By day, she is a personal trainer in Melbourne's western suburbs, and by night (well, after work and on weekends) she is champion cosplayer AltF4.

For the uninitiated, cosplay involves dressing up as characters from films, books and video games - although that seems a prosaic definition of a pastime that is a portal to an underground community, if not an alternate universe.

Her recent creations include Holga Kilgore from Dungeons and Dragons, Chandra from Magic: The Gathering, and the Crystal Maiden from Dota 2.

If these characters are unfamiliar, suffice to say it would be dangerous to mess with them.

AltF4 will be showing off her cosplay at Oz Comic-Con in Melbourne this weekend.

The 32-year-old is completely self-taught and, it almost goes without saying, initially learnt her skills watching YouTube.

Making a good cosplay outfit requires an extensive array of skills. There's sewing, patterning, 3D modelling and printing, sanding, airbrushing, hairdressing and make-up, even EVA foam construction.

"I learnt how to do 15 or 16 different methods of crafting just to make one costume,'' Vander Heyden told AAP.

"It's a mental hobby because there's lots of little hobbies inside one big one."

She discovered the Melbourne cosplay scene almost 10 years ago and was hooked after winning the first competition she entered.

In 2022 AltF4 won the Australian leg of the annual global competition, the Cosplay Central Crown Championships, and went on to represent her country at the finals in Chicago.

However, AltF4 wasn't in green and gold, she was dressed as Vertigo Valorplate from the video game Godfall - a creature resembling an insect with large bug eyes, and wings protruding from her helmet.

(AltF4 prefers cosplay with helmets, because although they restrict vision, there's less bother putting on make-up.)

Cosplay is still a small movement in Australia compared with countries such as the US and Japan, but local competitors are holding their own internationally, according to AltF4.

And the Australian scene is growing, driven by gaming and comic conventions.

"You can have a meet-up with a giant group photo of 300 Spider-Mans - it's really exploded," Vander Heyden said.

While there's the occasional gig with gaming companies, there's still not much money in cosplay, and Vander Heyden is worried that turning her passion into a job might mean she won't enjoy it as much.

For now, AltF4's cosplay is a way to show appreciation of the characters she loves most.

"It's like an open love letter to something that means something to me," she said.

Oz Comic-Con is being held in Melbourne on Saturday and Sunday, before travelling to Canberra, Brisbane, Sydney and Perth.

Australian Associated Press