SSAO阴影移动奇怪与相机(计算gbuffer错误)

Question

我试图用本教程实现这个版本的ssao：

http://www.learnopengl.com/#!Advanced-Lighting/SSAO

这里是我的渲染纹理结束的结果。

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当我移动相机时，阴影似乎跟着我。

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好像我错过了某种矩阵乘法的相机。

代码

gBuffer顶点

#version 330 core
layout (location = 0) in vec3 vertexPosition;
layout (location = 1) in vec3 vertexNormal;

out vec3 position;
out vec3 normal;

uniform mat4 m;
uniform mat4 v;
uniform mat4 p;
uniform mat4 n;

void main()
{
    vec4 viewPos = v * m * vec4(vertexPosition, 1.0f);
    position = viewPos.xyz;
    gl_Position = p * viewPos;
    normal = vec3(n * vec4(vertexNormal, 0.0f));
}

gBuffer片段

#version 330 core
layout (location = 0) out vec4 gPosition;
layout (location = 1) out vec3 gNormal;
layout (location = 2) out vec4 gColor;

in vec3 position;
in vec3 normal;

const float NEAR = 0.1f;
const float FAR = 50.0f;
float LinearizeDepth(float depth)
{
    float z = depth * 2.0f - 1.0f;
    return (2.0 * NEAR * FAR) / (FAR + NEAR - z * (FAR - NEAR));
}

void main()
{   
    gPosition.xyz = position;
    gPosition.a = LinearizeDepth(gl_FragCoord.z);
    gNormal = normalize(normal);
    gColor.rgb = vec3(1.0f);
}

SSAO顶点

#version 330 core

layout (location = 0) in vec3 vertexPosition;
layout (location = 1) in vec2 texCoords;

out vec2 UV;

void main(){
    gl_Position =  vec4(vertexPosition, 1.0f);
    UV = texCoords;
}

SSAO片段

#version 330 core

out float FragColor;
in vec2 UV;

uniform sampler2D gPositionDepth;
uniform sampler2D gNormal;
uniform sampler2D texNoise;
uniform vec3 samples[32];
uniform mat4 projection;

// parameters (you'd probably want to use them as uniforms to more easily tweak the effect)
int kernelSize = 32;
float radius = 1.0;

// tile noise texture over screen based on screen dimensions divided by noise size
const vec2 noiseScale = vec2(1024.0f/4.0f, 1024.0f/4.0f);

void main()
{
    // Get input for SSAO algorithm
    vec3 fragPos = texture(gPositionDepth, UV).xyz;
    vec3 normal = texture(gNormal, UV).rgb;
    vec3 randomVec = texture(texNoise, UV * noiseScale).xyz;
    // Create TBN change-of-basis matrix: from tangent-space to view-space
    vec3 tangent = normalize(randomVec - normal * dot(randomVec, normal));
    vec3 bitangent = cross(normal, tangent);
    mat3 TBN = mat3(tangent, bitangent, normal);
    // Iterate over the sample kernel and calculate occlusion factor
    float occlusion = 0.0;
    for(int i = 0; i < kernelSize; ++i)
    {
        // get sample position
        vec3 sample = TBN * samples[i]; // From tangent to view-space
        sample = fragPos + sample * radius;

        // project sample position (to sample texture) (to get position on screen/texture)
        vec4 offset = vec4(sample, 1.0);
        offset = projection * offset; // from view to clip-space
        offset.xyz /= offset.w; // perspective divide
        offset.xyz = offset.xyz * 0.5 + 0.5; // transform to range 0.0 - 1.0

       // get sample depth
        float sampleDepth = -texture(gPositionDepth, offset.xy).w; // Get depth value of kernel sample

        // range check & accumulate
        float rangeCheck = smoothstep(0.0, 1.0, radius / abs(fragPos.z - sampleDepth ));
        occlusion += (sampleDepth >= sample.z ? 1.0 : 0.0) * rangeCheck;
    }
    occlusion = 1.0 - (occlusion / kernelSize);
    FragColor = occlusion;
}

我四处阅读，看到有人有类似的问题，并将视图矩阵传递到ssao着色器中，并放大了sampleDepth：

float sampleDepth = (viewMatrix * -texture(gPositionDepth, offset.xy)).w;

但似乎这只会让事情变得更糟。

这是另一幅从上到上的视图，你可以看到阴影随着摄像机的移动。

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如果我用某种方式定位我的相机，事情就会排列起来

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Answer 1

虽然我只能在n顶点着色器中假定你的法线矩阵的值，但似乎你不把法线存储在视图空间中，而是在世界空间。由于SSAO计算是在屏幕空间中完成的，这可以(至少部分)解释意外行为。在这种情况下，您要么需要将视图矩阵v乘以法线，然后再将它们存储到gBuffer (可能更有效，但可能会干扰其他阴影计算)，或者在检索它们之后。