Stencil Buffer Portal Scenes

What this builds

A portal system where an arbitrarily shaped surface acts as a hole into a completely separate 3D world. The portal contents render at full framebuffer resolution with correct per-pixel depth, so objects can protrude through the opening and multiple portals can be on screen simultaneously without any of them costing a texture allocation.

• Arbitrary portal shape, defined by geometry rather than a rectangle
• Full native resolution, no render target, no DPR mismatch
• Correct depth interaction between the two worlds at the portal plane
• Multiple independent portals in one frame, each with its own world
• Objects that straddle the boundary, half in each world
• Backface handling so the portal disappears when viewed from behind

When to use / when not to