燈光渲染效果低FPS

Question

我目前正在爲我的XNA遊戲開發一個類，用於渲染圖像上的燈光。當時，我已經讓源代碼繪製了我的光照貼圖，但是，我的來源中FPS非常低。我知道它在循環遍歷每個像素時被殘酷地減少了，但是，我不知道任何其他方式來讓我的紋理在XNA中設置每個像素，但使用「For」語句？

電流源：

public struct Light 
    { 
     public int Range; 
     public int Intensity; 
     public Color LightColor; 
     public Vector2 LightLocation; 

     public Light(int _Range, int _Intensity, Color _LightColor, Vector2 _LightLocation) 
     { 
      Range = _Range; 
      Intensity = _Intensity; 
      LightLocation = _LightLocation; 
      LightColor = _LightColor; 
     } 
    } 
    public class RenderClass 
    { 
     [System.Runtime.InteropServices.DllImport("User32.dll")] 
     public static extern bool MessageBox(IntPtr h, string S, string C, int a); 

     public static Texture2D RenderImage(Light[] LightLocations, Texture2D ScreenImage, Viewport v, bool ShadowBack = false) 
     { 
      Texture2D[] Images = new Texture2D[LightLocations.Count()]; 
      int curCount = 0; 

      /*LOOP THROUGHT EACH LIGHT*/ 
      foreach (Light LightLocation in LightLocations) 
      { 
       /*VARIABLES*/ 
       Color LightColor = LightLocation.LightColor; 
       int Range = LightLocation.Range; 
       int Intensity = LightLocation.Intensity; 

       /*GET COLORS*/ 
       int Width = v.Width; 
       int Height = v.Height; 
       Color[] Data = new Color[Width * Height]; 
       ScreenImage.GetData<Color>(Data); 

       /*VARIABLES TO SET COLOR*/ 
       Color[] SetColorData = new Color[Width * Height]; 

       /*CIRCEL*/ 
       int Radius = 15/2; // Define range to middle [Radius] 
       int Area = (int)Math.PI * (Radius * Radius); 

       for (int X = 0; X < Width; X++) 
       { 
        for (int Y = 0; Y < Height; Y++) 
        { 
         int Destination = X + Y * Width; 

         #region Light 
         /*GET COLOR*/ 
         Color nColor = Data[Destination]; 

         /*CREATE NEW COLOR*/ 
         Vector2 MiddlePos = new Vector2(LightLocation.LightLocation.X + Radius, LightLocation.LightLocation.Y + Radius); 
         Vector2 CurrentLocation = new Vector2(X, Y); 

         float Distance; 
         Distance = Vector2.Distance(MiddlePos, CurrentLocation); 
         Distance *= 100; 
         Distance /= MathHelper.Clamp(Range, 0, 100); 

         Vector3 newColors = nColor.ToVector3(); 

         nColor = new Color(
          newColors.X, 
          newColors.Y, 
          newColors.Z, 
          Distance/100); 


         /*SET COLOR*/ 
         SetColorData[Destination] = nColor; // Add to array 
         #endregion 
         #region Shadow 
         #endregion 
        } 
       } 


       ScreenImage.SetData<Color>(SetColorData); 
       Images[curCount] = ScreenImage; 
       curCount++; 
      } 

      return Images[0]; // Temporarily returning the first image of the array. 
     } 
    } 

正如你可以看到，這是一個緩慢而壞的方法。所以我想知道，有沒有更好的方法來設置每個像素&？

在此先感謝，dotTutorials！ =）

Answer 1

我認爲這項工作最好在像素着色器中完成。

您可以創建一次操作一盞燈的效果文件。
XNA使用DX9，因此您將被限制爲128個常量寄存器，我認爲您可以使用它來擠壓三盞燈。

因此，您將光照貼圖設置爲渲染目標，循環遍歷所有燈光，在效果上設置常量數據，渲染渲染目標大小的四邊形，並在像素着色器中計算光照方程。

在本質上類似的東西：

// In LoadContent 
RenderTarget2D lightmapRT = new RenderTarget2D(graphics.GraphicsDevice, 
               128, 
               128, 
               false, //No mip-mapping 
               SurfaceFormat.Color, 
               DepthFormat.Depth24); 

// We now render to the lightmap in Render method 
graphics.GraphicsDevice.SetRenderTarget(lightmapRT); 

// Lightmap is black by default 
graphics.GraphicsDevice.Clear(Color.Black); 

// Use the sprite batch to draw quads with custom shader 
spriteBatch.Begin(0, BlendState.Opaque, null, null, null, lightmapFx); 

foreach (var light in lights) 
{ 
    // Pass the light parameters to the shader 
    lightmapFx.Parameters["Viewport"].SetValue(new Vector2(GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height)); 
    lightmapFx.Parameters["Range"].SetValue(light.Range); 
    lightmapFx.Parameters["Intensity"].SetValue(light.Intensity); 
    lightmapFx.Parameters["LightColor"].SetValue(light.LightColor); 
    lightmapFx.Parameters["LightLocation"].SetValue(light.LightLocation); 

    // Render quad 
    spriteBatch.Draw(...); 
} 
spriteBatch.End(); 

與FX文件看起來類似的東西：

float Range; 
float Intensity; 
float3 LightColor; 
float2 LightLocation; 
float2 Viewport; 

struct VStoPS 
{ 
    float4 Position : POSITION0; 
    float2 TexCoord : TEXCOORD0; 
}; 

VStoPS VS(in float4 color : COLOR0, 
      in float2 texCoord : TEXCOORD0, 
      in float4 position : POSITION0) 
{ 
    VStoPS vsout = (VStoPS)0; 

    // Half pixel offset for correct texel centering. 
    vsout.Position.xy -= 0.5; 

    // Viewport adjustment. 
    vsout.Position.xy = position.xy/Viewport; 
    vsout.Position.xy *= float2(2, -2); 
    vsout.Position.xy -= float2(1, -1); 

    // Pass texcoords as is 
    vsout.TexCoord = texCoord; 

    return vsout; 
} 

float4 PS(VStoPS psin) 
{ 
    // Do calculations here 
    // Here I just set it to white 
    return float4(1.0f, 1.0f, 1.0f, 1.0f); 
} 

technique Main 
{ 
    pass p0 
    { 
     VertexShader = compile vs_3_0 VS(); 
     PixelShader = compile ps_3_0 PS(); 
    } 
} 

注意，這種非測試代碼，並可能完全錯誤的。我把它留給你來弄清楚在像素着色器中需要做什麼。