# OpenGL Time to write rendering engine from scratch

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bigneil    49
I have a new assignment where my boss wants me to write the complete source code for a simple rendering engine that can load and render standard file formats like OBJ (at least one format) but it needs to be written from scratch.

It's been a while since I wrote one from the ground up (15 years or so), in fact it seems hardly anything in graphics is written from scratch these days. The pay is great so I don't have a problem doing it, but am at a loss for an estimate and wanted to get a consensus from those with experience.

How long would you estimate it would take to write an OpenGL program that can load say OBJ files and render models without fancy shaders?

Also, what file format is most straightforward to load and render?

Thanks in advance. Edited by bigneil

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Kaptein    2224
I agree, it will take time to learn all the stuff necessary to write a serious and correct viewer that works according to the endless amount of specifications you'll need to know.
But, feel free to ask anything in here if you run into any problems..
I would start with GLFW for the openGL window, and go from there, as it is multiplatform (win, linux, mac), and handles the window, inputs and swapping (including vsync) for you.
Unless you also have to do that by hand

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Krohm    5030
I'd be extremely careful as the goal is not clearly defined. I use AssImp for the loading yet I'd find hard to take less than 5 working days. But perhaps my definition of "without fancy shaders" is different from yours. Edited by Krohm

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Tordin    625
As L. Spiro say, it´s personal. And if you dont have any experiance in coding with either Dx or GL it will probably take a while to figure out how things work.

Use Assimp, it´s easy, it´s good, it´s fast and honestly saved me alot of work and time. it allso supports a ton of formats.
estimate to one month. thats a good start amount, you have room to develop, and to fix bugs, and to correct or rewrite stuff if you are forced to.

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bigneil    49
Generally unsure of myself? 15 years rusty?

And it would take Spiro 2 days and it would take me 2 months?

Who is Spiro trying to impress? A group of anonymous computer nerds?

FYI I've programmed OpenGL every day for the past 15 years, and patented my own rendering system in the process. My own product already served as a rapid prototyping tool and I solved their actual problem in my first few hours.

It just happens they want the source code (a license of which I sell for $250K). I'm just pointing out that people don't usually write rendering engines from scratch anymore (the one I wrote in 1997 is still working fine thank you), and if someone tells you they can write a rendering engine from scratch in 2 days they are lying. #### Share this post ##### Link to post ##### Share on other sites Bacterius 13165 [quote name='bigneil' timestamp='1351866936' post='4996539'] I'm just pointing out that people don't usually write rendering engines from scratch anymore (the one I wrote in 1997 is still working fine thank you), and if someone tells you they can write a rendering engine from scratch in 2 days they are lying. [/quote] Your stated requirements were vague, basically "parse an OBJ model and display it to the screen with a basic shader". This as stated can be done very quickly, in a matter of days if you work hard at it. Of course, adding requirements and features will increase the time accordingly, but you did not mention these in your question, they were therefore not mentioned in the answer. [img]http://public.gamedev.net//public/style_emoticons/default/mellow.png[/img] Your two posts are somewhat inconsistent with each other, is there something you're not telling us? Edited by Bacterius #### Share this post ##### Link to post ##### Share on other sites Tordin 625 [quote name='bigneil' timestamp='1351866936' post='4996539'] Generally unsure of myself? 15 years rusty? And it would take Spiro 2 days and it would take me 2 months? Who is Spiro trying to impress? A group of anonymous computer nerds? FYI I've programmed OpenGL every day for the past 15 years, and patented my own rendering system in the process. My own product already served as a rapid prototyping tool and I solved their actual problem in my first few hours. It just happens they want the source code (a license of which I sell for$250K).

I'm just pointing out that people don't usually write rendering engines from scratch anymore (the one I wrote in 1997 is still working fine thank you), and if someone tells you they can write a rendering engine from scratch in 2 days they are lying.
[/quote]

- "It's been a while since I wrote one from the ground up (15 years or so), in fact it seems hardly anything in graphics is written from scratch these days. The pay is great so I don't have a problem doing it, but am at a loss for an estimate and wanted to get a consensus from those with experience."

Here you state it was a long time you wrote it from the ground and up. (by just sligtly reading, this is easy read as "i havent done it in 15 years" )
And to add the title states, "Time to write rendering engine from the scratch", this adds more to the idea that you havent done it in a while.

