Question

I am looking for a way to achieve a fading effect on an object in an OpenGL ES scene. I want to be able to control the period over which the fading effect takes place.

Can anyone suggest how I might achieve this effect ?

Thanks in advance.

Answer 1

You could update the objects alpha value during the update loop. Gradually decreasing the alpha value a small amount per loop would achieve a fading effect.

To control the period, try using an elapsed value representing the time passed since the last loop along with a calculated coefficient detemined by the time period which you want it to run.

To get the coefficient use something like:
coefficient = (maxAlpha – minAlpha) / fadeTimeInSeconds;

Then in your update loop use something like:
objectsAlpha -= coefficient * timeElapsed

Where timeElapsed is a float representing time passed in seconds since the last update loop.

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I’ve posted this via my phone so sorry for the short answer and not too detailed psuedo code. Also its not specifically opengl.