Decodes one texel of the surface-point attachment the renderer writes during
pickPoint: xyz hold the camera-relative f32 position, w is 1 where a
surface fragment survived depth and section tests and 0 (the clear value)
where only background was hit. The camera origin is added back in JavaScript
numbers so the result carries ADR-0005 precision, not f32 precision.
Decodes one texel of the surface-point attachment the renderer writes during
pickPoint: xyz hold the camera-relative f32 position, w is 1 where a surface fragment survived depth and section tests and 0 (the clear value) where only background was hit. The camera origin is added back in JavaScript numbers so the result carries ADR-0005 precision, not f32 precision.