3dsmax Light Decay (distance attenuation)

	inline float Decay(float att,float dist, float r0) {
	float s;
	if (decayType==DECAY_NONE || dist==0.0f) return att;
	if ((s=r0/dist)>=1.0f) return att;
	return (decayType==DECAY_INVSQ)? s*s*att: s*att;
	}
	float BaseObjLight::ApplyDistanceAtten( float dist )
	{
	float atten = 1.0f;
	if(ls.useNearAtten) {
	if(dist<ls.nearAttenStart) // Beyond range
	return 0;
	if(dist<ls.nearAttenEnd) {
	// in attenuated range
	float u = (dist - ls.nearAttenStart)/(ls.nearAttenEnd-ls.nearAttenStart);
	atten = u*u*(3-2*u); /* smooth cubic curve */
	}
	}
	if (ls.useAtten) {
	if(dist>ls.attenEnd) /* Beyond range */
	return 0;
	if(dist>ls.attenStart) {
	/* Outside full-intensity range */
	float u = (ls.attenEnd-dist)/(ls.attenEnd-ls.attenStart);
	atten *= u*u*(3-2*u); /* smooth cubic curve */
	}
	}
	// atten = Decay(atten,dist,ls.nearAttenEnd); // old way, changed by dan
	atten = Decay(atten,dist, decayRadius);
	return atten;
	}

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