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fix: tail as full body segment + fading ghost for smooth illusion

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Tail is now part of the main body path (grid-snapped, full thickness,
sharp corners). Smooth movement illusion via fading ghost circle at
the old tail position that fades out during the tick.
This commit is contained in:
Heller
2026-06-19 10:22:33 +00:00
parent d83234c8be
commit 36bfe5ad45
1 changed files with 25 additions and 43 deletions
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64
Snake.Avalonia/Views/SnakeRenderer.cs
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@@ -135,21 +135,21 @@ public sealed class SnakeRenderer : Control
var segmentsList = Segments;
var count = segmentsList.Count;
// === Body path: from segment[Count-2] down to segment[0] ===
// Build with grid-snapped middle segments → sharp corners.
// The tail (segment[Count-1]) is excluded and drawn separately below.
// === Body path: from segment[Count-1] (tail) through segment[0] (head) ===
// All segments use GetVisualPosition — middle/body returns grid-snapped,
// head returns interpolated. Tail is grid-snapped, giving sharp corners
// with full body thickness.
if (count >= 2)
{
var bodyGeometry = new StreamGeometry();
using (var ctx = bodyGeometry.Open())
{
// Start at second-to-last segment (grid-snapped for count>2,
// head-interpolated for count==2 — harmless since it's just the head)
var (startX, startY) = GetVisualPosition(segmentsList[count - 2], count - 2, t);
// Start at tail (last segment, grid-snapped)
var (startX, startY) = GetVisualPosition(segmentsList[count - 1], count - 1, t);
ctx.BeginFigure(new Point(startX, startY), false);
// Draw through middle segments down to head
for (var i = count - 3; i >= 0; i--)
for (var i = count - 2; i >= 0; i--)
{
var (px, py) = GetVisualPosition(segmentsList[i], i, t);
ctx.LineTo(new Point(px, py));
@@ -172,30 +172,26 @@ public sealed class SnakeRenderer : Control
context.DrawGeometry(null, innerPen, bodyGeometry);
}
// === Tail: separate fading line from interpolated tail to body ===
if (count >= 2)
// === Fading ghost circle at old tail position ===
// Creates the illusion of smooth tail movement without affecting
// the body path geometry (which stays grid-snapped with sharp corners).
if (count >= 2 && PreviousSegments != null && PreviousSegments.Count > 0)
{
var (tailX, tailY) = GetVisualPosition(segmentsList[count - 1], count - 1, t);
var (bodyEndX, bodyEndY) = GetVisualPosition(segmentsList[count - 2], count - 2, t);
var opacity = 0.4 * (1.0 - t);
if (opacity > 0)
{
var oldTailPos = PreviousSegments[PreviousSegments.Count - 1];
var currentTailPos = segmentsList[count - 1];
// Fading tail line — thinner and semi-transparent
var tailThickness = CellSize * 0.35;
var tailPen = new Pen(
new SolidColorBrush(SnakeTailBrush.Color, 0.5),
tailThickness,
lineCap: PenLineCap.Round,
lineJoin: PenLineJoin.Round);
context.DrawLine(tailPen,
new Point(tailX, tailY),
new Point(bodyEndX, bodyEndY));
var (ghostX, ghostY) = AnimationHelper.InterpolatePosition(
oldTailPos, currentTailPos, t, CellSize, useEasing: false);
// Soft fading ellipse at the interpolated tail tip
var fadeRadius = tailThickness * 0.8;
context.DrawEllipse(
new SolidColorBrush(SnakeTailBrush.Color, 0.3),
new SolidColorBrush(SnakeBodyBrush.Color, opacity),
null,
new Point(tailX, tailY),
fadeRadius, fadeRadius);
new Point(ghostX, ghostY),
CellSize * 0.35, CellSize * 0.35);
}
}
// Draw head
@@ -393,21 +389,7 @@ public sealed class SnakeRenderer : Control
return AnimationHelper.InterpolatePosition(from, pos, t, CellSize, useEasing: true);
}
// Tail (last segment, only when there are multiple segments): interpolated LINEARLY
// This is used ONLY in the separate tail-drawing code, not in the main body path,
// so it does NOT create diagonal shortcuts at corners.
// The tail line connects from this interpolated position to the grid-snapped
// second-to-last segment.
if (Segments != null && Segments.Count > 1 && segmentIndex == Segments.Count - 1)
{
var from = PreviousSegments != null && PreviousSegments.Count > 0
? AnimationHelper.GetPreviousPosition(segmentIndex, Segments!, PreviousSegments, SnakeDirection)
: pos;
return AnimationHelper.InterpolatePosition(from, pos, t, CellSize, useEasing: false);
}
// Middle segments: grid-snapped for sharp corners
// All other segments (body and tail): grid-snapped for sharp corners
return (pos.X * CellSize + CellSize * 0.5, pos.Y * CellSize + CellSize * 0.5);
}
}