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fix: smooth tail via separate line segment, body path stays grid-snapped

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Tail is now drawn as a separate DrawLine from interpolated tail position
to the grid-snapped second-to-last segment. Body path (segment[N-2]→head)
stays grid-snapped, preserving sharp corners while tail glides smoothly.
This commit is contained in:
Heller
2026-06-19 10:18:26 +00:00
parent 4446bd778f
commit d83234c8be
1 changed files with 71 additions and 48 deletions
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119
Snake.Avalonia/Views/SnakeRenderer.cs
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@@ -133,53 +133,37 @@ public sealed class SnakeRenderer : Control
var t = InterpolationT;
var segmentsList = Segments;
var prevList = PreviousSegments;
var count = segmentsList.Count;
// Build path for body (all segments except head)
var bodyGeometry = new StreamGeometry();
using (var ctx = bodyGeometry.Open())
// === 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.
if (count >= 2)
{
for (var i = segmentsList.Count - 1; i >= 1; i--)
var bodyGeometry = new StreamGeometry();
using (var ctx = bodyGeometry.Open())
{
var current = segmentsList[i];
var (vx, vy) = GetVisualPosition(current, i, t);
// 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);
ctx.BeginFigure(new Point(startX, startY), false);
if (i == segmentsList.Count - 1 && segmentsList.Count > 2)
// Draw through middle segments down to head
for (var i = count - 3; i >= 0; i--)
{
ctx.BeginFigure(new Point(vx, vy), false);
}
else if (i == segmentsList.Count - 1)
{
ctx.BeginFigure(new Point(vx, vy), false);
}
// Draw line segment
if (i > 1)
{
var (px, py) = GetVisualPosition(segmentsList[i - 1], i - 1, t);
var (px, py) = GetVisualPosition(segmentsList[i], i, t);
ctx.LineTo(new Point(px, py));
}
}
if (segmentsList.Count >= 2)
{
var (hx, hy) = GetVisualPosition(segmentsList[0], 0, t);
ctx.LineTo(new Point(hx, hy));
}
}
// Body thickness
var maxThickness = CellSize * 0.7;
var bodyThickness = Math.Max(CellSize * 0.35, maxThickness * 0.85);
var bodyPen = new Pen(SnakeBodyBrush, bodyThickness,
lineCap: PenLineCap.Round, lineJoin: PenLineJoin.Round);
context.DrawGeometry(null, bodyPen, bodyGeometry);
// Calculate body thickness based on segment position (tail thinner)
var maxThickness = CellSize * 0.7;
var minThickness = CellSize * 0.35;
// Draw body as a thick stroke
var bodyThickness = Math.Max(minThickness, maxThickness * 0.85);
var bodyPen = new Pen(SnakeBodyBrush, bodyThickness, lineCap: PenLineCap.Round, lineJoin: PenLineJoin.Round);
context.DrawGeometry(null, bodyPen, bodyGeometry);
// Draw a slightly thinner inner stroke for gradient effect
if (segmentsList.Count >= 2)
{
// Inner highlight stroke
var innerPen = new Pen(
new SolidColorBrush(SnakeHeadBrush.Color, 0.4),
bodyThickness * 0.5,
@@ -188,6 +172,32 @@ public sealed class SnakeRenderer : Control
context.DrawGeometry(null, innerPen, bodyGeometry);
}
// === Tail: separate fading line from interpolated tail to body ===
if (count >= 2)
{
var (tailX, tailY) = GetVisualPosition(segmentsList[count - 1], count - 1, t);
var (bodyEndX, bodyEndY) = GetVisualPosition(segmentsList[count - 2], count - 2, t);
// 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));
// Soft fading ellipse at the interpolated tail tip
var fadeRadius = tailThickness * 0.8;
context.DrawEllipse(
new SolidColorBrush(SnakeTailBrush.Color, 0.3),
null,
new Point(tailX, tailY),
fadeRadius, fadeRadius);
}
// Draw head
DrawHead(context, t);
@@ -373,18 +383,31 @@ public sealed class SnakeRenderer : Control
private (double X, double Y) GetVisualPosition(Position pos, int segmentIndex, double t)
{
// Only interpolate the head — all other segments stay grid-snapped
// to preserve sharp corners when the snake bends.
// Interpolating the tail creates diagonal shortcuts at corners because
// the tail position drifts while the adjacent segment is already at its
// new grid position.
if (segmentIndex != 0)
return (pos.X * CellSize + CellSize * 0.5, pos.Y * CellSize + CellSize * 0.5);
// Head (index 0): interpolated with easing for smooth movement
if (segmentIndex == 0)
{
var from = PreviousSegments != null && PreviousSegments.Count > 0
? AnimationHelper.GetPreviousPosition(0, Segments!, PreviousSegments, SnakeDirection)
: pos;
var from = PreviousSegments != null && PreviousSegments.Count > 0
? AnimationHelper.GetPreviousPosition(0, Segments!, PreviousSegments, SnakeDirection)
: pos;
return AnimationHelper.InterpolatePosition(from, pos, t, CellSize, useEasing: true);
}
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
return (pos.X * CellSize + CellSize * 0.5, pos.Y * CellSize + CellSize * 0.5);
}
}