- "How long would you estimate it would take to write an OpenGL program that can load say OBJ files and render models without fancy shaders?"
This gets me to think, you are asking for advice out from experienced developers to get some estimate on how long this task would take, because you sound like a rookie on the sentence befor. ( you might not be a rookie )

- "Who is Spiro trying to impress? A group of anonymous computer nerds?"
I belive none, in fact, i think you got this on the wrong hand. as we got your "Question" on the wrong hand aswell.
If you have been writing OpenGL for 15 years, the you would be pretty sure of how long it would take you to develop that stuff, due to the fact that you know the problems, the issues, and the solutions for it. and you would allso give an planned approach and estimate upon that. Edited by Tordin

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L. Spiro    25622
[quote name='bigneil' timestamp='1351866936' post='4996539']
it would take Spiro 2 days and it would take me 2 months?
[/quote]
I don’t know. How long [i]would[/i] it take you?
That is what we are trying to determine.

[quote name='bigneil' timestamp='1351866936' post='4996539']
I wwebsite as on the internet
[/quote]
You obviously know more about yourself than any of us, but put that aside for a moment and read your post and then my reply.

If you can’t handle the answer, don’t ask the question. If you do ask the question, you should provide all of the necessary information. When estimating how long it would take you to complete a task in OpenGL, it would be a good idea to mention any experience you have in OpenGL up-front.

It’s generally assumed that if you come here to ask a question, you [i]want[/i] to find people who are more experienced than yourself so you can get help from them.
If this wasn’t your thinking, then what was? Did you hope to find a bunch of people saying, “It would take me 3 weeks,” so that you could say to yourself, “What a loser, I am so much better than him or her”?

L. Spiro Edited by L. Spiro

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mhagain    13430
Just to elaborate on L Spiro's first answer (which is quite correct, by the way), your first task is to create a window, get a basic message loop running, and write a basic render function that just clears the screen and does a swap buffers.

Depending on how familiar you are with that process, depending on how many platforms you want to support, depending on whether you need to write platform-native code or are allowed to (or are allowing yourself to) use any helper frameworks, depending on whether you need to learn a new platform from scratch, this could take anything from minutes to weeks or even longer.

It really is that open-ended and you've supplied insufficient info in your original question to allow anyone to correctly gauge your level of knowledge or ability here. 15 years experience in OpenGL means squat when it comes to having to learn the intricacies and pitfalls of a new platform from scratch - even someone like John Carmack still makes basic mistakes on the platform he's most familiar with, so please don't try to imagine that you won't.

From there you need to load and parse a model format. Go back and re-read your opening question again; does it read like the kind of question asked by someone who is familiar with a good variety model formats? Now, .obj is a plain text format so you've got some nasty parsing and conversion ahead of you; have you given any indication that you're aware of this? Do you see now why your open-ended question could elicit an open-ended response?

Back to .obj; like I said, there is some nasty parsing and conversion to be done, but for the most part this is already a solved problem. But you say "from scratch", so for you you may first need to learn the format, then write a loader, then decide how you're going to draw it (as this will greatly influence your loader). Are you going to use immediate mode? Vertex arrays? VBOs? How much experience do you have in these? It's possible to spend 15 years doing OpenGL without ever having gotten within spitting distance of a VBO (especially if the codebase you're most familiar with dates back to 1997) so do you need to learn VBOs from scratch too? You may need to if "it must run fast" is part of your specification (which you haven't clarified).

Again, do you see how open-ended this is?

From there, and since you mention that you're not using shaders (or are you just not using fancy shaders?) I'm going to assume that you're back in familiar territory and can form your own estimate - you're the person in the best position to do that. But do note that I said "assume" here. And also note that I left out anything relating to whether or not the model needs to animate.

As for the simplest model format to load, that would be a proprietary format that you design yourself and that is set up so that you can just read the data directly into the most appropriate in-memory format for rendering from. It could be as basic as a single fread followed by a single glBufferData call - can't get much simpler than that. As a general rule, the more open a model format is the more complex it is as it needs to be able to support the needs of multiple programs doing different types of rendering, but it can virtually always be guaranteed to take the flexibility side of the tradeoff.

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bigneil    49
I'm not sure how "It's been a while since I wrote (a rendering engine) from the ground up" was interpreted as "it's been a while since I programmed graphics (in any capacity)", or who wouldn't take "you sound rusty and unsure of yourself" as less than insulting, but I appreciate the advice. Thanks everyone.

