Arnold Material Creation Improvements

[mistafunk]

note: some of the commits are a bit evolutionary/overlapping

[jonathan-meier]

please avoid mixing renaming changes with changes to the logic (last commit aed5e0e)

Apart from the minor things mentioned in the inline commits, this is looking very good. I did a small functional test and the deduplication worked.

[jonathan-meier]

only some small stuff left, can be merged directly afterwards

I especially like the changes for letting Maya uniqueify node names 👍

[jonathan-meier]

shouldn't this be matStream->elementCount() != 1?

[mistafunk]

done

[jonathan-meier]

consider returning the definite shading engine name separately instead of using an in-out parameter for better readability

[mistafunk]

done

[jonathan-meier]

should be struct PRTContext;

[mistafunk]

done

[jonathan-meier]

It should be std::forward<ARGS>(valueFuncArgs)..., ARGS should be expanded with the outer expansion, since std::forward only takes a single template parameter. This only compiled because getCachedValue is so far only used with a single value for valueFuncArgs.

[mistafunk]

oopsie, obviously wrong... fixed.

[jonathan-meier]

Thinking a bit further about this function, two more optimization opportunities come to mind:

• perfect forwarding of the value returned by valueFunc:

  auto value = valueFunc(std::forward<ARGS>(valueFuncArgs)...);
  p = cache.emplace(key, value).first;
  

  the two lines above should simply be the more readable version of:

  p = cache.emplace(key, valueFunc(std::forward<ARGS>(valueFuncArgs)...)).first;
  

  but unfortunately, they're not, because they make an lvalue out of an rvalue. The equivalent would be:

  auto&& value = valueFunc(std::forward<ARGS>(valueFuncArgs)...);
  p = cache.emplace(key, std::forward<decltype(value)>(value)).first;
  

• perfect forwarding of key:
  Unfortunately, we need to rely on SFINAE for the type constraint on key to be able to use a forwarding reference.

Full code:

template <typename M, typename K, typename F, typename... ARGS,
		typename = typename std::enable_if_t<std::is_convertible<typename std::decay_t<K>, typename M::key_type>::value>>
auto getCachedValue(M& cache, K&& key, F valueFunc, ARGS&&... valueFuncArgs) {
	auto p = cache.find(key);
	if (p == cache.end()) {
		auto&& value = valueFunc(std::forward<ARGS>(valueFuncArgs)...);
		p = cache.emplace(std::forward<K>(key), std::forward<decltype(value)>(value)).first;
	}
	return p->second;
}

you just have to admire the beauty of generic C++ code 😃

[mistafunk]

good stuff, done