GoKawiilRayTracer — a ray tracer in ClickHouse SQL
A path tracer written entirely as ClickHouse SQL queries, rendering straight to a PNG via ClickHouse's PNG output format. No UDFs and no external code — a single SELECT computes every pixel.
It renders the word ClickHouse as glassy, chrome lettering — in the spirit of Andrew Kensler's famous Pixar business-card ray tracer — and, in the scene above, sets it floating over a procedurally generated landscape, reflecting the terrain and casting shadows on the hills.
See also:
How it works
The whole renderer lives in one query:
Pixels are rows. numbers_mt(width * height * samples) produces one row per (pixel, sample) ; samples are averaged with GROUP BY pixel , and the output columns r, g, b (in [0, 1] ) plus explicit x, y coordinate columns ( pixel % width , intDiv(pixel, width) ) are written to the PNG output format. The explicit coordinates let the writer place each pixel by its position, so the rows need no ORDER BY and the heavy per-pixel work stays parallel across all cores.
produces one row per ; samples are averaged with , and the output columns (in ) plus explicit coordinate columns ( , ) are written to the output format. The explicit coordinates let the writer place each pixel by its position, so the rows need no and the heavy per-pixel work stays parallel across all cores. 3D math on tuples. Vectors are Tuple(Float64, Float64, Float64) ; dotProduct , L2Normalize , tuplePlus , tupleMultiplyByNumber , … do the linear algebra, wrapped in short lambda aliases ( va , vs , vm , vd , vn , vc , vref ).
Vectors are ; , , , , … do the linear algebra, wrapped in short lambda aliases ( , , , , , , ). The bounce loop is arrayFold . Every ray is advanced exactly one mirror bounce per fold step over range(maxDepth) — a loop inside each row, so rows stay independent and the render parallelizes across all CPU cores. (The first version used a WITH RECURSIVE CTE instead — see the queries below.)
Every ray is advanced exactly one mirror bounce per fold step over — a loop inside each row, so rows stay independent and the render parallelizes across all CPU cores. (The first version used a CTE instead — see the queries below.) let -bindings via arrayMap . ClickHouse WITH lambdas are call-by-name, so passing a value as a parameter re-expands the expression and blows up the query tree. Intermediates are therefore bound by value with arrayMap(x -> body, [expr])[1] , a one-element-array "let".
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