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d3dlight attenuation

Started by tomek_zielinski Jul 9, 2004 at 1:11 PM 4 replies 900+ views

Original Post

Jul 9, 2004 at 1:11 PM

Hey! I've got a quiestion about attenution - I understand basics but I couldn't get proper results... I want my light to be at full brightness in its position and totally black at D3DLIGHT8::Range, and to attenuate like x^2. So, are these proper settings: Attenuation0 = 0 Attenuation1 = 0 Attenuation2 = 1.0 no matter of what value Range is? thx in advance

tomek_zielinski

Jul 9, 2004 at 1:59 PM

[smile]

RenderTarget

Jul 9, 2004 at 4:42 PM

You won't be able to specify a smooth transition from 0 to 1 over 1/d^2, but you can get close. The range is just the cutoff distance, but 1/d^2 will never actually hit zero. By playing with att2, you can approach the range, but it's a matter of tweaking values that make things look right.

tomek_zielinski

Jul 9, 2004 at 5:12 PM

thanx, so it isn't possible to calculate exact attenuation factors?

RenderTarget

Jul 9, 2004 at 5:49 PM

Well, yeah, do the math:

1 / (att0 + att1 * d + att2 * d² )

What values of att0, att1, and att2 will bring that to zero? Only 0's for all of them, which of course would just turn the light off. For any other values (all of which have to be positive or zero), you'll never fall off to exactly zero. You can get close enough to look good, depending on the values and the range.

tomek_zielinski

Jul 9, 2004 at 6:06 PM

I've got lightmapped static world and dynamic character. And I want these characters to be lit comparably to objects in the world. Lightmapping uses quadratic attenuation:

(light_range^2 - dist_from_light_to-lumel^2)/(light_range^2)

and I would like to achieve similar effect with D3D lighting...

anyway, thx for the reply!

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