Run Over: POINTS Culls points based on given frame range
float startFrame = chf("startFrame");
float endFrame = chf("endFrame");
float cull = chramp("lifeRamp", fit(@Frame, startFrame, endFrame, 0, 1));
float pt = fit01(cull, 0, @numpt);
if(@ptnum < pt)
{
removepoint(0, @ptnum);
}