One of the advantages of orthographic mode is that the back/front silhouette is the same. Not true for perspective, however I do need to render two sides of an object in perspective such that the silhouettes are the same.

Ideally I would just invert the normals so that the backside would show, but this is not quite right due to internal volumes and such becoming visible. I think what I need is like the diagram below: when each camera ray hits the surface, it would travel parallel to the center ray to the other side of the object, then use the color of that surface instead of the hit surface.

enter image description here

Does anyone know how I could achieve this?

Adding an example render of Suzanne showing the problem of things not lining up due to perspective. I feel that ultimately its about what color is each pixel, so I want the back pixels' color to be used instead of front pixels.

enter image description here enter image description here

  • $\begingroup$ Can you possibly post some screenshots of the scene and object that you are trying to record and some of the outcomes from what you've tried vs. your expectations? This diagram alone is kind of confusing as to what you're trying to achieve. $\endgroup$
    – Jakemoyo
    May 25, 2022 at 12:45
  • $\begingroup$ @Jakemoyo - added images $\endgroup$
    – Karric
    May 25, 2022 at 13:31
  • $\begingroup$ You could try rendering two images with one camera each in perspective and orthographic mode, and then use the alpha from one image to mask the other. This is kind of stretching the limits of reality though and I don't think you will be able to get them to line up perfectly. That's just kind of the nature of the difference between perspective and ortho viewpoints. $\endgroup$
    – Jakemoyo
    May 26, 2022 at 8:50


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