ray_trace_postgres.sql

ray_trace_postgres.sql

-- ported to postgres from https://observablehq.com/@pallada-92/sql-3d-engine
WITH RECURSIVE numbers AS (
  SELECT 0 AS n UNION ALL SELECT n+1 FROM numbers WHERE n<89
),
pixels AS (
  SELECT rows.n as row, cols.n as col
  FROM numbers as rows CROSS JOIN numbers as cols
  WHERE rows.n > 2 AND rows.n < 40 AND cols.n > -1 AND cols.n < 89
), rawRays AS (
  SELECT
    row, col,
    -0.9105 + col * 0.0065 + row * 0.0057 as x,
    -0.1315 + row * -0.0171 as y,
    0.6794 + col * 0.0045 + row * -0.0081 as z
  FROM pixels
), normsSq AS (
  SELECT row, col, x, y, z, x * x + y * y + z * z AS n2 FROM rawRays
), norms AS (
  SELECT row, col, x, y, z, (1 + n2) / 2.0 as n FROM normsSq
), rays AS (
  SELECT row, col, x / n AS x, y / n AS y, z / n AS z FROM norms
), iters AS (
  SELECT row, col, 0 as it, 0.0 as v FROM rays
  UNION ALL
  SELECT rays.row, rays.col, it + 1 AS it,
    v + GREATEST(ABS(0.75+v*x) - 0.3, ABS(0.75+v*y) - 0.3, ABS(-1.06+v*z) - 0.3, -(0.28 + ((0.75+v*x) * (0.75+v*x) + (0.75+v*y) * (0.75+v*y) + (-1.06+v*z) * (-1.06+v*z)) / 0.28) / 2.0 + 0.42) AS v
  FROM iters JOIN rays ON rays.row = iters.row AND rays.col = iters.col
  WHERE it < 15
), lastIters AS (
  SELECT it0.row, it0.col, it0.v AS v0, it1.v AS v1, it2.v AS v2
  FROM iters as it0
    JOIN iters AS it1 ON it0.row = it1.row AND it0.col = it1.col
    JOIN iters AS it2 ON it0.row = it2.row AND it0.col = it2.col
  WHERE it0.it = 15 AND it1.it = 14 AND it2.it = 13
), res AS (
  SELECT col, (v0 - v1) / (v1 - v2) as v FROM lastIters
)
SELECT string_agg(
  substring('$@B%8&WM#*oahkbdpqwmZO0QLCJUYXzcvunxrjft/|()1{}[]?-_+~<>i!lI;:,"^. '::text, CAST (round(1 + GREATEST(0, LEAST(66, v * 67))) AS INTEGER), 1)
  || CASE WHEN col = 88 THEN X'0A' ELSE '' END
, '')
FROM res;

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