BrushVolume

using SharpDX;
using SharpDX.Direct3D11;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace VoidwalkerEngine.Framework.DirectX.Rendering
{

    public enum FaceVisibilityOptions
    {
        None = 0,
        Front = 1,
        Back = 2,
        Left = 4,
        Right = 8,
        Top = 16,
        Bottom = 32,
        All = Front | Back | Left | Right | Top | Bottom
    }

    public class BrushVolume
    {
        public Vector3 Location { get; set; }
        public int Width { get; private set; }
        public int Height { get; private set; }
        public int Depth { get; private set; }
        public FaceVisibilityOptions FaceVisibility { get; private set; }
        public Material DiffuseMaterial { get; set; }
        public Device Device;
        private Buffer _vertexBuffer;
        private const float _stride = 16;
        // 36 Vertices maximum
        private int _drawCount;

        public BrushVolume(Device device, Material diffuseMaterial,
            int width, int height, int length,
            FaceVisibilityOptions visibilityOptions)
        {
            this.Device = device;
            this.Width = width;
            this.Height = height;
            this.Depth = length;
            this.FaceVisibility = visibilityOptions;
            this.DiffuseMaterial = diffuseMaterial;
            Rebuild();
        }

        public void Resize(int width, int height, int depth)
        {
            this.Width = width;
            this.Height = height;
            this.Depth = depth;
            Rebuild();
        }

        public void Rebuild(int width, int height, int depth, FaceVisibilityOptions visibilityOptions)
        {
            this.Width = width;
            this.Height = height;
            this.Depth = depth;
            this.FaceVisibility = visibilityOptions;
            Rebuild();
        }

        public void SetFaceVisibility(FaceVisibilityOptions visibilityOptions)
        {
            this.FaceVisibility = visibilityOptions;
            Rebuild();
        }

        private int CountVisibleFaces(FaceVisibilityOptions visibilityOptions)
        {
            int value = (int)visibilityOptions;
            value -= ((value >> 1) & 1431655765);
            value = (value & 858993459) + ((value >> 2) & 858993459);
            int count = ((value + (value >> 4) & 252645135) * 16843009) >> 24;
            return count;
        }

        public void Rebuild()
        {
            Vertex[] vertices = new Vertex[CountVisibleFaces(this.FaceVisibility) * 6];
            float width = _stride * this.Width;
            float height = _stride * this.Height;
            float depth = _stride * this.Depth;
            float uvX = width / _stride;
            float uvY = height / _stride;
            float uvZ = depth / _stride;
            // Generate Front Face
            int index = 0;
            if (this.FaceVisibility.HasFlag(FaceVisibilityOptions.Front))
            {
                Vector3 normal = new Vector3(0, 0, -1);
                vertices[index++] = new Vertex(new Vector3(-width, height, -depth), new Vector2(-uvX, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(width, -height, -depth), new Vector2(0, 0), normal);
                vertices[index++] = new Vertex(new Vector3(-width, -height, -depth), new Vector2(-uvX, 0), normal);
                vertices[index++] = new Vertex(new Vector3(-width, height, -depth), new Vector2(-uvX, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(width, height, -depth), new Vector2(0, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(width, -height, -depth), new Vector2(0, 0), normal);
            }
            // Generate Back Face
            if (this.FaceVisibility.HasFlag(FaceVisibilityOptions.Back))
            {
                Vector3 normal = new Vector3(0, 0, 1);
                vertices[index++] = new Vertex(new Vector3(width, height, depth), new Vector2(-uvX, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(-width, -height, depth), new Vector2(0, 0), normal);
                vertices[index++] = new Vertex(new Vector3(width, -height, depth), new Vector2(-uvX, 0), normal);
                vertices[index++] = new Vertex(new Vector3(width, height, depth), new Vector2(-uvX, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(-width, height, depth), new Vector2(0, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(-width, -height, depth), new Vector2(0, 0), normal);
            }

