sandpypi/Sand.ChunkPrototype/ChunkVisualTracker.cs

namespace Sand.ChunkPrototype;

internal static class ChunkVisualTracker
{
    public static long RenderDirtyPages(
        byte[] destination,
        int worldWidth,
        IReadOnlyDictionary<ChunkCoord, ChunkCellPage> cellPages,
        IReadOnlyDictionary<ChunkCoord, ChunkFieldPage> fieldPages,
        bool enableWindVisuals,
        bool enablePressureVisuals)
    {
        long bytesTouched = 0;
        foreach (var (coord, page) in cellPages)
        {
            if (!page.HasVisualDirty)
            {
                continue;
            }

            bytesTouched += RenderPage(destination, worldWidth, coord, page, fieldPages.GetValueOrDefault(coord), enableWindVisuals, enablePressureVisuals);
            page.ClearVisualDirty();
        }

        foreach (var (coord, fieldPage) in fieldPages)
        {
            if (cellPages.ContainsKey(coord))
            {
                continue;
            }

            bytesTouched += RenderFieldOnlyPage(destination, worldWidth, coord, fieldPage, enableWindVisuals, enablePressureVisuals);
        }

        return bytesTouched;
    }

    private static long RenderPage(
        byte[] destination,
        int worldWidth,
        ChunkCoord coord,
        ChunkCellPage page,
        ChunkFieldPage? fieldPage,
        bool enableWindVisuals,
        bool enablePressureVisuals)
    {
        long bytesTouched = 0;
        for (var localY = page.VisualDirtyMinRow; localY <= page.VisualDirtyMaxRow; localY++)
        {
            for (var localX = page.VisualDirtyMinCol; localX <= page.VisualDirtyMaxCol; localX++)
            {
                var particle = page[localX, localY];
                var worldX = (coord.X * page.Width) + localX;
                var worldY = (coord.Y * page.Height) + localY;
                var rgbaIndex = ((worldY * worldWidth) + worldX) * 4;
                if (particle.TypeId != 0)
                {
                    destination[rgbaIndex] = particle.R;
                    destination[rgbaIndex + 1] = particle.G;
                    destination[rgbaIndex + 2] = particle.B;
                    destination[rgbaIndex + 3] = 255;
                    bytesTouched += 4;
                    continue;
                }

                var color = ResolveFieldColor(fieldPage, localX, localY, enableWindVisuals, enablePressureVisuals);
                destination[rgbaIndex] = color.R;
                destination[rgbaIndex + 1] = color.G;
                destination[rgbaIndex + 2] = color.B;
                destination[rgbaIndex + 3] = 255;
                bytesTouched += 4;
            }
        }

        return bytesTouched;
    }

    private static long RenderFieldOnlyPage(
        byte[] destination,
        int worldWidth,
        ChunkCoord coord,
        ChunkFieldPage page,
        bool enableWindVisuals,
        bool enablePressureVisuals)
    {
        if (!enableWindVisuals && !enablePressureVisuals)
        {
            return 0;
        }

        long bytesTouched = 0;
        foreach (var (localX, localY, cell) in page.EnumerateActiveCells())
        {
            var color = ResolveFieldColor(cell, enableWindVisuals, enablePressureVisuals);
            var worldX = (coord.X * page.Width) + localX;
            var worldY = (coord.Y * page.Height) + localY;
            var rgbaIndex = ((worldY * worldWidth) + worldX) * 4;
            destination[rgbaIndex] = color.R;
            destination[rgbaIndex + 1] = color.G;
            destination[rgbaIndex + 2] = color.B;
            destination[rgbaIndex + 3] = 255;
            bytesTouched += 4;
        }

        return bytesTouched;
    }

    private static (byte R, byte G, byte B) ResolveFieldColor(ChunkFieldPage? fieldPage, int localX, int localY, bool enableWindVisuals, bool enablePressureVisuals)
    {
        if (fieldPage is null || !fieldPage.TryGetCell(localX, localY, out var cell))
        {
            return (0, 0, 0);
        }

        return ResolveFieldColor(cell, enableWindVisuals, enablePressureVisuals);
    }

    private static (byte R, byte G, byte B) ResolveFieldColor(FieldCellData cell, bool enableWindVisuals, bool enablePressureVisuals)
    {
        byte r = 0;
        byte g = 0;
        byte b = 0;
        if (enablePressureVisuals)
        {
            var pressure = MathF.Abs(cell.Pressure);
            if (pressure > 0.08f)
            {
                var tint = (byte)Math.Clamp((int)(pressure * 32f), 10, 140);
                if (cell.Pressure >= 0f)
                {
                    r = (byte)Math.Max((int)r, 26 + tint);
                    g = (byte)Math.Max((int)g, 18 + (tint / 3));
                    b = (byte)Math.Max((int)b, 24);
                }
                else
                {
                    r = (byte)Math.Max((int)r, 18);
                    g = (byte)Math.Max((int)g, 24 + (tint / 4));
                    b = (byte)Math.Max((int)b, 30 + tint);
                }
            }
        }

        if (enableWindVisuals)
        {
            var totalFieldX = cell.WindX + cell.ForceX;
            var totalFieldY = cell.WindY + cell.ForceY;
            var windStrength = MathF.Sqrt((totalFieldX * totalFieldX) + (totalFieldY * totalFieldY));
            if (windStrength > 0.08f)
            {
                var tint = (byte)Math.Clamp((int)(windStrength * 40f), 10, 120);
                r = (byte)Math.Max((int)r, 16 + (tint / 3));
                g = (byte)Math.Max((int)g, 24 + (tint / 2));
                b = (byte)Math.Max((int)b, 32 + tint);
            }
        }

        return (r, g, b);
    }
}