Variance shadow Maps - Gaussian blur not working

@YTN wrote:

Anyone have a working sample of VSMs?

I have been trying to get this working, but am hitting a roadblock. My Gaussian blur seems to render my shadowmap empty / blank.

Here's how I am creating the blur render target:

            _blurMap = new RenderTarget2D(AxisGame.Instance.GraphicsDevice, 2048, 2048, false, SurfaceFormat.Color, DepthFormat.Depth24);

And here's the actual blur shader... this is straight out of the book "3D Graphics with XNA Game Studio 4.0" by Sean James (great book!).

texture Texture;

sampler2D TextureSampler = sampler_state
{
	texture = <Texture>;
	minfilter = point;
	magfilter = point;
	mipfilter = point;
};

// precalculated weights and offsets
float weights[15] =
{
	0.1061154, 0.1028506, 0.1028506, 0.09364651, 0.09364651,
	0.0801001, 0.0801001, 0.06436224, 0.06436224, 0.04858317,
	0.04858317, 0.03445063, 0.03445063, 0.02294906, 0.02294906
};

float offsets[15] =
{
	0, 0.00125, -0.00125, 0.002916667, -0.002916667,
	0.004583334, -0.004583334,0.00625, -0.00625, 0.007916667,
	-0.007916667, 0.009583334, -0.009583334, 0.01125, -0.01125
};


float4 BlurHorizontal(float4 position : POSITION0, float4 color : COLOR0, float2 texCoord : TEXCOORD0) : Color0
{
	float4 output = float4(0, 0, 0, 1);

	for (int i = 0; i < 15; i++)
	{
		output += tex2D(TextureSampler, texCoord + float2(offsets[i], 0)) * weights[i];
	}

	return output;
}


float4 BlurVertical(float4 position : POSITION0, float4 color : COLOR0, float2 texCoord : TEXCOORD0) : Color0
{
	float4 output = float4(0, 0, 0, 1);

	for (int i = 0; i < 15; i++)
	{
		output += tex2D(TextureSampler, texCoord + float2(0, offsets[i])) * weights[i];
	}

	return output;
}


technique Blur
{
	pass Horizontal
	{
#if SM4	
		PixelShader = compile ps_4_0 BlurHorizontal();
#else
		PixelShader = compile ps_3_0 BlurHorizontal();
#endif
	}

	pass Vertical
	{
#if SM4	
		PixelShader = compile ps_4_0 BlurVertical();
#else
		PixelShader = compile ps_3_0 BlurVertical();
#endif
	}
}

Here's my draw code... note, _shadowMap has already been created (with the models already rendered to it), and it works perfectly without VSM. This code was added and uses _shadowMap as the source to blur it per VSM:

    // blur shadow
    var blurEffect = GaussianBlurEffect;
    blurEffect.CurrentTechnique = blurEffect.Techniques["Blur"];

    GraphicsDevice.SetRenderTarget(_blurMap);
    GraphicsDevice.Clear(Color.White);

    // horizontal
    SpriteBatch.Begin(SpriteSortMode.Immediate, BlendState.Opaque);
    blurEffect.CurrentTechnique.Passes[0].Apply();
    SpriteBatch.Draw(_shadowMap, Vector2.Zero, Color.White);
    SpriteBatch.End();

    GraphicsDevice.SetRenderTarget(_shadowMap);
    GraphicsDevice.Clear(Color.White);

    // vertical
    SpriteBatch.Begin(SpriteSortMode.Immediate, BlendState.Opaque);
    blurEffect.CurrentTechnique.Passes[1].Apply();
    SpriteBatch.Draw(_blurMap, Vector2.Zero, Color.White);
    SpriteBatch.End();

    GraphicsDevice.SetRenderTarget(null);
    GraphicsDevice.BlendState = BlendState.Opaque;
    GraphicsDevice.DepthStencilState = DepthStencilState.Default;

Anyone have any ideas as to why this isn't working? The final shadowmap ends up black...

Thanks!

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