DirectX Shader无法正常工作？

Question

Okay so I have this shader for ambient occlusion. It loads to world correctly, but it just shows all the models as being white. I do not know why. I am just running the shader while the model is rendering, is that correct? or do I need to make a render target or something? if so then how? I'm using C++. Here is my shader.

float sampleRadius;
float distanceScale;
float4x4 xProjection;
float4x4 xView;
float4x4 xWorld;

float3 cornerFustrum;

struct VS_OUTPUT
{
    float4 pos              : POSITION;
    float2 TexCoord         : TEXCOORD0;
    float3 viewDirection    : TEXCOORD1;
}; 

VS_OUTPUT VertexShaderFunction(
    float4 Position : POSITION, float2 TexCoord : TEXCOORD0)
{
    VS_OUTPUT Out = (VS_OUTPUT)0;

    float4 WorldPosition = mul(Position, xWorld);
    float4 ViewPosition = mul(WorldPosition, xView);
    Out.pos = mul(ViewPosition, xProjection);
    Position.xy = sign(Position.xy);
    Out.TexCoord = (float2(Position.x, -Position.y) + float2( 1.0f, 1.0f ) ) * 0.5f;
    float3 corner = float3(-cornerFustrum.x * Position.x,
            cornerFustrum.y * Position.y, cornerFustrum.z);
    Out.viewDirection =  corner;

    return Out;
}


texture depthTexture;
texture randomTexture;

sampler2D depthSampler = sampler_state
{
    Texture = <depthTexture>;
    ADDRESSU = CLAMP;
    ADDRESSV = CLAMP;
    MAGFILTER = LINEAR;
    MINFILTER = LINEAR;
};

sampler2D RandNormal = sampler_state
{
    Texture = <randomTexture>;
    ADDRESSU = WRAP;
    ADDRESSV = WRAP;
    MAGFILTER = LINEAR;
    MINFILTER = LINEAR;
};

float4 PixelShaderFunction(VS_OUTPUT IN) : COLOR0
{
    float4 samples[16] =
    {
        float4(0.355512,    -0.709318,  -0.102371,  0.0 ),
        float4(0.534186,    0.71511,    -0.115167,  0.0 ),
        float4(-0.87866,    0.157139,   -0.115167,  0.0 ),
        float4(0.140679,    -0.475516,  -0.0639818, 0.0 ),
        float4(-0.0796121,  0.158842,   -0.677075,  0.0 ),
        float4(-0.0759516,  -0.101676,  -0.483625,  0.0 ),
        float4(0.12493,     -0.0223423, -0.483625,  0.0 ),
        float4(-0.0720074,  0.243395,   -0.967251,  0.0 ),
        float4(-0.207641,   0.414286,   0.187755,   0.0 ),
        float4(-0.277332,   -0.371262,  0.187755,   0.0 ),
        float4(0.63864,     -0.114214,  0.262857,   0.0 ),
        float4(-0.184051,   0.622119,   0.262857,   0.0 ),
            float4(0.110007,    -0.219486,  0.435574,   0.0 ),
        float4(0.235085,    0.314707,   0.696918,   0.0 ),
        float4(-0.290012,   0.0518654,  0.522688,   0.0 ),
        float4(0.0975089,   -0.329594,  0.609803,   0.0 )
    };

    IN.TexCoord.x += 1.0/1600.0;
    IN.TexCoord.y += 1.0/1200.0;

    normalize (IN.viewDirection);
    float depth = tex2D(depthSampler, IN.TexCoord).a;
    float3 se = depth * IN.viewDirection;

    float3 randNormal = tex2D( RandNormal, IN.TexCoord * 200.0 ).rgb;

    float3 normal = tex2D(depthSampler, IN.TexCoord).rgb;
    float finalColor = 0.0f;

    for (int i = 0; i < 16; i++)
    {
        float3 ray = reflect(samples[i].xyz,randNormal) * sampleRadius;

        //if (dot(ray, normal) < 0)
        //  ray += normal * sampleRadius;

        float4 sample = float4(se + ray, 1.0f);
        float4 ss = mul(sample, xProjection);

        float2 sampleTexCoord = 0.5f * ss.xy/ss.w + float2(0.5f, 0.5f);

        sampleTexCoord.x += 1.0/1600.0;
        sampleTexCoord.y += 1.0/1200.0;
        float sampleDepth = tex2D(depthSampler, sampleTexCoord).a;

        if (sampleDepth == 1.0)
        {
            finalColor ++;
        }
        else
        {       
            float occlusion = distanceScale* max(sampleDepth - depth, 0.0f);
            finalColor += 1.0f / (1.0f + occlusion * occlusion * 0.1);
        }
    }

    return float4(finalColor/16, finalColor/16, finalColor/16, 1.0f);
}


technique SSAO
{
    pass P0
    {          
        VertexShader = compile vs_3_0 VertexShaderFunction();
        PixelShader  = compile ps_3_0 PixelShaderFunction();
    }
}

Answer 1

To answer the core question: this shader is for render target processing -- you need the depth buffer to be filled before running it. It's not for rendering on the model surfaces.