[solved] - Focus camera on a character

Using Cinder
1

hey,
I creat a video game in 2d and i would like too use a camera,
I want to focus the camera in my character on 2D, but when i draw my character and i use a camera my window don’t display anything.
I draw my character on (0;0;0) and my camera lookAt(0;0;0)
I do wrong ?
thanks you in advance.
Theo

2

Hi,

Could you try using the lookAt method using both eyePoint and target ? For eg:

mCam.lookAt( vec3( camPos, dist ), vec3( camPos, 0.0 ) );
mCam.setPerspective( 60.0f, aspectRatio, 1.0f, 3.0f * dist );

Bala.

3

Hi,

when doing 2D games and graphics, it usually is far easier to simply translate and scale, instead of using a camera. Let your hero wander around freely and just shift and scale the world:

void YourApp::update()
{
    mHeroPosition += mHeroVelocity;   // both are ci::vec2
    mEnemyPosition += mEnemyVelocity; // both are ci::vec2
}

void YourApp::draw()
{
    // store the current model matrix, it will automatically get restored
    gl::ScopedModelMatrix scpModel; 

    // move the world so our hero is always in the center
    // (this will alter the model matrix)
    gl::translate( getWindowCenter() );
    gl::scale( vec2( mZoom ) ); // zoom is a float, defaults to 1
    gl::translate( -mHeroPosition ); // also try mEnemyPosition :)

    // draw our actors
    drawActor( mHeroTexture, mHeroPosition );
    drawActor( mEnemyTexture, mEnemyPosition );

    // scpModel will go out of scope and the model matrix 
    // will be restored
}

void YourApp::drawActor( const ci::gl::Texture2dRef &tex, 
                         const ci::vec2 &pos )
{
    gl::ScopedModelMatrix scpModel;
    gl::translate( pos );
    gl::draw( tex );
}

-Paul

2 Likes
4

Thanks Bala, that what i’ve aleready try to do.

Thanks paul, i will try with your technical it looks nice.
i’ll keep you informed.

5

Here is the result,

51332175_415075042367549_1748199054094893056_n

the problem is that the local landmark of our character is on the top left of this one. How to make it at its center (0,0,0)?
thanks

6

Lots of different ways. One potential way:

void YourApp::drawActor( const ci::gl::Texture2dRef &tex, 
                         const ci::vec2 &pos )
{
    gl::ScopedModelMatrix scpModel;
    gl::translate( pos - ci::vec2 ( tex->getSize() / 2 ) );
    gl::draw( tex );
}

Though it would be best to pass the centred position to drawActor() rather than modifying it internally, just for flexibility reasons.

1 Like
7

thanks so much to all of you for your help. That works !