Render Target Portal Windows

What this builds

A portal implemented as a texture: a second camera renders another scene into a WebGLRenderTarget, and that target is sampled by a material on the portal surface. The result is a framed window into another world that composes cleanly with post-processing, supports blur and distortion on the portal surface itself, and can be blended or animated as an ordinary texture.

• Any surface shape via UV mapping or an alpha mask
• Correct perspective from the viewer's position, not a flat billboard
• Post-processing on the portal contents independently of the main scene
• Smooth open and close transitions by blending the target
• R3F path using drei MeshPortalMaterial, and a vanilla path

When to use / when not to