I want an entity to glow when for example hit by something. The routine I am trying to use is:

MATERIAL* glow_on =
{
emissive_blue = 100;
emissive_green = 100;
emissive_red = 255;
power = 255;
}
MATERIAL* glow_off =
{
emissive_blue = 0;
emissive_green = 0;
emissive_red = 0;
power = 0;
}

function main()
{
...
entity.material=glow_on;
...
}

However nothing happens to the entity, it just stays the same. Can someone tell me how to make an entity glow.