float g_fBlurAmount = 1.0f;float4x4 g_matInvView;float4x4 g_matLastViewProj;float4 MotionBlurPS (	in float2 in_vTexCoord		: TEXCOORD0,		        in float3 in_vFrustumPlaneVS	: TEXCOORD1,			uniform int iNumSamples		)	: COLOR0 {	// Reconstruct view-space position from the depth buffer	float fPixelDepthVS = tex2D(PointSampler1, in_vTexCoord).x;	float3 vPixelPositionVS = fPixelDepthVS * in_vFrustumPlaneVS;	// Convert to world-space, then determine the the  clip-space	// position of the pixel in the previous frame.	float4 vPixelPositionWS = mul(float4(vPixelPositionVS, 1.0f), g_matInvView);	float4 vLastPixelPosCS = mul(vPixelPositionWS, g_matLastViewProj);	// Find the corresponding texture coordinate	float2 vLastTexCoord = vLastPixelPosCS.xy / vLastPixelPosCS.w;    vLastTexCoord = (vLastTexCoord / 2.0f) + 0.5f;    vLastTexCoord.y = 1.0f - vLastTexCoord.y;    vLastTexCoord += 1.0f / g_vDestinationDimensions;	float2 vPixelVelocity = in_vTexCoord - vLastTexCoord;		// Clamp to a max velocity.  The max we can go without artifacts os	// is 1.4f * iNumSamples...but we can fudge things a little.	float2 maxVelocity = (2.0f * iNumSamples) / g_vSourceDimensions;	vPixelVelocity = clamp(vPixelVelocity, -maxVelocity, maxVelocity);		float2 vFinalSamplePos = in_vTexCoord + vPixelVelocity;    // For each sample, sum up each sample's color in "vSum" and then divide    // to average the color after all the samples are added.    float4 vSum = 0;        for(int i = 0; i < iNumSamples; i++)    {           // Sample texture in a new spot based on vPixelVelocity vector         // and average it with the other samples        float2 vTexCoord = lerp(in_vTexCoord, vFinalSamplePos, (i  / (float)iNumSamples));                        // Lookup the color at this new spot        float4 vSample = tex2D(PointSampler0, vTexCoord);                // Add it with the other samples        vSum += vSample;    }        // Return the average color of all the samples    return vSum / (float)iNumSamples;}