ok so its kinda hard to explain in words so im gonna use screenshots, but im gonna put the screenshots in spoilers cause i have a big monitor so the screenshots are kinda massive. also i didnt think to take screenshots of my process the first time i did this so this is a re-enactment i guess lol

take a screenshot of the video with the textures you want



crop


add some guides, make sure that theyre perfectly square


use GIMP's perspective transform tool. i have no idea how this tool works you just gotta mess with it. line up the edges of the texture with the guides you made in step 3. i usually spend the majority of the time for this whole process on this step. the better you do here, the better the result will be.


step 5 is to crop the image down to the squares you made with your guides but i forgot to take a screenshot of that oops. by default GIMP will snap to guides so unless you turned that off you should be able to just use the rectangle select tool to select the area inside the guides and then just hit "image -> crop to selection"


scale the image down to the proper size. usually this is 16×16 but since im doing 2 textures at once here, one on top of the other, its 16×32


step 7 is to cry because these textures look better than when you did it the first time

step 7 is to mess with the brightness, contrast, hue, and saturation, since the textures in the video are affected by lighting and such. basically just go ham with everything in the "colors" tab until it looks right.


step 8 would be to separate the textures into individual images, if youre doing multiple at once like im doing here. i also forgot to take a screenshot of this but you can just use the rectangle select tool to select one of the textures, then hit ctrl-c, and then go to "file -> create -> from clipboard"


this step isnt entirely necessary, you could just call it done at step 8, but for step 9 i like to go to "image -> mode -> indexed" and convert each individual texture to indexed color with a maximum of 16 colors. this sort of "flattens out" the colors in the image to get rid of some of the weird artifacts that can be introduced by video compression. as a bonus, this also reduces the file size of the completed image!!

im not super experienced with setting up structure generation in datapacks.... the spacing is currently set to 1. while i was messing around with the spawn rates of blue fire, at some point i set it to 0 and the world took like a full 10 minutes to load but the result was beautiful. iirc, spacing of 2 made them a little bit less common then they appear to be in the videos, so i decided to err towards having them be more common so that players wouldnt run out of them. then again, i can see why youd want them to be a little more rare....... ill play around with it!!

also, when you say "spread out" for the glowingflower, do you mean making the groups of them less common, or making the spacing between individual glowingflowers in a group larger? i could totally do the latter just by messing with their base structures a little, but the former runs into the same problem as the bluefire....

i remember that i initially did use mycelium for fakegrass, i dont remember exactly why i switched it to podzol... i think it was because mycelium gives off particles, and the color of the particles didnt match the color of the fakegrass?? thats just something that bugs me.... although i guess it didnt stop me from making redstone wire green with optifine, even though the particles for that are still red......
i hadnt considered how fakegrass would look in a mushroom biome tho!! now if only mushroom biomes also had unique variants of dirt and stone.....