Post by nexxy in YaruFPS Basic FPS Engine comments

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Hi Yal,

I'm loving the engine and the work you've put into it, thanks!

I have two things I need help with:

-I want to alter the starting position of the bullet so it doesn't always spawn in the center of the screen, and instead I can alter it's starting coordinates so it always spawns at the tip of the gun (so I can move it left/right, up/down relative to screen, so no matter the size of the gun sprite I can always center it at the end of the barrel); I'm at work at the moment so I can't recall the exact names of the scripts but there was one with cx, cy, cz variables that I figured defined the bullet starting position, but no matter how much I played around with them I just couldn't get the desired result.

*The yellow circle is the bullet - I need it to spawn at the very end of the gun barrel*

-Another thing I need helping with is - I can't seem to find where I can set the size of the "level grid", that is, how do I define where is the border of the level itself and where the upper layers of the level begin within the room (I hope this question makes sense).

Any help is greatly appreciated!
Best regards,

Yal7 years ago

First of all, the easy thing: the level grid size is based on the width of the background you use for the level grid. (See the script terrain_flat_to_3d for the details). So basically, if you want a grid that's 2560 pixels wide, use a background that's 2560 pixels wide. Any size should work, but unless it's a multiple of your room grid size it's gonna be hard to keep objects from different layers aligned :P

For the second question... the 3D maths is kinda hard... which is why I skipped that part in the engine :P You'll need to find a reference point (e.g. the player's x, y and zbottom), then find the delta X/Y/Z to the tip of the gun, then spawn the bullet there. If you know the length of all the 'moving parts' (e.g. "spine", "shoulders" and "arm+gun"), you could just compute the X/Y/Z vectors of each part individually and then the tip of the gun should be there.

For each thing...

X coordinate should be lengthdir_x(1,angle against 'forwards')*lengthdir_x(1,angle against 'up')*(length of thing along X axis)
Y coordinate should be lengthdir_y(1,angle against 'forwards')*lengthdir_x(1,angle against 'up')*(length of thing along Y axis)
Z coordinate should be lengthdir_y(1,angle against 'up')*(length of thing along Z axis)

And since the spine is always just Z coordinate and shoulders are always just XY coordinates, this should be possible to simplify a bit. But yeah, it won't really get any easier than this, so guess why games like Wolfenstein and Doom had the gun in the middle so you didn't need to keep track of anything other than the Z coordinate :P

nexxy7 years ago(+1)

Thanks Yal! The "layering" level 3D system is very clever. Regarding the positioning of the bullets - I got that eventually resolved on the GM forum, and you are right - it's very hard and I don't think I'm yet at the level to properly utilize them complex maths and matrices needed for what I'm trying to achieve. So I guess for now I'll just stick with the "gun at the center of the screen"

Cheers!

Yal7 years ago

Sounds like a plan... it's always possible to change it later in case you get better at 3D maths later, and working with 3D is a good way to learn about 3D, I guess :P

IMO the hardest part is figuring out how 3D vectors work (which needs linear algebra so you can actually do math with them - but you need to learn visualizing them as well in order to figure out HOW to use them for any given problem), once you've got that part down you can solve more or less any problem by doodling down a few lines on paper and putting variable names at all angles and lengths you'll need to use in the game. Don't underestimate doodling on paper, it helps visualizing stuff MUCH better than the maths formulae on their own :3

Hobcramwork7 years ago(+1)

Indeed, doodling (& writing) on paper does wonders for me. Good to know that it's helping you out too, Yal :)

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