FlameLashDrawer.cs

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using Microsoft.Xna.Framework;
using Terraria.Graphics.Shaders;
 
namespace Terraria.Graphics;
 
public struct FlameLashDrawer
{
    private static VertexStrip _vertexStrip = new VertexStrip();
 
    private float transitToDark;
 
    public void Draw(Projectile proj)
    {
        transitToDark = Utils.GetLerpValue(0f, 6f, proj.localAI[0], clamped: true);
        MiscShaderData miscShaderData = GameShaders.Misc["FlameLash"];
        miscShaderData.UseSaturation(-2f);
        miscShaderData.UseOpacity(MathHelper.Lerp(4f, 8f, transitToDark));
        miscShaderData.Apply();
        _vertexStrip.PrepareStripWithProceduralPadding(proj.oldPos, proj.oldRot, StripColors, StripWidth, -Main.screenPosition + proj.Size / 2f);
        _vertexStrip.DrawTrail();
        Main.pixelShader.CurrentTechnique.Passes[0].Apply();
    }
 
    private Color StripColors(float progressOnStrip)
    {
        float lerpValue = Utils.GetLerpValue(0f - 0.1f * transitToDark, 0.7f - 0.2f * transitToDark, progressOnStrip, clamped: true);
        Color result = Color.Lerp(Color.Lerp(Color.White, Color.Orange, transitToDark * 0.5f), Color.Red, lerpValue) * (1f - Utils.GetLerpValue(0f, 0.98f, progressOnStrip));
        result.A /= 8;
        return result;
    }
 
    private float StripWidth(float progressOnStrip)
    {
        float lerpValue = Utils.GetLerpValue(0f, 0.06f + transitToDark * 0.01f, progressOnStrip, clamped: true);
        lerpValue = 1f - (1f - lerpValue) * (1f - lerpValue);
        return MathHelper.Lerp(24f + transitToDark * 16f, 8f, Utils.GetLerpValue(0f, 1f, progressOnStrip, clamped: true)) * lerpValue;
    }
}