I'm currently working on adding a reflective surface to my project. I have most of it down and working properly, but I am struggling with a technique I've read about online (and which seems to be widely used). I'm referring to this technique: "Modifying the Projection Matrix to Perform Oblique Near-Plane Clipping". Without the technique, I'm able to render my reflective surface correctly, but only if I delete all of the objects behind the reflection plane. I'm aware that I could add some code into my pixel shader to clip fragments that are behind the custom clipping plane, but I'd like to avoid doing that if I can.
Without the oblique near plane: https://i.imgur.com/ZxnwKNX.jpg
I've followed several different versions of the technique linked above, but I can't seem to get it right. Invariably, I end up with weird distortions like this:
The last little "preview image" at the top shows the rendered reflection view. You can see that the reflected view is completely warped, and stretches out infinitely rather than just having a regular upside-down perspective.
The function that modifies the projection matrix is really small, so I'm not sure where my mistake is. The one thing I've modified from the link above is I am scaling the clip plane by (1 / dot(clip, q)) instead of (2 / dot(clip, q)), and removed a +1 at the end, because I am using a [0, 1] clip space. I've seen this mentioned in some places online. Regardless, it doesn't help to change that back. Can anyone point me in the right direction here? The relevant code can be seen here. Any help would be much appreciated.
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