I am almost completely un-experienced with mod making, with the most of my knowledge being editing a sprite. I am working on a World Eaters Berserker model based on that Blood Angel/Ultramarine actor mod that was floating around for a while, now my question is, Berserkers often have two raised pieces of metal to either side of their helmet (think horns but straight up) and I have no idea how I could edit the hitbox to accommodate for these pieces.

There's no hitbox in Cortex, it's based on the sprite. I forget which value it is, but inside where you're defining the atomgroup there's a value that defines the density of the atomgroup, or how many atoms the sprite does collision detecting with. Making that atomgroup more dense will increase the accuracy of the collision detection.

Well that's simple enough, thanks for the help!

No problem, happy modding!

Is it possible to make something transparent, but have the hitbox of some sprite?

Maybe, depending on if it's been changed or not.

There WAS a way to do it, and I don't know if it still works.

it has something to do with the color 255,0,255. If I recall correctly it was a glow of that exact color, and shaped right made the things its over invisible (in that shape). Unfortunately this glow has the unfortunate side effect of making absolutely everything it's in front of invisible, even if you don't want it to. At least I'm pretty sure it was with glows. I don't remember it ever getting used very much because it was buggy as hell and didn't always work as expected, and as far as I know it could have been changed in the last, what 1 1/2-2 years? I suggest you make a 'transparent glow.bmp' file with a shape in 255,0,255 and attach it to something and see what happens. make sure intensity is at 100%... I don't remember if it worked in decimals or full numbers. I haven't modded in quite a long time, this is all from memory.