3ds max lights decay

gistfile1.cpp

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;
}