[C SDL] Platform game help
Posted: 17 Mar 2015, 23:26Hello to all, developing a basis for a simple platform game, I encountered some problems in the optimal management of the collisions with the tiles.
Sometimes the player, jumping here and there, remains locked to the ground, and sometimes it didn't collide with tiles at all.
I think this is related to a bad collision detection on Y axis when the player falls, but not sure, and this doesn't happen to much often...
I did a picture of the bug during the play:
To trying to reproduce the bug, just walk and jump around, like the red path in the picture, and soon in a few you try the player will be stuck.
The source code for this example are available here https://sourceforge.net/p/retrogear/code/HEAD/tree/tutorial/platform_movement/.
Collisions for gravity and jumps are handled inside entity.c file, function doEntityGravity().
Player's handling functions are defined inside player.c file, where the gravity and jumping are called.
Tile collisions are handled by tileCollision function, inside tile.c file
This one is a little improved version of this.
If you want to activate the debug mode and see the real player (red block), uncomment this line in entity.c file:
What am I did wrong with this code? Is there a better way to implement gravity and collision checks in this kind of game?
Thanks to all.
Sometimes the player, jumping here and there, remains locked to the ground, and sometimes it didn't collide with tiles at all.
I think this is related to a bad collision detection on Y axis when the player falls, but not sure, and this doesn't happen to much often...
I did a picture of the bug during the play:
To trying to reproduce the bug, just walk and jump around, like the red path in the picture, and soon in a few you try the player will be stuck.
The source code for this example are available here https://sourceforge.net/p/retrogear/code/HEAD/tree/tutorial/platform_movement/.
Collisions for gravity and jumps are handled inside entity.c file, function doEntityGravity().
- {l Code}: {l Select All Code}
void doEntityGravity(Entity *pobj)
{
//Setting entity direction y
if(pobj->vspeed>0)
{
pobj->direction_y = 1;
}
if(pobj->vspeed<0)
{
pobj->direction_y = -1;
}
if(!tileCollision(pobj->x, pobj->y+pobj->vspeed, pobj->w, pobj->h, SOLID, 0))
{
pobj->y+= pobj->vspeed; //Update position
pobj->vspeed+=pobj->gravity; //do gravity
if(pobj->vspeed<0)
{
pobj->status = JUMP;
}
if(pobj->vspeed>0)
{
pobj->status = FALL;
}
if(pobj->vspeed >= TILESIZE) //if the speed is higher than this we might fall through a tile
pobj->vspeed = TILESIZE;
}
//In case of cokku
if(tileCollision(pobj->x, pobj->y+pobj->vspeed, pobj->w, pobj->h, SOLID, 0))
{
if(pobj->vspeed < 0) //Verso l'alto
{
pobj->vspeed = 0.1f; //Cambiamo la direzione della velocità verticale (caduta)
}
if(pobj->vspeed > 0) //Verso il basso
{
pobj->vspeed=1.0f; //Testing the ground
if(pobj->status!=MOVE)
{
pobj->status = STAND;
}
pobj->direction_y = 0;
}
//Sets the entity position nearest to the tile which collide
pobj->y = (pobj->y / TILESIZE)*TILESIZE; //a little fix for small path...
}
}
Player's handling functions are defined inside player.c file, where the gravity and jumping are called.
- {l Code}: {l Select All Code}
void movePlayerDynamic()
{
(...)
/**
* vertical movement
**/
if (curr_gamepad->button_A)
{
curr_gamepad->button_A = 0;
if(!isEntityOnFloor(&Player))
{
printf("Not on floor\n");
return;
}
Player.vspeed = -3.6f; //jump!
}
if (!curr_gamepad->button_A)
{
//if the player isn't jumping already
Player.vspeed+=Player.gravity;
}
doEntityGravity(&Player);
}
Tile collisions are handled by tileCollision function, inside tile.c file
- {l Code}: {l Select All Code}
int tileCollision(int x, int y, int w, int h, int type, unsigned int layer)
{
int i, j;
int minx, miny, maxx, maxy;
//Collision if outside of game field
if (x < 0 || (x + w) > TILESIZE * curr_level->cols ||
y < 0 || (y + h) > TILESIZE * curr_level->rows)
return 1;
// pixel to tiles
minx = x / TILESIZE;
miny = y / TILESIZE;
maxx = (x + w - 1) / TILESIZE;
maxy = (y + h - 1) / TILESIZE;
for (i = minx; i <= maxx ; i++)
{
for (j = miny ; j <= maxy ; j++)
{
if (curr_level->map[layer][j][i]==type)
return 1;
}
}
// No collision
return 0;
}
This one is a little improved version of this.
If you want to activate the debug mode and see the real player (red block), uncomment this line in entity.c file:
- {l Code}: {l Select All Code}
#define DEBUG_GFX
What am I did wrong with this code? Is there a better way to implement gravity and collision checks in this kind of game?
Thanks to all.
