Alpha masks bounding box transparency clashing / overwriting with other alpha masks. XNA

Question

Above is an example of my problem. I have two alpha masks that are exactly the same, just a circle white gradient with transparent background.

I am drawing to a RenderTexture2D that is rendered above the screen to creating lighting. It clears a semi transparent black color, and then the alpha masks are drawn in the correct position to appear like lights..

On their own it works fine, but if two clash, like the below "torch" against the blue glowing mushrooms, you can see the bounding box transparency is overwriting the already drawn orange glow.

Here is my approach:

This is creating the render target:

RenderTarget2D = new RenderTarget2D(Global.GraphicsDevice, Global.Resolution.X+4, Global.Resolution.Y+4);
SpriteBatch = new SpriteBatch(Global.GraphicsDevice);

This is drawing to the render target:

private void UpdateRenderTarget()
    {
        Global.GraphicsDevice.SetRenderTarget(RenderTarget2D);
        Global.GraphicsDevice.Clear(ClearColor);

        // Draw textures
        float i = 0;
        foreach (DrawableTexture item in DrawableTextures)
        {
            i += 0.1f;
            item.Update?.Invoke(item);

            SpriteBatch.Begin(SpriteSortMode.Immediate, item.Blend,
           SamplerState.PointClamp, DepthStencilState.Default,
           RasterizerState.CullNone);

            SpriteBatch.Draw(
                item.Texture,
                (item.Position - Position) + (item.Texture.Size() / 2 * (1 - item.Scale)),
                null,
                item.Color,
                0,
                Vector2.Zero,
                item.Scale,
                SpriteEffects.None,
                i
            );
            SpriteBatch.End();
        }

        Global.GraphicsDevice.SetRenderTarget(null);
    }

I have heard about depth stencils etc.. and I feel like I have tried so many combinations of things but I am still getting the issue. I haven't had any troubles with this while building all the other graphics in my game.

Any help is greatly appreciated thanks! :)

Answer 1

Ah, this turned out to be a problem with the BlendState itself rather than the SpriteBatch. I had created a custom BlendState "Multiply" which I picked up online that was causing the issue.

"whats causing" the problem was the real question here.

This was the solution to get my effect without "overlapping":

public static BlendState Lighting = new BlendState
{
        ColorSourceBlend = Blend.One,
        ColorDestinationBlend = Blend.One,
        AlphaSourceBlend = Blend.Zero,
        AlphaDestinationBlend = Blend.InverseSourceColor
};

This allows the textures to overlap, and also "subtracts" from the "darkness" layer. It would be easier to see if the darkness was more opaque.

I have answered this just incase some other fool mistakes a blend state problem with the sprite batch itself.