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2d animations

Started by Ninj4D4n Jan 23, 2003 at 4:15 PM 2 replies 1.3k views

Original Post

Jan 23, 2003 at 4:15 PM

Hey all, just a quick question, but how are some ways that people have handled 2d animation in a game?? i''m not talking about moving a bitmap around.... but moving an animated bitmap around, like when a character walks. Do people use a special file format? circular lists? Just curious to see how people are doing this. --Thanks Ninj4D4n

fisheyel83l

Jan 23, 2003 at 4:35 PM

I''m using one image file to store all the sprites next to each other. I have a sprite class that accepts arguments such as: sprite size (width and height), number of sprites, etc. This way the class can figure out how to index the sprites itself, so bounds aren''t exceeded. I also have a class for a "Character" object, which has an instance of the sprite class as a member variable. In this "Character" class, I define certain animation variables, such as walkStart = 10, walkEnd = 16, etc. The numbers correspond to cells of animation in the sprite class, effectively allowing the character class to calculate how to loop through the walking animation, or any other animation I define constants for. This way, the image files can differ if I want them to--I can make walking animations begin at cell 12 for one character and 10 for another. This is convenient because some characters don''t need to have as many animations as other (i.e. a trivial dog "character" walking vs. the human lead character walking. I''d want the human to have more walking frames than the dog, so his movement could be more detailed. ) Anyway, hope this helps. If anyone wants to suggest some improvements on MY style, please go ahead. This is my first time writing game code.

thehurricane

Jan 23, 2003 at 4:40 PM

Here''s how I''m handling sprite animation for my 2D sidescroller:

First off define a FRAME class, used to hold each frame of animation. It just consists of the image and a delay value for how long it will take until the next frame.

  class FRAME
{
public:
	ZImage *img;
	double delay;
};

Then for each monster/baddie/sprite type define a new CspriteInfo class like this:

  class CspriteInfo  
{
public:
	void unLoad();
	CspriteInfo();
	virtual ~CspriteInfo();

	ZImage *images;
	list<FRAME> *anims;
	int numImages;
};

Then I have a Csprite class for each INSTANCE of the sprites. This holds the monster''s position and state. The Csprite class has a static array of CspriteInfo''s for each monster type. This means that the actual images and animations for each monster type will not be loaded and allocated a place in memory for each individual monster on screen--I can put 10,000 baddies on screen, as long as there are a limited number of types.

  class Csprite : public CsceneItem
{
public:

	Csprite();
	Csprite(int idInit, int x, int y, int angleInit, int rotVelInit);
	virtual ~Csprite();

	virtual void process();
	virtual void draw();
	void setAnim(int n);
	void doAnim();
	ZImage* getImage();

	static CspriteInfo* spriteData;
	static int numSprites;
	static int spriteCount;

	static void unLoadInfo();
	static void addSpriteInfo(char * filename);
	static void loadImages(int spriteId, int numImages, char *fileName,int r,int g, int b);

private:
	int id;
	int currentImage;
	list<FRAME>::iterator currentFrame;

	int currentAnim;// which animation is current looping

	int oldTime;	// used for timing animation


	double angle;	// angle to draw at

	double rotVel;	// rotating velocity

	POINTD_ pos;
	bool deleteFlag;
	
};

The Csprite::doAnim() function looks like this:

  void Csprite::doAnim()
{
	ZEngine *ze = ZEngine::GetInstance();
	
	// see if we need to advance animation

	if ( ze->GetTime() - oldTime > currentFrame->delay )
	{
		currentFrame++;
		if (currentFrame == spriteData[id].anims[currentAnim].end())
			currentFrame = spriteData[id].anims[currentAnim].begin();

		oldTime = ze->GetTime();
	}

}

So currentFrame is the key to the whole thing--its an STL list iterator, and it makes the sprite''s draw function REALLY easy. Each ZImage structure has Draw and DrawRotated functions, so:

  void Csprite::draw()
{
       currentFrame->img->DrawRotated(pos.x,pos.y,angle);
}

Ninj4D4n

Jan 23, 2003 at 10:08 PM

thanks,

That''s very helpful, so apparently there''s no magical sprite animation file, its up to me to make the images change accordingly. If anyone else has some input as to how they handle this, it would help alot. Thanks again thehurricane and fisheyel83l.

--Ninj4D4n

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