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OpenGL How to have more than 8 spotlights

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How must I do to have more than 8 spotlights in opengl?


glLightfv(GL_LIGHT0,GL_SPECULAR,luceSpeculare);
glEnable(GL_LIGHT0);
glLightf(GL_LIGHT0,GL_SPOT_CUTOFF,60.0f);
glLightfv(GL_LIGHT0,GL_POSITION,posizioneLampione0);
glLightfv(GL_LIGHT0,GL_SPOT_DIRECTION,direzioneLuceGiu);
...
...
...
glLightfv(GL_LIGHT7,GL_SPECULAR,luceSpeculare);
glEnable(GL_LIGHT7);
glLightf(GL_LIGHT7,GL_SPOT_CUTOFF,60.0f);
glLightfv(GL_LIGHT7,GL_POSITION,posizioneLampione7);
glLightfv(GL_LIGHT7,GL_SPOT_DIRECTION,direzioneLuceGiu);


I need more than 8 spotlight.

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There are a few options. You can do multipass rendering, which basically means drawing your geometry more than once and each time you set 8 different lights and accumulate the result. Another couple of options are to use deferred or light-pre-pass rendering techniques.

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Quote:
Original post by Dave
There are a few options. You can do multipass rendering, which basically means drawing your geometry more than once and each time you set 8 different lights and accumulate the result. Another couple of options are to use deferred or light-pre-pass rendering techniques.


can you do a simply example, please?
i don't understand very well because i don't speak english very good...
thank you!!!

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1) Get the first 8 lights and draw the object as normal.
2) Disable ambient lighting, and enable additive blending.
3) Render the object again with the next 8 lights.
4) If there's more lights remaining, go to step 3.
5) Enable ambient lighting, and disable additive blending.

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Quote:
Original post by Hodgman
1) Get the first 8 lights and draw the object as normal.
2) Disable ambient lighting, and enable additive blending.
3) Render the object again with the next 8 lights.
4) If there's more lights remaining, go to step 3.

can you do an example with code?

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Another option, if you don't need all the lights all the time is to group them up.

For each Object
-collect upto the 8 light sources that affect this object
-glEnable and glLightf the parameters for the lights you found
-disable any extra lights if your object has less that 8 sources
-draw your object

The hard part of this is figuring out what lights you may need. Take a look at the OpenGl Redbook for the equations used for lighting. You can use each light's spot exponent and attenuation factor to determine the maximum effective range of that light. So, when collecting the list of lights for an object, you check to see what lights are most going to affect the object based on range. This way you only render each object once.

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Quote:
can you do an example with code?
Writing up a working code example for this would be non-trivial and could take quite a while. Maybe you'll get lucky and someone will do it for you, but I think it's unlikely.

A better bet would probably be to try and code it yourself, and then post back here if you run into problems. Unfortunately, dealing with multiple lights can get kind of complicated no matter how you approach it. I'll also mention that although you can probably get away with using the fixed-function pipeline for this, these days most people's efforts are focused on shader-based techniques (such as the aforementioned 'deferred lighting' and so on), so if you're serious about supporting multiple dynamic lights, you might want to start looking into the programmable pipeline.

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most games only deal with one light at a time
eg quake3

draw object
for all lights
{
is object inside a spotlight?
yes - enable spotlight, enable blending
draw object again
}

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Quote:
most games only deal with one light at a time
eg quake3

draw object
for all lights
{
is object inside a spotlight?
yes - enable spotlight, enable blending
draw object again
}
Are you sure that's what Q3 does? IINM, dynamic entities such as characters and items are lit at the vertex level using a pre-computed 'light grid', while static geometry is lit using either pre-computed lightmaps or pre-computed vertex lighting.

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Quote:
Original post by jyk
Quote:
most games only deal with one light at a time
eg quake3

draw object
for all lights
{
is object inside a spotlight?
yes - enable spotlight, enable blending
draw object again
}
Are you sure that's what Q3 does? IINM, dynamic entities such as characters and items are lit at the vertex level using a pre-computed 'light grid', while static geometry is lit using either pre-computed lightmaps or pre-computed vertex lighting.


As you said, that's what Quake 3 does.
For Doom 3, which is shader based, it handles 1 light at a time I believe with additive blending (glBlendFunc(GL_ONE, GL_ONE))

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