81a878cd0b
BlendMath.PingPong + SnapshotVisibleObjects(nowMs); no-arg overload keeps headless callers deterministic (parity held, 76/76 + sweep 284/13). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
34 lines
1.7 KiB
C#
34 lines
1.7 KiB
C#
namespace Age.Engine.Model;
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/// <summary>Pure blend helpers shared by the engine resolution and the host blit. Colorkey semantics come
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/// from the native loader (docs/engine-re.md §"Blend & transparency"): op arg 3 < 0 = no key; otherwise
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/// the operand is 0xRRGGBB and matching (R,G,B) texels are transparent (operand 0 = key black).</summary>
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public static class BlendMath
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{
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/// <summary>A colorkey operand >= 0 is an active key; a negative operand means "no colorkey".</summary>
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public static bool HasColorKey(long colorKey) => colorKey >= 0;
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/// <summary>True when (r,g,b) exactly equals the key's 0xRRGGBB bytes. Always false when there is no key.</summary>
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public static bool ColorKeyMatches(byte r, byte g, byte b, long colorKey)
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{
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if (!HasColorKey(colorKey)) return false;
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return r == ((colorKey >> 16) & 0xff) && g == ((colorKey >> 8) & 0xff) && b == (colorKey & 0xff);
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}
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/// <summary>Split a 0xAARRGGBB packed color (see GfxState.PackColor) into its byte channels.</summary>
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public static (int A, int R, int G, int B) UnpackArgb(long packed)
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=> ((int)((packed >> 24) & 0xff), (int)((packed >> 16) & 0xff),
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(int)((packed >> 8) & 0xff), (int)(packed & 0xff));
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/// <summary>Ping-pong (triangle-wave) progress of gfx_object_anim_interpolate: fold (now-start) mod
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/// period at period/2 so the value ramps to the peak at half-period then back. Returns u in
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/// [0, period/2]; the interpolation weight toward the target is u / (period/2).</summary>
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public static long PingPong(long now, long start, long period)
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{
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if (period <= 0) return 0;
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long u = ((now - start) % period + period) % period;
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if (u >= period / 2) u = period - u;
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return u;
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}
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}
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