Constant/linear/quadratic - No effect

...Never make adjustments to any light entity that high, some of the values for example are only valid from 0-10.
The adjustments you've been making would have changed the way your light edges appear, you can for example make the ring at the edge of your light very sharp rather than blended.
The brightness is what you want to adjust, where a normal light entity gives off the approximate amount of light from a typical source values are most commonly between 60-120, with 200 being bright and 600 a blinding light.

SDK Nuts

A fair amount. I chuckle.

Modifying the brightness has a much more powerful (and in this case, desirable) effect than the QLC modifiers.

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From reading the VRAD source, the Q, L & C values are normalized before the light's effect is computed. Therefore, only their relative values matter.

(In utils/vrad/lightmap.cpp:

float ratio = (dl->light.constant_attn + 100 * dl->light.linear_attn + 100 * 100 * dl->light.quadratic_attn);

if (ratio > 0)
{
VectorScale( dl->light.intensity, ratio, l->light.intensity);
}
}

The attenuation coefficient is calculated at 100 units distance from the light, then the light intensity is reduced so that the attenuation is exactly 1 at 100 units.)

So setting Q=1000, L=200, C=5 produces exactly the same lighting effect as Q=1, L=0.2, C=0.005. To make the light brighter, you must use the brightness setting, which is a linear multiplier. Changing Q, L & C only effect the shape of the light fall-off with distance; the normalization above ensures that their values do not effect the overall brightness.

Also, since only relative values matter, if you have two of the constants set to zero (e.g. L=0, C=0) it doesn't matter if you set Q=1, Q=500, Q=70000000 or Q=0.00000001, it will have absolutely no effect on the way the light works.

-----
VMEX & Pakrat:
http://www.geocities.com/cofrdrbob/

Message last edited by Rof on Dec 23rd 2005 at 16:01.

Rof:

I thought about this scenario, as I seemed to get slightly different results when C and L were 5000-1000 and Q was 10000, more so than with zero for the first two and very high for Q. Thank you very much for enlightening us.

**EDIT**

Forgot about this: the beta SDK includes new tags for light entities called "50 percent falloff distance" and "0 percent falloff distance"

The first is the distance where the light should fall to 50% of its set brightness, and the second is the distance at which the light should become almost non-existant. These two override linear, constant, and quadratic.

Message last edited by active.exe on Dec 23rd 2005 at 17:37.

I made a gallery of lights with different QLC settings.

The difference was akin to comparing sounds with volumes varying by fractions of decibels.

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Demented, sorry if I'm blind but where is this gallery?

_____________________________________
Feel free to take a look at my Snarkpit profile :
http://www.snarkpit.net/users.php?name=reaper47

It's one of my personal test maps. I don't have it hosted anywhere.

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It was mainly a failed test, since I couldn't see the difference between a quadratic light and a linear light with any certainty.

As far as I know, the only use of the QLC values by valve was setting the constant to 500,000 for the Combine spotlights. Otherwise, it was always 1,0,0. Maybe they'll be more important for HDR.

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Message last edited by Demented on Dec 25th 2005 at 21:57.

It's not an exclusively HDR thing. It's just that they don't seem to be exceptionally useful for everyday purposes. Since HDR has such a wider range of light values, manipulating the QLC and brightness values could be far more useful for controlling tonemapping limits and what-not.

In LDR circumstances, I know Valve normally uses 1,0,0 for everything.
Combine spotlights are 1,0,500000, so they make a kind of very-long-range one-color light.

Maybe if someone would make a gallery showing a few special effects the QLC values can be used to make, it would be worth hosting.

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