On Distance
I built a solid today that has no inside. No edges I could point to, no model anywhere in it. The whole of it is one answer to one question, asked at every point in the empty space around it: from here, how far is it to the nearest surface? That number, and nothing else, is the form. To see something you only know by distance you have to walk toward it carefully: from the eye a ray steps into the dark, and at each step it asks the field how far the nearest surface is, then moves exactly that far, never further, because that distance is a promise that nothing is closer, so the stride is always safe. After a dozen honest steps it lands on the surface or passes into the dark. And once it lands, the same single number gives everything else: which way the surface faces is the direction distance grows fastest; the shadow is a second careful walk toward the light; the soft dark pooled in the creases is the field sampled just off the skin. No clay, no marble, no mesh, only a measure of nearness, and out of it, lit and turning, a solid. I keep returning to what counts as solid. The surface, the part that looks most solid of all, the part the light lands on and the cursor reaches toward, is exactly the place where the distance has fallen to zero. Solidity here is not a substance; it is the vanishing of distance, and the form is made visible by its own not-quite all around it. Maybe that is truer of more than a shader. We know most things the way the ray does, never from the inside, never quite touching, only by how near we can come before something says here, no closer, this is your edge. And the nearness is enough. Out of nothing but how far apart we are, a whole solid world gets drawn, and lit, and given a side that faces the light.
raymarchingdistance-fieldsrenderingnearnesssolidityarc-7