Halliday & Matthiessen (1999: 210):
Qualities of projection are all scalar and they are, as we just noted, agnate with processes of sensing in figures of sensing; they are often realised by participial verb forms used as adjectives. The thing they are assigned to, as Attribute or as Epithet, is agnate either with the Senser (the 'like' type, realised by v-en if verbal in origin: happy, sad, angry, afraid, frightened, certain, sure) or with the Phenomenon (the 'please' type, realised by v-ing if verbal in origin: sad(dening), tragic, irritating, scary, certain).
From this it follows that when they are agnate with the Senser, they are ascribed to conscious beings (as in an angry child/boss/cat), whereas when they are agnate with the Phenomenon, they can be ascribed not only to things but also to metathings, i.e. to projections (as in it's sad(dening)/tragic/irritating/scary/certain that they ignore world opinion). In the former case, these qualities may be 'transferred' to tokens of the senser's sensing, as in an angry face/look/letter/reaction.