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bigneil    49
Because I was just tasked with writing a rendering engine from scratch I wanted to get a consensus on what people who have written rendering engines more recently thought.

In the end I decided to whittle down my own code since it works perfectly (and recompiles in 6 seconds to all you A-holes who write programs that take 2 hours to compile (see Electronic Arts).

But man, I forgot what a bunch of d*uche b*gs are on this site. Members here (what an appropriate term) pride themselves on their blog rating here and you'll never find a site more likely to neg you for one post that doesn't stroke their ego. Try saying you don't like Goto for example - they'll neg you all the way to negative 1000.

Most of the people here with high ratings don't actually have computer science jobs (or formal experience) which is why they have so much time (and why they are so bitter).

Worse, they provide best-case scenario estimates - an enormous disservice to themselves, coworkers and the industry. A wise man once said "The more I know the less I understand" - and members here understand everything.

If you've worked in the industry you know you'll never find smarter people who are willing to do exactly what they are told (by their boss, the FDA and the TSA) - Developers in a crisis will (according to Meyer Briggs) "go with what the group does".

Oh well, I'd rather be making \$90 an hour programming OpenGL for my own business than to have a high db rating, but if you make less be sure to neg me.

Anytime you do something worthwhile you're going to offend someone.

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popsoftheyear    2194
Whoa whoa whoa
[quote name='L. Spiro' timestamp='1351813476' post='4996360']
[b]If[/b]...
[b]If[/b]...
[b]If[/b]...
[b]If[/b] you are generally unsure of yourself (and it [b]sounds[/b] as though you are), I would say you should give yourself no less than a month, maybe up to 2.

[b]Because of the wide range of skills and experiences, I am not sure how helpful any of our answers would be[/b].
[/quote]
1) I don't believe LS was tearing you down or diminishing your character. And I'm pretty sure the way you reacted to LS and similar answers set this thread downhill. Clarification on your part probably would have went a long way.
2) [i]Plenty[/i] of people here don't like goto (unless absolutely positively necessary, which it usually isn't).
3) I don't believe you can get a negative rating - perhaps I am wrong about that one though.

Please try to reconsider your perspective on all this - it's not what you think it is.

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Bacterius    13165
[quote name='achild' timestamp='1352238672' post='4998210']
3) I don't believe you can get a negative rating - perhaps I am wrong about that one though.
[/quote]
No you actually can. Lowest I've seen so far is -350 or so. Not that ratings matter that much anyway. I've come to the conclusion that the thread creator is a troll, and you know what they say about trolls. Edited by Bacterius

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mhagain    13430
I can only second L Spiro here.

You ask a question, which it must be assumed was well-intentioned and in good faith.
You get some answers that also read as well-intentioned and in good faith.

From there it seems that you didn't like the answers you got and the resulting conflagration borders on thermonuclear war. Not good.

I'm not saying that you're obliged to like the answers, but there is such a thing as basic manners - people have freely and willingly given of their own time here.

One can only answer a question based on the information contained in that question; if the answers recieved are believed to be inadequate or otherwise lacking then there is obviously a communication deficit of some kind to be addressed. Strikes me that it would have been far more productive to address that deficit than to engage in flaming out.

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Caffeware    151
[img]http://public.gamedev.net//public/style_emoticons/default/huh.png[/img]

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bigneil    49
[quote name='Caffeware' timestamp='1352320584' post='4998571']
[img]http://public.gamedev.net//public/style_emoticons/default/huh.png[/img]
[/quote]

Excellent Caffeware - I downloaded it and it ran instantly - this is how all software should be written!

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bigneil    49
Yes! I almost achieved my negative rating!

This shows what a farce it is.

When you're a 20 year veteran of the 3D graphics industry and already worked on Madden Football, Far Cry, Doom, Descent and other games, the rating system doesn't disprove you, you disprove the rating system. Edited by bigneil

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bigneil    49
"Strikes me that it would have been far more productive to address that deficit than to engage in flaming out."

