Hi, I'm currently working on a project in that area. The main workflow in the system is take a bunch of pictures, SIFT & match them, then generate a sparse model of 2d features (image coords), 3d features (point cloud in relative coords) and camera positions. We then shard and re-combine different models to synthesize larger or more precise reconstructions. I'm building with clojurescript & Three.js[0] in the frontend, and can recommend the stack

Back to your comment I'd love to hear what you're looking to do and what you'd need, sounds like I may have explored the same problem space.

[0] https://threejs.org/

About building the 3D model:

There is Regard3D, if by barriers to entry you mean sensor hardware: http://www.regard3d.org/index.php/documentation/introduction

If by barriers to entry you mean technical skills, there are SaaS solutions like Beholder: https://beholder.vision/

About embedding the demo in a web page, I have no idea.

Maybe find some demos in the engine of your choice then import the model in?