从深度重建世界立场是错误的 [英] reconstructed world position from depth is wrong

问题描述

我正在尝试实施延迟的阴影/照明.为了减少缓冲区的数量/大小，我想稍后使用深度纹理来重建世界位置.

I'm trying to implement deferred shading/lighting. In order to reduce the number/size of the buffers I use I wanted to use the depth texture to reconstruct world position later on.

我通过将像素坐标乘以投影矩阵的逆和相机矩阵的逆来实现.这种工作，但位置有点偏离.这是采样的世界位置纹理的绝对差异:

I do this by multiplying the pixel's coordinates with the inverse of the projection matrix and the inverse of the camera matrix. This sort of works, but the position is a bit off. Here's the absolute difference with a sampled world position texture:

作为参考，这是我在第二遍片段着色器中使用的代码:

For reference, this is the code I use in the second pass fragment shader:

vec2 screenPosition_texture = vec2((gl_FragCoord.x)/WIDTH, (gl_FragCoord.y)/HEIGHT);
float pixelDepth = texture2D(depth, screenPosition_texture).x;

vec4 worldPosition = pMatInverse*vec4(VertexIn.position, pixelDepth, 1.0);
worldPosition = vec4(worldPosition.xyz/worldPosition.w, 1.0);
//worldPosition /= 1.85;
worldPosition = cMatInverse*worldPosition_byDepth;

如果我取消对worldPosition/= 1.85的注释，则该位置的重建会更好(在我的几何图形/深度值范围内).在将输出与应有的值进行比较之后(在第三个纹理中存储)，我搞砸了才得到了这个值.

If I uncomment worldPosition /= 1.85, the position is reconstructed a lot better (on my geometry/range of depth values). I just got this value by messing around after comparing my output with what it should be (stored in a third texture).

我正在使用0.1近距离，100.0远距离，而我的几何图形最多可达约15远距离. 我知道可能存在精度错误，但这似乎太接近相机了，误差太大了. 我在这里想念任何东西吗?

I'm using 0.1 near, 100.0 far and my geometries are up to about 15 away. I know there may be precision errors, but this seems a bit too big of an error too close to the camera. Did I miss anything here?

推荐答案

如评论中所述: 我没有将深度值从ndc空间转换为剪辑空间. 我应该添加以下行:

As mentioned in a comment: I didn't convert the depth value from ndc space to clip space. I should have added this line:

pixelDepth=pixelDepth*2.0-1.0;

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