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.
I went through two other engines before I settled for C4, Irrlicht and Ogre. I wasn't necessarily looking for a free engine but at the time (7 resp. 4 years ago) there wasn't much choice.
C4 simply works and if something doesnt work, it's a good chance it's you doing something wrong and not the engine. In that case you will almost always get help in the user forums, the community is very helpful and the developer also answer questions regularly there, it's one of the features that really sets this engine above the others.
That said, I reversed my original rating from 10 to 4. I save myself the bother of repeating everything that Argoon has said in his review, because he sums up my own criticism after over a year of C4 usage very well.
C4 is very good render engine, stable and fast. However the tools lack usability and force you to write anything you do within the C4 framework. You can not write a stand alone converter tool for instance because it has to be called from within the C4 main screen and you have to have a complete directory layout just for one tool. This means in the end that you have to keep and maintain several copies of the data directory hierarchy.
Writing an application outside the given framework is possible but with a lot of woe. You wont be able to write standa alone tools for instance, only tools that use the engine GUI and start from within the engine main frame. Also dont expect any help when you do. Help is provided in the forums, but you have to use the engine the way it was intended by the developer or you're on your own.
There is not much documentation on the library,in order to do anything beyond the obvious you have to go to the forum and ask for help and hope the developer is in the mood to help. He may or may not. The engine contains absolutely no source code comments and the included header comments often just repeat the function name and parameters and otherwise leave you in the dark.
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.