A couple projects ahead of what I'm currently doing right now, I think I'm going to try to make a twin stick shooter in XNA. I.E. you walk with WASD, and shoot with the mouse. And then I realized I don't know how to direct a sprite to the cursor location... Anyway:

1. How do you rotate a sprite to point to the cursor? I don't know much trigonometry, so keep it sorta simple please.

2. Basic lighting effects with XNA? A good 2d tutorial link would be great, and google is turning up nothing. I haven't read much about this.

3. Do you have any suggestions about this tutorial's game state handling?

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Also: Graphics Styles: I've pretty much decided about I what my first large/commercial project to be. I was thinking about the graphics styles and I'd like everyone's opinion.

1. Isometric/2.5d: I have next to no idea how to implement this, but it could end up with very pretty results.

2. 2D-top down; non-tile based: Is this even feasible for say, walking around a large city? Making a map editor for this would be hell... Opinions?

3. 2D-top down; tile-based: This seems like the easiest and most feasible option, but can it look good?
Most of the tile-based games I've seen looked like crap, especially the sci-fi ones (which I'm trying to make).

It'l require some trig to actually do it(easy to find on the net), but the basic logic goes something like this:

1) Get XY of Mouse Cursor
2) Get XY of Sprite
3) Get current angle of sprite
4) Calculate "Vector" between the cursor and sprite's XY (this is where the trig happens)
5) Figure out the difference between the angle your sprite is facing and the vector to the cursor
6) Figure out which direction to turn (i.e. which angle is smaller? Do i turn left 20 degrees or do i turn Right 340 degrees? left of course)
7) Turn sprite

I have an AI routine in my project that performs this kindof tracking. If you're interested, I can pull it out. Or if you'd prefer to figure it out first, thats cool too.



Theres an absolutely SICK lighting 'tutorial' on YouTube but it's anything but basic. You can simulate shadows by drawing the sprite again, offset a bit, black and somewhat transparent.

As for GameState handling, i feel bad but i didnt actually read through that article hehe. I'm experimenting with gamestates at the moment as well. It's amazingly helpfull to be enlightened to the concept of GameStates. What I'd suggest is a case switch statement in your "Update" or "Draw" routines, and they have seperate instructions they carry out based on which gamestate your in. like, case: "MainMenu"... *insert main menu logic here*.. case: "MainGameLoop" *insert main game loop logic here* ETC.



Isometric is just top town 2d with sprite directions (Ne/SW/etc) and some very clever Layer Depth coding. Im not actually sure how its done, never looked into it. But I think the challenge is in working out the layer depths, which change dynamically.



Perfectly feasable. Map editor wouldn't be hell. Before much longer, I'l be writing one for my game. Because everything is viewed in terms of X,Y co-ords, you can generate a MASSIVE map with an actual map file that is incredibly small.



Is your game turn based or real time? If it's turn based, tile-based mapping would be easy. You'd need a multidimensioned array to store which objects/chars are on which tiles. Or more than one array. Well programmatically theres many ways to do it, doesnt matter. If it's real time, tile-based could be very tricky.

Anyways, Hope this helps!

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http://tankzgame.blogspot.com

Its going to be a real-time, sci-fi, action-y shmup thing. I have a few more ideas, but I'm not sure about them yet.
So how do you handle collision detection with option 2? Do you mean, instead of placing tiles, you place different sized objects into a empty map, and then the game handles each object? I don't see how that would make smaller map files.



Could I see the part about vector calculations?
Everything else seems pretty simple.

Yep. If it's tile based, youl have to have some kindof value in your map file for EACH TILE... regardless of how full (or empty it is)... if it's non tile based, all you need to do is have a list of XY coords of the stuff that DOES exist. To put it another way: a 1000 x 1000 tile map with say, 500 objects in it. Your map file would need info for EACH TILE.. (what kindof tile is it, what is on that tile, etc..) thats at least 1,000,500 peices of info.

Now. If it's NON tile based, all you need is 500 peices of info - where the objects are. Much smaller map file.

