Coding my game in Blitz2

[r0ber7]

Thank you.

I've now written down a list of things to be done on the code and gfx side.
When I started I was still learning Blitz, so a lot of code had to be rewritten later, and I'm still in that process.
Several things, like the casting menu, haven't made it on that list. Nevertheless, this is the first time I can say that, once these things make it into the game, it will be ready for the masses!

It will be a small world beta test, but I expect it will be fun.

[r0ber7]

Question:

I'm trying to share an array of newtypes in a function.
The newtype is called .obj and the array (objects.obj) holds data for several objects.

Somehow this doesn't work:

maingame.bb

; newtype definition
INCLUDE "obj_newtype.bb"

; object array
objects_n=3
Dim objects.obj(objects_n)

INCLUDE "obj_icheck.bb"

obj_icheck.bb

Function obj_icheck{ obj_i }
SHARED objects
...
If objects(obj_i)\status = 0
...

Tells me "Array not yet Dim'd", when I did do a Dim, except I did it in the maingame.bb, and I'm trying to share it with obj_icheck.bb. I've tried several notations like SHARED objects.obj, SHARED objects(), and so on, but it keeps telling me this. I'm not exactly sure if there's a specific way of sharing arrays of newtypes, so I'm asking for your help, mighty Blitz people.

[Samurai_Crow]

I'm more of a C and AmigaE expert but here's a thought: Maybe you shouldn't be using an array to hold your objects directly. You've already got a type specification for a structure. I'm not sure if Blitz2 supports references to objects but that's got less overhead than passing an array reference and an offset and indexing each time you use an object.

In Assembly it would be implemented as a pointer held in an address register to each structure, then passing the pointer to the specific structure to your obj_icheck so that you're doing the indexing only once.

I hope this helps.

[Graham Humphrey]

For starters if you're going to share arrays, you must include the brackets too - so it'll have to be SHARED objects().

Have you tried not using Includes and just putting all the relevant code into one source file? Maybe, for whatever reason, the compiler just doesn't like you using Includes in this situation, I'm not sure.

[r0ber7]

When I use SHARED objects() the error changes to "Syntax error", relating to:

If objects(obj_i)\status = 0

Yet, before (when it was obj_ball\status) no problem occurred, and I don't see any error in syntax... I'll try throwing everything in one file tomorrow, even though I was trying to avoid doing that.

Thanks for the help.

[r0ber7]

It's working!

I just threw in the Dim in the obj_icheck.bb. Now I can REALLY make everything bounce and slide whenever I want, woohoo!
I've also finally set up a null-modem cable link with my old A1200 so I can test the game on a true original Amiga.

[Graham Humphrey]

Nice work man

I look forward to covering your work in Amiga Future at some point when you're at the stage where people can play it

[r0ber7]

Originally Posted by Graham Humphrey

Nice work man

I look forward to covering your work in Amiga Future at some point when you're at the stage where people can play it

I am honoured.

Meanwhile, I'm coding in some axe throwing. :-)

[r0ber7]

The game is coming along nicely. Start menu and intro are done, and I've added a new enemy and some other stuff too. Now, for my question (as always).

I need help calculating the trajectory of things that get thrown around in a straight line, like fireballs and axes.



B = starting point (start_x, start_y)
A = target (dest_x, dest_y)

Right now I do this: First I calculate the length of the hypotenuse, and determine velocity and set timer to zero.

v = 8.5
t = 0.0
boo = (start_x-dest_x)*(start_x-dest_x)
baa = (start_x-dest_x)*(start_x-dest_x)
hyp = Sqr( boo  + baa )

Then, I do this every Vwait until the object reaches its target.

t = t + 0.5
boo = (dest_x-start_x) * v * t
baa = (dest_y-start_y) * v * t
x = start_x + boo / hyp
y = start_y + baa / hyp

While this works, it eats the CPU. Whenever I launch a fireball and there are more than two moving objects around, the game slows down badly. I'm using quicks, not floats, but that doesn't help much. Could there be a more efficient way of calculating this? I can't calculate before the game launches & throw it in an array either, since the targets are always different.

