Messages

1

Graphics / Re: Create a light effect with BlendMode?

« on: January 04, 2013, 05:02:03 pm »

Thanks for the reply! It really made things go forward. Though using sf::BlendAdd on the light and sf::BlendMultiply on the scene didn't work.

But I played around with it and came upp with this:

_light.setColor(sf::Color(0, 0, 0, 0));

        _light.setPosition(static_cast<float>(mousePos.x), static_cast<float>(mousePos.y));

//_target is a sf::RenderTexture
        _target.clear(sf::Color(255, 255, 255, 200));

        _target.draw(_light, sf::BlendMultiply);
        //_target.draw(_light, sf::BlendAdd);

        _target.display();


        _pWindow->clear(sf::Color(0, 150, 255, 255));

        _pWindow->draw(_background);

        _darkness.setTexture(_target.getTexture() );

        _pWindow->draw(_darkness, sf::BlendAdd);
        //_pWindow->draw(_darkness, sf::BlendMultiply);

        _pWindow->display();

This works exactley like I want it to. Just one little problem...

The dark isn't that dark. In fact, it's white. My guess was that it was because of
_target.clear(sf::Color(255, 255, 255, 200)); that fill the render texture with a black color.

So I thought switching it to _target.clear(sf::Color(0, 0, 0, 200)); would give me the opposite effect.

But that made the whole render texture invisible!

What am I missing?

*Edit

Nevermind, I solved it

The light was the bad guy. It was also supposed to be black

I'll leave the code here if anyone is intrested.

_light.setColor(sf::Color(255, 255, 255, 0));

        _light.setPosition(static_cast<float>(mousePos.x), static_cast<float>(mousePos.y));

        _target.clear(sf::Color(0, 0, 0, 200));

        _target.draw(_light, sf::BlendNone);

        _target.display();


        _pWindow->clear(sf::Color(0, 150, 255, 255));

        _pWindow->draw(_background);

        _darkness.setTexture(_target.getTexture() );

        _pWindow->draw(_darkness);

        _pWindow->display();

Thanks for the help!

2

Graphics / Create a light effect with BlendMode?

« on: January 04, 2013, 03:40:03 pm »

Hi!

I'm working on a little project and I'm kinda stuck. I'm trying to create a dark screen that you can lit up with a light that follows the mouse.

The effect I'm looking for is something similar to the thing they have in Donkey Kong Country:
http://4.bp.blogspot.com/_PM97N1Dtb10/SjN41jFUNzI/AAAAAAAABRU/UCfF2AfDf2c/s400/torchlight_trouble.jpg

I believe this would be possible by first drawing the background. And then drawing a a compleatly black sprite over the the entire screen, representing the darkness. On top of the darkness sprite I draw a smaller sprite that would be the light.

My thought was that I could use a BlendMode to take the alpha value of the light and "cut through" the darkness. Showing a clear piece of the background.

The code that I have so far is this:

_darkness.setColor(sf::Color(255, 255, 255, 200));
        _light.setColor(sf::Color(0, 0, 0, 0));

        _light.setPosition(static_cast<float>(mousePos.x), static_cast<float>(mousePos.y));

        _pWindow->clear(sf::Color(0, 150, 255, 255));

        _pWindow->draw(_background);

        _pWindow->draw(_darkness);

        _pWindow->draw(_light, sf::BlendMultiply);
       
        _pWindow->display();
 

Am I even on the right track? If so, how can I fix this? If not, what is the right track?

Help is appreciated