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1

General / SFML Game Development book problem ( chapter 3 )

« on: August 22, 2014, 03:54:44 pm »

Hi everybody,
I'm currently working on this great book, and i'm having trouble at chapter 3.
Here is the error message :
C:\...\SFML_game_development\src\Aircraft.cpp|16|undefined reference to `ResourceHolder<sf::Texture, Textures::ID>::get(Textures::ID) const'|

I could give you the code but i don't think that's more useful, I also tried with the official code and it still doesn't work...I heard this could be because of my compiler and it's a template issue but i don't know how to fix that at the moment.

Here is my Aircraft.cpp where the error is detected :

#include "Aircraft.h"

#include <SFML/Graphics/RenderTarget.hpp>
#include <SFML/Graphics/RenderStates.hpp>


Textures::ID toTextureID(Aircraft::Type type){
    switch(type){
        case Aircraft::Eagle:
            return Textures::Eagle;
        case Aircraft::Raptor:
            return Textures::Raptor;
    }
}

Aircraft::Aircraft(Type type, const TextureHolder& textures) : mType(type), mSprite(textures.get(toTextureID(type)))
{
    sf::FloatRect bounds = mSprite.getLocalBounds();
    mSprite.setOrigin(bounds.width/2.f, bounds.height/2.f);
}

My header for Aircraft class :

#include <Entity.h>
#include <SFML/Graphics/Sprite.hpp>
#include "ResourceHolder.h"

namespace Textures
{
   enum ID
   {
      Eagle,
      Raptor,
      Desert,
   };
}

template <typename Resource, typename Identifier>
class ResourceHolder;

typedef ResourceHolder<sf::Texture, Textures::ID> TextureHolder;

class Aircraft : public Entity
{
    public:
        enum Type
        {
            Eagle,
            Raptor,
        };
    public:
        Aircraft(Type type, const TextureHolder& textures);
        virtual void drawCurrent(sf::RenderTarget& target, sf::RenderStates states) const;
    protected:
    private:
        Type mType;
        sf::Sprite mSprite;
};

The ResourceHolder.h and ResourceHolder.cpp are the exact same as in https://github.com/SFML/SFML-Game-Development-Book/tree/master/03_World

(but as i said, i also tried to c/p the original code and still doesn't work)

Thanks a lot and sorry for annoying you guys

2

General / Gravity, jump, physics : any advices?

« on: February 01, 2014, 04:30:55 pm »

Hi everybody,
I am interested into the creation of a 2D volley ball game, which as to be as realistic as possible.
In first, i want to create a prototype which allow to :
- display 2 circleshapes ( 1 ball and 1 player )
- player shape is located on the bottom on the screen and we can just make him moving left or right, and jumping by a realistic way( i mean with gravity )
- ball shape spawn in top of screen and fall with gravity; it has also to rebound with player, walls and ground

What I already have:
- player shape which move left or right, and a basic jump implemented:
( i want a real jump so i check on the internet to find equations, i found something like
y=y0 -(1/2*g*t*t) + v*t )

- every collisions test
- rebound against walls

I also have a formula to calculate rebound between two circles but i haven't implemented it at the moment;

So my questions are :
- is it best to use " myObject.move(mySpeed) " or " myObject.setPosition(x,y) " ?
- by trying to implement a realistic jump, i did this :

if(inAir)
               speed.y+=k*grav*clock.getElapsedTime().asSeconds();

where k is a fixed constant,
grav is equal to 9.81

But I have some difficulties with modiying speed.y when the player is on the ground and want to jump...
For example, when do i have to do a clock.restart() ?

Thank you for advance,
Have a good day !