Attempt #1

using System;
using System.Collections.Generic;
using System.Diagnostics;
using UnityEngine;
using Verse;
using RimWorld;

namespace M13Watermills
{
    [StaticConstructorOnStartup]
    public class CompTweakedWatermill : CompPowerPlantWater
    {
        private float spinPosition;

        public static readonly Material BladesMat = MaterialPool.MatFrom("Tweaked_WatermillBlades");

        public override void PostDraw()
        {
            base.PostDraw();
            Vector3 a = this.parent.TrueCenter();
            a += this.parent.Rotation.FacingCell.ToVector3() * 2.36f;
            for (int i = 0; i < 9; i++)
            {
                float num = this.spinPosition + 6.28318548f * (float)i / 9f;
                float x = Mathf.Abs(4f * Mathf.Sin(num));
                bool flag = num % 6.28318548f < 3.14159274f;
                Vector2 vector = new Vector2(x, 1f);
                Vector3 s = new Vector3(vector.x, 1f, vector.y);
                Matrix4x4 matrix = default(Matrix4x4);
                matrix.SetTRS(a + Vector3.up * 0.046875f * Mathf.Cos(num), this.parent.Rotation.AsQuat, s);
                Graphics.DrawMesh((!flag) ? MeshPool.plane10Flip : MeshPool.plane10, matrix, CompTweakedWatermill.BladesMat, 0);
            }
        }
    }

}