Ok, so what I'm trying to do is do fake lighting in a 2d game by making 2 textures, one with the normal screen information, and the second one a black and white texture where the "lights" are located. I'm having trouble getting the second texture set properly. I'm generating the second texture by rendering the white only sprites to a backbuffer, then saving the result of that to a texture. I know it's being generated properly, because when I use a function to save the texture to a file during the game, the save is what I'm expecting to see. I'm using the flatredball engine, and it handles setting the first texture as the rendered screen for me, I just need to figure out how to set the second texture. When I try to just output the second color in the shader, all I get is a completely blank screen. What am I doing wrong? The texture gets updated every frame. This is getting pretty frustrating .

The Shader Code:
// Shader Variable
float colorIntensity;

texture backTexture;

// Texture Sampler
//sampler2D inputSampler : register(s0);

sampler2D inputSampler;

sampler2D backSampler : register(s1) = sampler_state
{
texture = <backTexture>;
};

// Pixel Shader
float4 SaturateShader(float2 texCoord1 : TEXCOORD0) : COLOR
{
// Get the pixel's color
float4 color1 = tex2D(inputSampler, texCoord1);
float4 color2 = tex2D(backSampler, texCoord1);

// Return the saturated color
//color3 = color2 + .1f;
//color3 = color;
return color2;
}

// Technique
technique SetSaturation
{
pass Pass0
{
pixelShader = compile ps_2_0 SaturateShader();
}
}


The code that sets the second texture:
namespace Light.Entities
{
class PostProcessEffect : PostProcessingEffectBase
{
private Texture2D backTexture;
private float intensity;

public PostProcessEffect(String shader, Texture2D newBackTexture)
: base(shader)
{
backTexture = newBackTexture;
}

public override void InitializeEffect()
{
base.InitializeEffect();

mEnabled = true;
}

public void setIntensity(float intensityValue)
{
intensity = intensityValue;
}

public void updateTexture(Texture2D newBackTexture)
{
mEffect.Parameters["backTexture"].SetValue(newBackTexture);
}

protected override void SetEffectParameters(FlatRedBall.Camera camera)
{
mEffect.Parameters["colorIntensity"].SetValue(intensity);
mEffect.Parameters["backTexture"].SetValue(backTexture);
}
}
}

Edit: Never mind, I solved my problem through sheer luck.