Second spriteBatch.Draw() always turns textures Red

Graphics
1

I’m using the following code to test shaders (Lightning Engine) but my second spritebatch.Draw() call turns the textures to red

in my Game1 class i use the following code to draw the scene:

 GraphicsDevice.Clear(Color.CornflowerBlue);
 LightEffect.Parameters["lightMapSampler"].SetValue(LightMap);
            spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend, null, null, null, LightEffect);
            spriteBatch.Draw(Background, new Rectangle(0,0, GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height), Color.White);
            spriteBatch.End();
            GraphicsDevice.Textures[1] = null;
            spriteBatch.Begin();
            spriteBatch.Draw(MidGround, new Rectangle(0, 0, GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height), Color.White);
            spriteBatch.End();

The code is based on the following “tutorial” http://rabidlion.com/?p=11 I’m using the same textures as well. The shader looks like this:

sampler textureSampler : register(s0);

sampler lightMapSampler : register(s1);


float4 PixelShaderFunction(float2 texcoords  : TEXCOORD0) : COLOR0
{
    float4 backgroundCol = tex2D(textureSampler, texcoords);
    float4 lightMapCol = tex2D(lightMapSampler, texcoords);
    return backgroundCol * lightMapCol;
}

technique Light
{
    pass BasicLight
    {
        PixelShader = compile ps_2_0 PixelShaderFunction();
    }
}

Now my midground isn’t grey after drawing it. the texture turns red:

RedTextureProblem.png816×518 80.5 KB

I’m using Monogame 3.4 on a Windows 7 64 bit.

What is my mistake? Is this a Monogame bug?

I already got this Problem with Monogame 3.2 Problem with HLSL Shaders in Monogame V 3.2 but didn’t try anymore since then … shame on me and sorry tom but thanks for the help anyway.

Update

If I stop to apply the shader the colors are normal. (Background and Midground, Lightmap doesn’t get drawed).

Update 2

If I change my second render to the following:

            spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend, null, null, null, DefaultEffect);
            spriteBatch.Draw(MidGround, new Rectangle(0, 0, GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height), Color.White);
spriteBatch.End();

It just works fine. The DefaultEffect looks like this:

sampler TextureSampler : register(s0);

float4 main(float4 position : SV_Position, float4 color : COLOR0, float2 texCoord : TEXCOORD0) : COLOR0
{
    float4 tex = tex2D(TextureSampler, texCoord);
    return tex;
}


technique Technique1
{
    pass Pass1
    {
        PixelShader = compile ps_3_0 main();
    }
}

If I change the return of the shader to:

return tex * color;

the textures are red again.