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Speed up GlobalLightingPaletteEffect.

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Perform everything in integer arithmetic using some bit twiddling to avoid the performance cost of converting to and from floating point values.
This commit is contained in:
RoosterDragon
2015-12-31 06:26:05 +00:00
parent f7c6938e27
commit 208b51feb1
1 changed files with 36 additions and 5 deletions
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41
OpenRA.Mods.Common/Traits/PaletteEffects/GlobalLightingPaletteEffect.cs
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@@ -9,7 +9,6 @@
#endregion #endregion
using System.Collections.Generic; using System.Collections.Generic;
using System.Drawing;
using System.Linq; using System.Linq;
using OpenRA.Graphics; using OpenRA.Graphics;
using OpenRA.Traits; using OpenRA.Traits;
@@ -54,6 +53,12 @@ namespace OpenRA.Mods.Common.Traits
public void AdjustPalette(IReadOnlyDictionary<string, MutablePalette> palettes) public void AdjustPalette(IReadOnlyDictionary<string, MutablePalette> palettes)
{ {
// Calculate ambient color multipliers as integers for speed. To handle fractional ambiance, we'll increase
// the magnitude of the result by 8 bits.
var ar = (uint)((1 << 8) * Ambient * Red);
var ag = (uint)((1 << 8) * Ambient * Green);
var ab = (uint)((1 << 8) * Ambient * Blue);
foreach (var kvp in palettes) foreach (var kvp in palettes)
{ {
if (info.ExcludePalettes.Contains(kvp.Key)) if (info.ExcludePalettes.Contains(kvp.Key))
@@ -66,11 +71,37 @@ namespace OpenRA.Mods.Common.Traits
for (var x = 0; x < Palette.Size; x++) for (var x = 0; x < Palette.Size; x++)
{ {
/* Here is the reference code for the operation we are performing.
var from = palette.GetColor(x); var from = palette.GetColor(x);
var red = (int)(from.R * Ambient * Red).Clamp(0, 255); var r = (int)(from.R * Ambient * Red).Clamp(0, 255);
var green = (int)(from.G * Ambient * Green).Clamp(0, 255); var g = (int)(from.G * Ambient * Green).Clamp(0, 255);
var blue = (int)(from.B * Ambient * Blue).Clamp(0, 255); var b = (int)(from.B * Ambient * Blue).Clamp(0, 255);
palette.SetColor(x, Color.FromArgb(from.A, red, green, blue)); palette.SetColor(x, Color.FromArgb(from.A, r, g, b));
*/
// PERF: Use integer arithmetic to avoid costly conversions to and from floating point values.
var from = palette[x];
// 1: Extract each color component and shift it to the lower bits, then multiply with ambiance.
// 2: Because the ambiance was increased by 8 bits, our result has been shifted 8 bits up.
// If the multiply overflowed we clamp the value, otherwise we mask out the fractional bits.
// 3: Finally, we shift the color component back to its correct place. We're already 8 bits higher
// than expected due to the multiply, so we don't have to shift as far to get back.
var r1 = ((from & 0x00FF0000) >> 16) * ar;
var r2 = r1 >= 0x0000FF00 ? 0x0000FF00 : r1 & 0x0000FF00;
var r3 = r2 << 8;
var g1 = ((from & 0x0000FF00) >> 8) * ag;
var g2 = g1 >= 0x0000FF00 ? 0x0000FF00 : g1 & 0x0000FF00;
var g3 = g2 << 0;
var b1 = ((from & 0x000000FF) >> 0) * ab;
var b2 = b1 >= 0x0000FF00 ? 0x0000FF00 : b1 & 0x0000FF00;
var b3 = b2 >> 8;
// Combine all the adjusted components back together.
var a = from & 0xFF000000;
palette[x] = a | r3 | g3 | b3;
} }
} }
} }