Visibale Spotlights using Fog

OpenGL Development JOGL Development
#1

Hey there,
i got an design question…

How do i get visible Spotlights in an dark room/enviroment.

Usually, when you are at a gig or show, you see actually the spotlight light with about 30cm length upon the spot itself coz of the smoke in the room.

I was tinking how could it be possible to simulate such an effect without using shaders or particles or other advanced tech.
Maybe you can help me with this.

Lets say, we have an object and setup three lightsources as Spotlights in green, yellow and red.
Could it be possible to archive this goal by using:

void light()
Light-Setup
void fog ()
Fog setup

void display
do the render stuff, draw an object

call fog,
call light
swapBuffers

Could it work in that order or is that far more complicated than i thought?
What do you think?

Best Regards,
nomek

#2

you should be able to simulate the spot light ray with a transparent object using a high alpha 0.8/0.9

#3

Or a particle engine with very low alpha (0.10 or less)

#4

It’s more complicated than you thought :wink:

The above two examples are pretty good ways to achieve what you want. I’d also google about “Volumetric lighting and fog” since that is what you’re trying to do.

The reason it’s not so simple is that the standard lights and fogs in OpenGL only modify the colors of polygons as they’re drawn. So unless you rendered something that looked like the glow, opengl wouldn’t render a glow for you (it’d just light all of the other objects you’ve rendered).