My point is that a barebones ray tracer (spheres, planes, metal vs plastic) is much, much simpler than a barebones web browser (a minimal HTML parser + a minimal CSS parser and cascading + a minimal JS implementation + a miimal layout engine + a minimal renderer).

A text-only browser without scripting support, like lynx, could be a more reasonable project, but still larger than a basic ray tracer, or even a ray tracer + a basic material system.