Many performers can, with a word or gesture, make you laugh, or cry, or squirm. Rare is the virtuoso who can harness two. Robin Williams? He was capable of all three. Film to film or show to show, he could be hilarious, or heartbreaking, or utterly terrifying.

It is tempting to focus most of all on the laughter today - perhaps because recalling riffs, impersonations and pratfalls helps offset the tragedy of his too-soon death; or perhaps because making us laugh in our living rooms made him feel like more than a movie star. He felt like a friend. Sometimes a warm, gentle one, sometimes a rowdy one, but always welcome. And yet like many great comics, he was also a fine, often daring, dramatic talent, open to unsettling and challenging his audience. It is as if there has been a different Robin Williams waiting for us at every stage of our voyage.

My memories of Robin Williams centre foremost on childhood. Through films like Jumanji, Mrs Doubtfire, Flubber and Hook he was a constant presence, and companion. Though not all of the films hold up, there could have been no more perfect benevolent mad scientist or overgrown Peter Pan - Williams' infectious energy always suggested a boy who refused to ever really grow up. He never stopped headlining family films, although their quality wavered - the committed mania that enlivened his best work was also capable of tipping from endearing into exhausting, just as the films have sometimes lurched from sweetness into the unbearably saccharine. Yet our affection remains, undimmed, for the biggest kid in the room.

Improbably, the Genie in Aladdin may just be the quintessential Robin Williams comedy role. The wildly charismatic performance enlivens, but never quite overpowers, the film and embraces rather than constricts his talent for improvisation and impersonation. It is as if Williams needed to be recreated in pen and pencil to do justice to his elasticity of expression, imagination and speed. He was so good (and so undeniably 'Robin Williams') that he single-handedly ushered in the era of celebrity voice-casting. Disney knew they were onto a good thing - the studio reneged on their agreement that Williams' name and image not be used for marketing the film, and that the Genie's placement in the advertising campaign be limited. The betrayal stung (Williams did the film for little money because he felt his children would enjoy it), but the temptation to fling the Genie onto every billboard in America must have been irresistible. It was not his last voice role (FernGully and Happy Feet, amongst others, have followed), but it remains his best.

Williams' second career in drama was often as successful as his first. He exposed a weariness beneath that wild smile in Dead Poet's Society and Good Will Hunting; it seemed perfectly natural for him to immediately leap from extended childhood to symbolic fatherhood, guiding a new generation of lost boys towards their better selves. The playtime companion became the greatest teacher we ever had; the life coach to nudge us into adulthood; the father who never forgot the power of play.

That is why it was so startling to see his capacity to tap into real darkness. There was little of the clown in Williams' portrayal of the lonely, obsessive Sy Parrish in One Hour Photo - his familiar mania was left to simmer beneath the skin of a quiet soul, to curdle as we awaited explosion. As the villain in Christopher's Nolan's underrated Insomnia he could flash that familiar grin, and yet have drained it of all the treasured warmth.

The great roles have been rarer in recent years, but Williams never stopped being hilarious (Youtube his standup if in doubt) and challenging (World's Greatest Dad). My last glimpse of Robin Williams was his guest spot on Louie; a gorgeously black seven minutes that sees him accompany Louis CK to a strip club in memory of much-loathed dead acquaintance - only to find the strippers struck with genuine grief. After an appropriate spell of awkwardness, the duo depart in bewildered laughter, discovering how poor a grasp they had on the deceased, and part with a promise on their lips to attend one anothers' funerals.

The real Williams will have no shortage of mourners. It may be redundant to list the personal virtues of a man one only knows through stage and screen; suffice to say, few in the entertainment world are as highly respected or as widely loved. One wishes that could have been enough to keep him with us a little longer.

So here's another drop in the well of grief for a talent lost too soon, and, more importantly, a man who brought happiness not only to the lives of those he knew and loved, but millions more around the world, even if he could not, in the end, find enough for himself. I will go on replaying raucous old standup routines and Disney showtunes in memory of a great comedian; when I muster the courage, I'll slip One Hour Photo back in the DVD player in memory of a great actor. I may not resist the urge to stand on a desk and cry, "Oh Captain my Captain".

I'll end with my favourite scene from Good Will Hunting; on opening up, on grief, on loss, on love. For a few minutes, it is as if an old friend is still here to guide us.