The C4 Engine is a comprehensive suite of professional, robustly implemented game programming tools for PS4, PS3, Windows, Mac, and Linux.
I've been working with this engine for almost 2 years and love the code base. You do not need external libraries like stdlib or boost and nothing is hidden, so in the rare case that bugs are encountered, they are found and removed by the engine creator almost immediately.
Great engine and fast service in the forums.
I've only been working with the C4 Engine for a while now, but I've had enough experience with other game engines, to tell you what things made C4 the obvious choice for me.
Integrity - Refreshing to see an engine tell it straight about needing source code access. Anyone saying different is telling half truths. Period.
Cost - Reasonable price, forever, no upgrade costs, no royalties to further constrain your budget! Depending on your license type you can even have small features added or problems solved for your own needs. For simple problems Eric or the community will normally help over the forums.
Support - Eric is terrific, I can't say this enough, timely responses to questions/problems, new features and bug fixes regularly worked on. A professional and mature community offers its support as well.
Architecture - The design, and the clean thoughtful approach taken to implementing all its features makes understanding and working with it an enjoyable experience.
Features - Regularly being updated, the roadmap shows the few features missing that contenders offer (SSAO, HDR) are being implemented, plus it offers a some things you will only find in C4 like Transvoxel Terrain, Horizon Mapping for example. Being able to request small feature additions, and have a part in discussing with the community and Eric himself the importance and implementation of features shouldn't be under-stated.
Performance - After some stress testing, I'm extremely impressed how far I can push it. It's well designed to let me push the envelope in an organized way.
Modular - Full source and a clean design lets me choose my priorities and extend as needed.
Plugins - Being able to add plug in new features as opposed to replacing parts of the engine allows you keep your game updated to the latest version of the engine without needing to manually merge them.
Extremely happy with my choice of the C4 Engine. If you serious about making a game, take a serious look at C4, you'll be happy you did!
I have used several engines, and C4 has by far the best design I have ever seen. It's really a pleasure to work with this engine after dealing with all the hidden shortcomings of engines like Unity, and it even costs less. Plus there are frequent updates and the community is very professional.
In between the long list of robust features, tools and the dedicated thorough support by Terathon and its vibrant community, the C4 engine is a premium package at a bargained price. The under pronounced fact that a license is entitled to free updates for LIFE is monumentally valuable. I purchased the engine in '08 as an investment, and by golly was it a good one.
Code is polished clean. If you're interesting in learning more about C++ and OOP design, the cost of the engine is easily worth what you'd learn in study, since at least Standard and Professional licensees are granted full source code access. Bugs are rare, and once discovered are timely fixed. In my years of community engagement, I haven't seen a single bug go unpatched longer than just a few days.
Support is phenomenal, all around. The tight crew over at the forums are always eager to help, and range in experience from "moddlings" all the way over to seasoned professionals. Again, the cost of the license alone is worth the value gained from access to the private Licencee forum.
The features work, AS ADVERTISED. If you dislike how something functions, open discussion is encouraged at the forums, where Terathon actively engages. Past peer-review, licensees can submit feature requests and I've personally had a handful of requests implemented at no additional cost to myself.
Terathon is a good hearted, fair playing company. I've never seen them conduct unethically and are always upfront and honest with their customers.
The only thing I've noticed that jives people off is the lack of embedded graphical spazz. The waiting is nearly over. 3.0 is currently in development and contains a number of advanced and modern graphical effects.
The C4 Engine has become one of the most impressive engines out there while still maintaining a low price tag and providing updates free of charge. Not only are new features constantly being added, but the community is one of the most helpful I've ever seen.
One of the key things that makes the C4 Engine stand out is that the sole developer of the engine personally responds to all questions through the forums and provides the highest quality of support possible. Not only is he extremely knowledgeable, but he is dedicated to both the engine and it's licensees and goes out of his way to ensure that your game succeeds.
I can't say enough good things about this engine. The community is very supportive and active. The engine is in constant development and the quality of the engine code is unsurpassed (for instance I have never seen such short build times for a project of this size).
Coming from Unity the world editor can be a bit intimidating at first but having full access to the engine, rather than the black-box Unity is, is invaluable.
I do recommend reading the two published books about the engine to get started quickly.