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Current rotation fixes #81

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Current rotation fixes #81

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2c816f6
fix 1/2 movement/current-rotation, tilt broken due to misplaced paren
tolgraven Aug 9, 2019
97291c2
fix 2/2 movement/current-rotation, only mul rot by pi/2, else 180deg …
tolgraven Aug 9, 2019
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10 changes: 5 additions & 5 deletions src/afterglow/effects/movement.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -55,22 +55,22 @@
(chan-fx/apply-channel-value buffers c tilt))
(swap! (:movement *show*) #(assoc-in % [:current direction-key] [pan tilt]))))

(defn current-rotation
(defn current-rotation ;XXX just store the rotations instead - this will always be slower and sometimes solutions will vary...
"Given a head and DMX pan and tilt values, calculate a
transformation that represents the current orientation of the head
as compared to the default orientation of facing directly towards
the positive Z axis."
[head pan tilt]
(let [rotation (Transform3D. (:rotation head))]
(when-let [pan-scale (:pan-half-circle head)]
(let [dmx-pan (/ (- pan (:pan-center head)) pan-scale)
(let [pan-half-rotations (/ (- pan (:pan-center head)) pan-scale)
adjust (Transform3D.)]
(.rotY adjust (* Math/PI dmx-pan))
(.rotY adjust (* Math/PI 0.5 pan-half-rotations))
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Copilot AI Dec 20, 2025

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The multiplication by 0.5 appears to be incorrect. The variable pan-half-rotations already represents the number of half-circles (180-degree units), where one half-circle equals π radians. Therefore, the conversion to radians should be Math/PI * pan-half-rotations, not Math/PI * 0.5 * pan-half-rotations.

This can be verified by examining the inverse calculation in angle-to-dmx-value in transform.clj (line 229), which uses the formula: center-value + (angle / Math/PI) * half-circle-value. Rearranging this gives: angle = ((dmx - center) / half-circle-value) * Math/PI, which matches what the variable name suggests but contradicts the current implementation.

With the current code, a fixture will only rotate to half the intended angle.

Copilot uses AI. Check for mistakes.
(.mul rotation adjust)))
(when-let [tilt-scale (:tilt-half-circle head)]
(let [dmx-tilt (/ (- tilt (:tilt-center head) tilt-scale))
(let [tilt-half-rotations (/ (- tilt (:tilt-center head)) tilt-scale)
adjust (Transform3D.)]
(.rotX adjust (* Math/PI dmx-tilt))
(.rotX adjust (* Math/PI 0.5 tilt-half-rotations))
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Copilot AI Dec 20, 2025

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The multiplication by 0.5 appears to be incorrect. The variable tilt-half-rotations already represents the number of half-circles (180-degree units), where one half-circle equals π radians. Therefore, the conversion to radians should be Math/PI * tilt-half-rotations, not Math/PI * 0.5 * tilt-half-rotations.

This can be verified by examining the inverse calculation in angle-to-dmx-value in transform.clj (line 229), which uses the formula: center-value + (angle / Math/PI) * half-circle-value. Rearranging this gives: angle = ((dmx - center) / half-circle-value) * Math/PI, which matches what the variable name suggests but contradicts the current implementation.

With the current code, a fixture will only rotate to half the intended angle.

Copilot uses AI. Check for mistakes.
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@tolgraven tolgraven Dec 20, 2025

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hmm might have had some other thing that was causing end result angles to be off then... will investigate

(.mul rotation adjust)))
rotation))

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