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spots effect accuracy improvements #5341

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spots effect accuracy improvements #5341

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8a03b27
spots effect improvements
softhack007 Feb 2, 2026
e2bee4f
fixpoint scaling bugfix
softhack007 Feb 2, 2026
d643cef
Merge branch 'main' into spots_improvement
softhack007 Apr 8, 2026
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21 changes: 13 additions & 8 deletions wled00/FX.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2914,20 +2914,25 @@ static void spots_base(uint16_t threshold)
if (SEGLEN <= 1) FX_FALLBACK_STATIC;
if (!SEGMENT.check2) SEGMENT.fill(SEGCOLOR(1));

unsigned maxZones = SEGLEN >> 2;
unsigned zones = 1 + ((SEGMENT.intensity * maxZones) >> 8);
unsigned zoneLen = SEGLEN / zones;
unsigned offset = (SEGLEN - zones * zoneLen) >> 1;
// constants for fixed point scaling
constexpr uint8_t ZONELEN_FP_SHIFT = 3;
constexpr uint32_t ZONELEN_FP_SCALE = 1U << ZONELEN_FP_SHIFT;

unsigned maxZones = max(1U, SEGLEN >> 2); // prevents "0 zones"
unsigned zones = 1U + ((uint32_t(SEGMENT.intensity) * maxZones) >> 8);
unsigned zoneLen = SEGLEN / zones;
unsigned zoneLen8 = (SEGLEN * ZONELEN_FP_SCALE) / zones; // zoneLength * 8 (fixed‑point) -> avoids gaps at right/left sides
unsigned offset = (SEGLEN - ((zones * zoneLen8) >> ZONELEN_FP_SHIFT)) >> 1;

for (unsigned z = 0; z < zones; z++)
{
unsigned pos = offset + z * zoneLen;
unsigned pos = offset + ((z * zoneLen8) >> ZONELEN_FP_SHIFT);
for (unsigned i = 0; i < zoneLen; i++)
{
unsigned wave = triwave16((i * 0xFFFF) / zoneLen);
if (wave > threshold) {
unsigned index = 0 + pos + i;
unsigned s = (wave - threshold)*255 / (0xFFFF - threshold);
unsigned index = pos + i;
unsigned s = ((wave - threshold)*255 / (0xFFFF - threshold)) & 0xFF; // & 0xFF prevents overflow in next line
Comment on lines +2921 to +2935
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@coderabbitai coderabbitai Bot Apr 8, 2026

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⚠️ Potential issue | 🟠 Major

Use boundary-derived widths to keep the spots evenly spaced.

Line 2923 still fixes every zone to SEGLEN / zones, while Line 2929 places starts on fractional boundaries. On lengths that do not divide evenly, the leftover pixels turn into visible holes instead of evenly spaced spots. Derive each zone width from the next boundary instead of reusing the truncated integer width.

♻️ Proposed fix 
-  unsigned zoneLen  = SEGLEN / zones;
-  unsigned zoneLen8 = (SEGLEN * ZONELEN_FP_SCALE) / zones; // zoneLength * 8 (fixed‑point) -> avoids gaps at right/left sides
-  unsigned offset   = (SEGLEN - ((zones * zoneLen8) >> ZONELEN_FP_SHIFT)) >> 1;
+  unsigned zoneLen8 = (uint32_t(SEGLEN) * ZONELEN_FP_SCALE) / zones; // zoneLength * 8 (fixed-point) -> avoids gaps at right/left sides
+  unsigned offset   = (SEGLEN - ((uint32_t(zones) * zoneLen8) >> ZONELEN_FP_SHIFT)) >> 1;

   for (unsigned z = 0; z < zones; z++)
   {
-    unsigned pos = offset + ((z * zoneLen8) >> ZONELEN_FP_SHIFT);
+    unsigned pos = offset + ((uint32_t(z) * zoneLen8) >> ZONELEN_FP_SHIFT);
+    unsigned nextPos = (z + 1 == zones)
+      ? (SEGLEN - offset)
+      : offset + ((uint32_t(z + 1) * zoneLen8) >> ZONELEN_FP_SHIFT);
+    unsigned zoneLen = nextPos - pos;
     for (unsigned i = 0; i < zoneLen; i++)
🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@wled00/FX.cpp` around lines 2921 - 2935, The loop currently computes a
uniform zoneLen (SEGLEN / zones) but computes per-zone start positions using
fractional boundaries (offset + ((z * zoneLen8) >> ZONELEN_FP_SHIFT)), causing
leftover pixels to become gaps; change the inner loop to derive each zone's
width from the next fractional boundary instead of reusing zoneLen: compute pos
for zone z using the existing fractional formula (pos = offset + ((z * zoneLen8)
>> ZONELEN_FP_SHIFT)) and posNext for z+1 similarly, then set the per-zone width
as zoneWidth = posNext - pos (for the last zone use SEGLEN - pos), and iterate i
from 0 to zoneWidth so spots fill evenly; update uses of zoneLen and any
dependent indexing (variables: zones, zoneLen, zoneLen8, offset, pos)
accordingly.

SEGMENT.setPixelColor(index, color_blend(SEGMENT.color_from_palette(index, true, PALETTE_SOLID_WRAP, 0), SEGCOLOR(1), uint8_t(255-s)));
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}
}
Expand All @@ -2951,7 +2956,7 @@ void mode_spots_fade()
unsigned tr = (t >> 1) + (t >> 2);
spots_base(tr);
}
static const char _data_FX_MODE_SPOTS_FADE[] PROGMEM = "Spots Fade@Spread,Width,,,,,Overlay;!,!;!";
static const char _data_FX_MODE_SPOTS_FADE[] PROGMEM = "Spots Fade@Speed,Width,,,,,Overlay;!,!;!";
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@DedeHai DedeHai Feb 3, 2026

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while you are at it: rename "Width" to "Density" for both variants?


//each needs 12 bytes
typedef struct Ball {
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