As for collision detection, there's some tutorials online but basically theres 2 types (Well, 3 i suppose. We'l ignore 'Circular' for now). There's "Rectangular".. which is very fast and efficient, but depending on your sprite artwork, can be somewhat innacurate. Alternatively, there's "Per-Pixel" AKA "Pixel-Perfect" collision detection.. which as the name implies, literally compares pixels to determine collision. While this is 100% accurate, it's fairly CPU heavy. If you've got a ton of sprites all performing pixel perfect collision tests... that can slow things down. If you do want to go pixel perfect, the trick is to perform Rectangular Collision first, on everything.. and ONLY when a rectangular collision happens do you go further and initiate the pixel-perfect test.



Goes a little something like this:



Don't worry about the RadToDeg thing near the end. That just converts from Radians to Degrees. I do it cuz i dont perosnally like seeing radians. All the calculations happen in radians, but i always like to output the result in terms of degrees. Just a personal preference.

_________________
"None are more hopelessly enslaved than those who falsely believe they are free."
"It is no measure of health to be well adjusted to a profoundly sick society."
"Hope is the first step on the road to dissapointment." -Jonah Orion
http://tankzgame.blogspot.com

Very much appreciated, and whenever you get your map editor working, could I have a screenshot for an example?

lol we'l see. I've got a few back-end optomizations to take care of before i go making a map editor. But once i've got one up and running, il post some screenies for sure.

_________________
"None are more hopelessly enslaved than those who falsely believe they are free."
"It is no measure of health to be well adjusted to a profoundly sick society."
"Hope is the first step on the road to dissapointment." -Jonah Orion
http://tankzgame.blogspot.com

This is not quite true. You can simply disregard saving info on empty tiles since they're.. well .. empty.
When loading a map and a tile is empty.. well. guess what happens

It simply depends on your saving routine.



How well your game looks depends entirely on the artist and not entirely on the rendering method. Tiles are just a method to easily place pixel art repetitively throughout the map to simplify work and to not have to hand draw every single one of them.
If you want to see some good tilemaps look at some of the more popular snes games. Seiken Densetsu 3 probably being the most impressive one regarding tilemaps, but there are many other great titles. It is an interesting and fun technology that is easy to handle for collision and pathfinding aswell as map design.

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(googles Seiken Densetsu 3)

Also, how hard would it be to implement a random city system with tile-based graphics?
I.E. You have building templates and the computer creates a city based on slight variations of the templates, and random positioning. (hope I'm making sense) Would it be harder to do with tile graphics or object graphics?

A few problems with that:

a) The tile may not have any mobs/objects on it, but what kindof terrain is it? Grass? Cobblestone? Any other special properties of this otherwise empty tile? That kindof info needs to be saved somewhere.

b) When your draw routine(or any other routine that looks through your tiles) looks at a tile that wasnt instantiated, you'l get null reference errors.

IMO, in a tile based system, 'disregarding' empty tiles is dangerous programming. Every tile in the playable area of your map grid needs to be programmatically mentioned somewhere in your code.

_________________
"None are more hopelessly enslaved than those who falsely believe they are free."
"It is no measure of health to be well adjusted to a profoundly sick society."
"Hope is the first step on the road to dissapointment." -Jonah Orion
http://tankzgame.blogspot.com

Well, I'm not worried about map size massively, since I'm going to use something I call a Point of Interest system . You can only freely visit cities, or places where something will happen. (I.E. Fallout 1) If you try to visit a empty location, 99% of the time, there won't be anything there. And the only sprawling maps will be the ones involved with the main game story.

you can easily define a default tile for empty/undefined in your code. It is not dangerous, it wont be null, because upon loading it gets assigned the default, which can easily be a translucent tile so you only see background images or whatever. It really depends on the project and how you implement it.

But in the end i mostly prefer untiled maps. Although i'm no pixel guy either ;p

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Long pork is people!

wzl's burrow

That's what I meant by 'programmatically mentioning' each tile And unless the entire map is hardcoded into the game, all that info has to sit in a map file.

_________________
"None are more hopelessly enslaved than those who falsely believe they are free."
"It is no measure of health to be well adjusted to a profoundly sick society."
"Hope is the first step on the road to dissapointment." -Jonah Orion
http://tankzgame.blogspot.com

It would not be redundant choose this:
- Write in the map file that the tile is a pointer to a default condition which, by the way, will allocate memory for the tile anyway
than choose this:
- Write in the map file the tile, even if it has nothing, it would be something like "(0, 0)", that will allocate memory for a new tile anyway.

...?

Just my opinion, I think it is best to write the blank tile.

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English is not my native language, so excuse me for any writing mistakes.