You cause ammunition, including shuriken, to exude radiant energy. Creatures that take penalties in bright light take these penalties for 1 round after being struck by such ammunition. Undead and creatures harmed by sunlight take an additional 1d6 points of damage from such projectiles. This extra damage and half of any other damage you deal with an affected projectile results directly from radiant energy and is not subject to damage resistance.
Obviously, the extra damage only applies to undead and creatures harmed by sunlight. However, does the "ignores damage resistance" portion also apply only to such creatures, or would you be able to use it to punch through the DR of opponents unaffected by sunlight -- say, demons, or golems?
It is written as to only harm undead creatures and other creatures that are harmed by sunlight.
In short if the creature is not harmed by sunlight the extra 1d6 is never applied.