位置不是挑的
When every other place is ruled out, the last one decides everything.
投影機不是我們挑的位置。其他地方都不行，剩下這一個。
讓它動不難，難的是它能站在哪裡
把投影機藏進天花其實不難。升降機是現成的，電動幕也是現成的，買回來裝上去，就會降、就會收。難的從來不是讓它動，是它能站在哪裡。
位置一個一個被排掉
最理想的那個位置，上面壓著消防管線，讓不出深度。改從餐廳那側打過來，距離不夠、斜度太大，光會打到人的頭。位置一個一個被排掉，最後只剩一個，角度、高度、距離跟著被鎖死，沒有第二種擺法。
剩下的那一個，藏不住它
但那個位置藏不住它。要收進天花，就得裝一支升降機；升降機降得下來，收回來卻塞不回去，除非天花再往下降一截。這是一間挑高的房子，降不得。退這一步，前面算好的全部作廢。這一題，是我們在圖上自己撞上的。
投影機不動，讓天花打開
投影機不升降，固定在樑裡。前面是一片夾板做的弧形蓋子，跟著天花的弧，像相機快門一樣往上開。蓋子很長，拉一個點會扭，我們讓那一個點變成一整條。
蓋子開完，鏡頭才露得出來；布幕降到底，畫面才打得出去。三件事走完的時間不一樣，慢一步，畫面就打在蓋子上，或是切掉一半。這個時序，是試機的時候才發現的。天花，一公分都沒有降。
怎麼辦到的，這題我們留著。影片裡那張剖面不是畫來示意的，是這個案子的施工圖，投影機的位置、投射線、對面那面幕，都在原圖上量得到。最後三張完工照是同一個機位，從白天窗簾開著，到天花打開、畫面出來，再到窗簾拉上，中間沒有換過鏡頭。
「位置不是挑的，是被排剩下的。」
家裡有樑、有柱、有拆不掉的東西，想讓它變成好看的那一部分，跟我們談。
Hiding a projector in a ceiling is not hard; lifts and motorised screens are off the shelf. The hard part is where it can stand. The ideal position had sprinkler pipes above it. Projecting from the dining side meant too short a throw at too steep an angle, straight into people's heads. One by one the positions were ruled out until a single one remained, and that one could not hide it: a lift would come down but could not retract without lowering the ceiling, in a double-height house. So the projector does not move. It is fixed inside the beam, behind a long curved plywood cover that follows the ceiling and opens upward like a camera shutter. Pulled from one point, a cover that long would twist, so we turned that one point into a whole line. Cover, lens and screen each take a different time to travel; one step late and the image lands on the cover or is cut in half. We found that timing during commissioning. The ceiling was not lowered by a single centimetre.