我正在尝试在应用程序中创建类似雾的效果，其中纹理（在上面的示例中为白色）在精灵周围变得透明（显示下面的黑色纹理），并且密度渐变远离它们的中心。但是，每当我向 alpha 蒙版添加一个新圆圈时，它都会覆盖先前添加到蒙版纹理中的内容，从而产生如上图所示的不和谐效果。我一直在尝试为蒙版纹理添加新内容，以便与之前添加的内容很好地融合，但我不知道该怎么做。
我尝试过做一些事情，比如为我的遮罩创建一个遮罩以与之混合，但它总是什么都不显示，或者使用我的 alpha 着色器 fx 文件绘制到我的 alpha 遮罩（这会产生一些非常奇怪的视觉效果）
如何将添加到 alpha 蒙版的内容混合在一起，以免它们相互覆盖？
非常感谢任何帮助。
- - - - - - -代码： - - - - - - -
在此方法中完成 alpha 掩码的更新：
public void createLightSource(Vector2 RemovePosition, Texture2D circleTexture)
{
// Create a render target, which we will draw to instead of the screen
RenderTarget2D target = new RenderTarget2D(graphics.GraphicsDevice, mainTexture.Width, mainTexture.Height);
// set the RenderTarget2D as the target for all future Draw calls untill we say otherwise
graphics.GraphicsDevice.SetRenderTarget(target);
// start our batch as usual..
spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.PointClamp, null, null);
// start with a transparent canvas
graphics.GraphicsDevice.Clear(Color.Transparent);
// add in the previously drawn dots from the current alpha map.
spriteBatch.Draw(alphaMask, new Vector2(0, 0), null, Color.White, 0f, Vector2.Zero, 1f, SpriteEffects.None, 1f);
// add a new dot to the map.
play.game.spriteBatch.Draw(circleTexture,
new Vector2((float)(RemovePosition.X - mainTexture.x), (float)(RemovePosition.Y - mainTexture.y)),
null,
Color.White,
0f,
new Vector2(circleTexture.Width / 2f, circleTexture.Height / 2f),
1f,
SpriteEffects.None,
1f);
// end the draw call
spriteBatch.End();
// start drawing to the screen again
graphics.GraphicsDevice.SetRenderTarget(null);
// set our Texture2D Alpha Mask to equal the current render target (the new mask).
// RenderTarget2D can be cast to a Texture2D without a problem
alphaMask = target;
}
使用以下方法绘制主纹理：
public void mainTextureDraw()
{
//alpha shader is the fx file (below)
alphaShader.Parameters["MaskTexture"]
.SetValue(alphaMask);
// start a spritebatch for our effect
spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend,
null, null, null, alphaShader);
play.game.spriteBatch.Draw(mainTexture,
position,
null, Color.White, 0f,
new Vector2(0, 0),
1f, SpriteEffects.None, 1f);
spriteBatch.End();
}
以及fx文件中的重要方法：
float4 PixelShaderFunction(float2 inCoord: TEXCOORD0) : COLOR
{
// we retrieve the color in the original texture at
// the current coordinate remember that this function
// is run on every pixel in our texture.
float4 color = tex2D(mainTexture, inCoord);
// Since we are using a black and white mask the black
// area will have a value of 0 and the white areas will
// have a value of 255. Hence the black areas will subtract
// nothing from our original color, and the white areas of
// our mask will subtract all color from the color.
color.rgba = color.rgba - tex2D(alphaMask, inCoord).r;
// return the new color of the pixel.
return color;
}