effect but it will (I suspect the change is immediate but not visible until after the area is regenerated, you leave then return).
If I am in the center of a desert and "//setbiome jungle" the blocks that are effected remain sand, cacti, whatever!!!
Try it, find a desert, select a 3x3 area then //setbiome jungle.
When nothing visible changes //undo (provided you did nothing after //setbiome) will negate your change.
"//replace sand grass" will cause changes but only in blocks that I selected. Anything below or above my selection will be unaffected!
That doesn't answer my question, because it sets all
the blocks in the selection to plains. I specifically want to change a
biome to another without affecting the rest. So select big area that
contains savanna, beach and oceans and replace only the savanna with plains.
The costly alternative would be using the poly-selection with //sel poly to create a selection that only contains the target biome
NO BLOCKS are changed with //setbiome (Acacia trees will still be there and will not disappear unless you take them down or replace them)!
I know that. You are not understanding my question. I have a bit of Savanna sandwiched between several other biomes (pains, beach, ocean) and I want to change only the Savanna in the selection to plains. This is not about replacing blocks, I am perfectly happy with the actual blocks that are there; I just need to change that Savanna without affecting the surrounding biomes. A selection and //setbiome will change every block inside the selection to the new biome (changing the biome of the block, I am aware it's not the block itself) rather than just Savanna blocks.
TileEntity seems to have understood the problem. If a poly-selection is the only way, then I guess there's no biome mask/filter for //setbiome.
You can right-click (wooden axe) one extreme; left-click the opposite extreme (of the Savanna); then //setbiome plains. Only the area within the right and left clicks will be effected. //setbiome ONLY affects the weather/color of certain blocks NO BLOCKS/ITEMS are changed/replaced!!! There are no brush effects I'm aware of with //setbiome.
You are correct, I cannot visualize why you want to do this, or the reason.
I build a large horse corral on the east side of my base (y = 64). I prefer the grass color offered by the jungle biome. I "//replace whatever grass" (one large square with nothing except grass) was in this area then //setbiome jungle (Ocelots do occasionally spawn there once //setbiome is complete).
A small (21n-s x 11e-w) area immediately to the west of the corral, I modify as a mushroom_island biome. I grow one large red and one large brown mushroom.
I prefer lots of villages and desert temples (not enamored with jungle temples) so the majority of my bases are in or surrounded by deserts.