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[dr.crow]

I've recently done the jump from SDL to openGL. And I'm wondering if my old ways of doing things are not the simplest anymore.

What i want to do, is finding a way to implement:
*Zooming
*Ability to support splitscreen

The way i've solved this problem earlier, is by creating a Camera class with the following interface:

Code:

void setCenter(float centerx, float centery);
int getScreenX(float worldx);
int getScreenY(float worldy);
int scale(float v); //convert distance in world space to length on screen
void zoom(float delta);

and then passed a pointer to the camera along to the drawing functions, like this:
gameObject->draw(camera);

This works fine, but I was thinking that there might be a simpler solution involving some opengl functions.
Maybe glViewport or something (but wouldn't that move the gui too?).

How do you guys usually solve this problem?

[Average Software]

I've done split screen in the past with glViewport, and it works just fine.

Assuming an 800x600 window, the algorithm looks something like this:

Code:

glViewport(0, 300, 800, 300); // Set viewport to top half of screen.
DrawPlayer1Scene();
glViewport(0, 0, 800, 300); // Set viewport to bottom half of screen.
DrawPlayer2Scene();
SwapBuffers();

As for zooming, I think it really depends on what you're doing and what you want to zoom in on.  There are many ways to achieve the effect, but I need more information.

[dr.crow]

Thanks for the reply.

As for zooming, I think it really depends on what you're doing and what you want to zoom in on.  There are many ways to achieve the effect, but I need more information.

I mean pressing the plus/minus button on the numpad will cause everything to appear as closer or farther away.

Usually i store a zoomfactor variable inside my cameras.

Code:

int Camera::getScreenX(float worldx){
    return int( (worldx-x)*zoomfactor + w/2);

EDIT:
Found a solution. I didn't quite understand the power of glTranslate and glScale until now.

Here's my camera component if anyone else is interested:

Code:

class CameraComponent:public GameObjectComponent{
    private:
        f32 x,y;
        f32 scale;
    public:
        void update(GameObject* go);
        void recieve(u32 message);
        CameraComponent():x(0.f),y(0.f),scale(10.f){}
};

void CameraComponent::update(GameObject* go){
    x=go->x;
    y=go->y;
}

void CameraComponent::recieve(u32 message){
    switch(message){
        case SETVIEW:
            ///opengl functions
            glLoadIdentity();
            glTranslatef(-x*scale+SCREENWIDTH/2,y*scale+SCREENHEIGHT/2,0.f);
            glScalef(scale,-scale,scale);
        break;
        case ZOOMIN:
            scale+=scale*.3*Time::step;
        break;
        case ZOOMOUT:
            scale-=scale*.3*Time::step;
        break;

    }
}