[Leffmann]

The fastest way is to use an iterative approach and calculate the directional vector and scale its length to that of your velocity, and simply add this vector to the position every frame:

Initialization:

dx = dest_x - pos_x
dy = dest_y - pos_y
scale = velocity / sqrt(dx*dx + dy*dy)
dx = dx*scale
dy = dy*scale

For every image frame:

pos_x = pos_x + dx
pos_y = pos_y + dy

This incurs some slight aliasing, and depending on how many steps are needed to reach the destination and the precision of these quick floats, your target position in the end may be off by a pixel or two.

[r0ber7]

Awesome! It's working, at blazing speed! Thank you, this has been troubling me for a long time.

[r0ber7]

So, I'm at the point that I've put in so much stuff I get out of memory errors.

I have several ideas to get rid of these, some are a bit too code specific to mention here. But, one things bugs me a bit.

There's a start menu. After clicking "play" the game starts. Then after you die or hit escape, you go back to menu. Before the menu loads I do this:

		stopmodule
		for r=0 to 10 : free sprite r : next
		for r=0 to 99 : free shape r :next
		for r=0 to 5 : free bitmap r : next
		for r=0 to 3 : free palette r : next

Yet, for some reason this doesn't free up all memory that was used ingame? How about Displays and Coplists? I just leave them lying around now, cause Free Coplist / Display doesn't work. Either way I'll get around this, I'm just wondering: does Blitz have more functions to clear memory, and how do I use them?

[r0ber7]

Would an array of 640 quicks take up a lot of mem? I have two approaches to ground detection, one involves an array. Is there a way to see which things occupy how much memory?

[r0ber7]

Solved memory problems, I didn't realize Free Coplist was an option. Game is running faster than ever before. I have room to add some spicey stuff I've been planning, it's way too fast now.

[r0ber7]

Ok guys, a quick update.

I've worked on the game a lot the last week and there are only a few things left to add before I can release world 1 as alpha test. There will be 2 gameplay modes. In the first one (adventure) you follow the storyline. In the other one (survival) you blast vikings for points until you die.

Before first release these are left to do:

- a proper "getting hit & dying" procedure for the wizard (right now it's just halfway)
- different ingame music which better suits the atmosphere
- highscores
- fix a few glitches
- test on a real A1200, and in WinUAE (developing in e-uae on linux)

I've added quite a bunch of stuff, which I won't share until first release. :P Also don't expect too much, world 1 isn't very big because it's drawn by hand. Well, by mouse. No random generation of objects or anything. It's an island of 1280x256, but it's big enough to fight vikings on, heh.

The coming two weeks I'll be starting at my new job, so I probably won't have much energy to work on this. Which is why I'm posting this too, just to say, I will release at least this one world in the near future. Seeing how winter is coming, it's quite likely I'll be adding worlds and updating after first release.

So I could say, "expect an alpha release in late september", but I won't because I don't like having a deadline. So no promises. But it'll probably happen anyway.

[whitegiant89]

Sweet cannot wait for a look at the real thing.

[r0ber7]

I've actually been coding in between shifts. I said no deadlines, but hey. If all goes well...

First alpha release: september 11th.

Will be announced in the EAB Gaming Factory.

[Lonewolf10]

Cool. I hope you make your deadline (or thereabouts) as I have the week after that off work. Plenty of time to play your alpha release

(don't worry if you miss your deadline, my demo is 4 months later than planned and still not finished!!)


Regards,
Lonewolf10

[r0ber7]

Originally Posted by Lonewolf10

(don't worry if you miss your deadline, my demo is 4 months later than planned and still not finished!!)

Thank you. But, if I say I'll release then, I will. It might not have everything I want to have in there, but I think it's ready for testing anyway. And besides it's just the first world. I've already got plans for the two worlds after this one, but why wait when the first world is more or less playable. I'll be going Minecraft style, updating now and then with new stuff.

P.S. Considering this is a Coder's Heaven, I'll only post coding related stuff in this thread from now on. Anything else will be in the Game Factory.

[Graham Humphrey]

You got a name for this game yet? Or are you waiting until the 11th before you reveal it?