It's the forum that flames out. I was once a member for years and had a rating of 400 or so, then when I said I didn't like Goto my rating went all the way to -400 - OVER ONE THREAD. Edited by bigneil

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I really do not get why you're reacting this agressively to people's reactions, there was no need for any agression, nobody tried to flame you or attack you in any way whatsoever. You got some valid answers to your question, there may have been some misunderstandings and miscommunications but there's no reason to suddenly react the way you did.
You claim to be an industry veteran of 20 years, if that's true you might want to think about acting somewhat more like an adult then in this situation instead of starting to flame and trying to profile yourself as superior to everyone else because of the projects you have done or (of all things) the compile times you get.

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L. Spiro    25622
[quote name='bigneil' timestamp='1352410597' post='4999033']
When you're a 20 year veteran of the 3D graphics industry and already worked on Madden Football, Far Cry, Doom, Descent and other games, the rating system doesn't disprove you, you disprove the rating system.
[/quote]
I am really getting tired of you and your inferiority complex. You asked a question hoping to find people with more experience than you on a given subject.
I answered because that subject is exactly down my ally. When I go to work, I make a game engine (unless I am going to my other job that is). When I get home, I make a game engine.

[i]Game[/i] engines aren’t [i]rendering[/i] engines, but it just so happens that my current task at work is the rendering part, and on my own engine I am currently working on the rendering part.
[quote name='bigneil' timestamp='1352410597' post='4999033']
Because I was just tasked with writing a rendering engine from scratch I wanted to get a consensus on what people who have written rendering engines more recently thought.
[/quote]
And I am exactly the person you wanted to answer this question. [i]I am writing a damned book about rendering/loading graphics files/etc. as we speak.[/i]

Suddenly you are offended that someone is better than you at this task, yet why wouldn’t I be? It’s what I do all day every day—whatever you do all day every day probably makes you better at that than I am.
So your inferiority complex kicks in and you have to make up for it in other ways—salary, past projects, status, etc.
I have been extremely kind up to this point, having passed up numerous chances to put you in your place, but here is the deal: [i]You don’t impress me.[/i]
There are people here who do, but you will never be one of them. They impress due to their skills and professionalism. Your salary, past projects, and status as a business owner are [b]not[/b] impressive. Once again I am leaving it at that instead of taking you down a few notches, although you do deserve to be put in your place. I can at least say that based on your salary, past projects, and status as a business owner, you have no place to brag, so listing these things as an attempt to make up for your shortcomings in skill only make you out as someone that much more desperate to have lived a better life. Just stop trying to make yourself more than you are, because I can promise you that no respectable person I have ever met has made the kinds of posts you have made, trying to prove themselves to some other random person online. Each time you do so just makes you much less of an impressive person and much more like the kind of person who wishes he or she was more than he or she actually is.

[i]You[/i] are what’s bringing this site’s quality down.
You only come here to flame and brag about yourself, and this topic serves absolutely no purpose to anyone who stumbles upon it in the future. It starts with a very vague question and quickly becomes a 1-man flame-war. Then you make it clear that your goal is only to get a negative reputation (I still haven’t touched your reputation, by the way).
I am not a moderator here, but it is [i]obvious[/i] that if you don’t take a contributory tone starting from your very next post, [i]you will be banned[/i].

L. Spiro Edited by L. Spiro

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mhagain    13430
At this point I need to chime in about reputation.

Reputation is NOT there to stroke anyone's ego. Any member of this site with sufficiently high reputation is most definitely NOT getting an internet hard-on (pardon the choice of phrase, couldn't think of a better way of putting it) from it, because they understand the purpose of the system.

The reason for reputation is to act as a service to the community. People can identify the good answers to questions, the ones that are most likely to be the right answer or to at least shove them in the right direction.

A good, fully functioning member will [i]welcome[/i] negative reputation as much as they welcome positive reputation, because they will see negative reputation as something that puts their own previously held assumptions to the test. Because they understand that no matter how much one is experienced, no matter how much one knows, learning is a continuous process.

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As a slight topic digression, what is the state / benefits to your engine Spiro? I'm always interested in hearing what goes on
As a member who frequents another forum devoted to a specific software, I hope I can provide something in the nature of an opinion.
I myself do not work in rendering engines. I have little experience, yet enough to understand that it can become a quickly all-encompassing task.
The issue here is that you failed to address a generic opening. This is the cause of the troubles. If you have a genuine question, ask it again, and perhaps apologise if you feel that you have overreacted. If you feel that this is unfair, then lest this topic be useful to others it should be left. Best of luck to all.

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