            // Generate Right Face
            if (this.FaceVisibility.HasFlag(FaceVisibilityOptions.Right))
            {
                Vector3 normal = new Vector3(1, 0, 0);
                vertices[index++] = new Vertex(new Vector3(width, height, -depth), new Vector2(-uvZ, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(width, -height, depth), new Vector2(0, 0), normal);
                vertices[index++] = new Vertex(new Vector3(width, -height, -depth), new Vector2(-uvZ, 0), normal);
                vertices[index++] = new Vertex(new Vector3(width, height, -depth), new Vector2(-uvZ, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(width, height, depth), new Vector2(0, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(width, -height, depth), new Vector2(0, 0), normal);
            }

            // Generate Left Face
            if (this.FaceVisibility.HasFlag(FaceVisibilityOptions.Left))
            {
                Vector3 normal = new Vector3(-1, 0, 0);
                vertices[index++] = new Vertex(new Vector3(-width, height, depth), new Vector2(-uvZ, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(-width, -height, -depth), new Vector2(0, 0), normal);
                vertices[index++] = new Vertex(new Vector3(-width, -height, depth), new Vector2(-uvZ, 0), normal);
                vertices[index++] = new Vertex(new Vector3(-width, height, depth), new Vector2(-uvZ, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(-width, height, -depth), new Vector2(0, -uvY), normal);
                vertices[index++] = new Vertex(new Vector3(-width, -height, -depth), new Vector2(0, 0), normal);
            }

            // Generate Bottom Face
            if (this.FaceVisibility.HasFlag(FaceVisibilityOptions.Bottom))
            {
                Vector3 normal = new Vector3(0, -1, 0);

                vertices[index++] = new Vertex(new Vector3(-width, -height, depth), new Vector2(-uvZ, -uvX), normal);
                vertices[index++] = new Vertex(new Vector3(width, -height, -depth), new Vector2(0, 0), normal);
                vertices[index++] = new Vertex(new Vector3(width, -height, depth), new Vector2(-uvZ, 0), normal);
                vertices[index++] = new Vertex(new Vector3(-width, -height, depth), new Vector2(-uvZ, -uvX), normal);
                vertices[index++] = new Vertex(new Vector3(-width, -height, -depth), new Vector2(0, -uvX), normal);
                vertices[index++] = new Vertex(new Vector3(width, -height, -depth), new Vector2(0, 0), normal);
            }

            // Generate Top Face
            if (this.FaceVisibility.HasFlag(FaceVisibilityOptions.Top))
            {
                Vector3 normal = new Vector3(0, 1, 0);

                vertices[index++] = new Vertex(new Vector3(width, height, depth), new Vector2(-uvZ, -uvX), normal);
                vertices[index++] = new Vertex(new Vector3(-width, height, -depth), new Vector2(0, 0), normal);
                vertices[index++] = new Vertex(new Vector3(-width, height, depth), new Vector2(-uvZ, 0), normal);
                vertices[index++] = new Vertex(new Vector3(width, height, depth), new Vector2(-uvZ, -uvX), normal);
                vertices[index++] = new Vertex(new Vector3(width, height, -depth), new Vector2(0, -uvX), normal);
                vertices[index++] = new Vertex(new Vector3(-width, height, -depth), new Vector2(0, 0), normal);
            }
            if (this._vertexBuffer != null)
            {
                this._vertexBuffer.Dispose();
            }
            this._drawCount = vertices.Length;
            _vertexBuffer = Buffer.Create(Device, BindFlags.VertexBuffer, vertices);
        }

        public void Draw(DeviceContext context)
        {
            context.InputAssembler.SetVertexBuffers(0, new VertexBufferBinding(this._vertexBuffer, Marshal.SizeOf<Vertex>(), 0));
            if (DiffuseMaterial != null)
            {
                context.PixelShader.SetShaderResource(0, DiffuseMaterial.ResourceView);
                context.PixelShader.SetSampler(0, DiffuseMaterial.SamplerState);
            }
            context.Draw(_drawCount, 0);
        }

    }
}