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sion5

OpenGL Software Rendering

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sion5    100
Hi people, I have been given the task of developing my own software renderer which must have a custom-built maths library to include and demonstrate all basic vector operations, matrix manipulation and perspective transformations. NB. The OpenGL and GLut libraries may only be used to open up a graphics window and to draw single points, for example GL_POINTS. I have Vectors and Matricies implemented as fully functional data types with overloaded operators, copy constructors and accessors. They support add, subtract, scalar divide and multiply, cross and dot products, transpose etc. I can succesfully apply rotations and transpositions to points and using OpenGL's gluOrtho2d() display the results. But when I try to apply my worldView matrix (orthographic) to the points the display is blank :-s The .h and .cpp's can be obtained from the address below: http://www.mediafire.com/?sharekey=92f8e0beba89b27491b20cc0d07ba4d2877a2105c2c5a22c The problematic code is in the Render.cpp draw() function, along with 1 line in main() in the main.cpp. The draw function works as follows: 1. Recieve a vector<Vector3> vertices; 2. Apply currentMatrix (holds transformations) to modelView matrix 3. Apply modelView matrix to vertices, store in an intermediate array 4. apply worldView matrix (orthographic) to the intermediate array 5. use GL_POINTS to draw intermediate array The matrix i have implemented for othographic view is in the matrix4.cpp and was taken from the opengl redbook Any help with this would be much appreciated :-D HAPPY HOLIDAYS ALL

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sion5    100
Maybe people could send me in the right direction with links? I have done forum searches but I cant get past this problem that i have :-(

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C0D1F1ED    452
No, I won't fix your computer.

Seriously now, you're not asking the right questions. You can't expect people to make your homework or do your job. You have to show that you've really tried hard, analyzed the problem thoroughly, and searched for answers on your own.

Your problem looks like a real 'pencil and paper' problem to me. That is, take a pencil and some paper, and do the math. Then run your application with the debugger and check that every variable you calculated on paper corresponds with the value your program produces.

If that doesn't lead you straight to the problem, feel free to ask a specific question. But don't just say: "Here, fix this"!

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daviangel    604
I own 2 books that I remember off the top of my head that covers this in detail and would help one of them being Lamothe's "Tricks of the 3D game programming gurus" the other one being "3D graphics programming games and beyoned" by Savchenko.
See if you can get a copy of those in your library and check them out.

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sion5    100
C0D1F1ED - I have not asked you to do anything except point me in the right direction, I have read a million books but cant solve the problem and unfortunately my lecturers are unavailable because of the holiday period, the forums where my last resort.

"Any help with this would be much appreciated"

Definition of help: give help or assistance; be of service;

Nowhere there does it say "will you do this for me"

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cbenoi1    484
> I have not asked you to do anything except point me in the right direction

That means getting the files, reading the code, and if nothing obvious pops up, compile and debug. I did the first two steps and haven't found anything obviously suspicious. But I'm NOT going to break out the debugger. That's YOUR homework, not mine.

> But when I try to apply my worldView matrix (orthographic)
> to the points the display is blank :-s

You are debugging both your SW rasterizer and OpenGL commands at the same time. I suggest you use a frame buffer instead of drawing points immediately to a window. You can examine the frame buffer's content at any moment, or dump it to a file for further examination. Once you have validated the SW path, you can always replace the piece of code that draw points with an OpenGL version and make sure you get the same results.

-cb

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sion5    100
Ok, well my appologies then I have misunderstood the purpose of these forums. I was hoping that it would be an obvious problem that I had overlooked and was easy to find to the trained eye.

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C0D1F1ED    452
Quote:
Original post by sion5
I have not asked you to do anything except point me in the right direction...

Sure, you didn't ask it directly. But you did dump your code here in the hopes that someone will dig though it and pinpoint the problem and either tell you the solution or "guide you in the right direction". You have to realize that this is a lot of work, and telling you the solution or guiding you takes equal effort since the bulk of the task is in locating the exact issue. So intentional or not, you did ask for us indirectly to fix your code.
Quote:
I have read a million books but cant solve the problem and unfortunately my lecturers are unavailable because of the holiday period, the forums where my last resort.

Reading more books will not help one bit. This is a debugging problem. Something for which you need to roll up your sleeves. And I believe that's the whole point of your assignment. To learn some skills through hard work.

Now, if you were seriously stuck and pinpointed the problem yourself and had already tried everything to come up with a solution and showed that to us, we would be more than happy to try to tell you what you're doing wrong and which approach might be more succesful.

And I believe that's exactly what I'm already trying to do here. See, although this thread's title says "Software Rendering", it has practically nothing to do with it. There are a million ways to implement a software renderer (and each of the million books you read probably has a different one). If you understand the math and you have an implementation that 'should' work but doesn't, this is nothing more than a debugging problem.

And it's one that asks for a pencil and paper approach. Take some input data that you know should end up at a certain location on screen. Make it as simple as possible, like a cube that's half the size of your screen width. Set all the matrices you don't need to the identity matrix. It's just you against the orthographic projection matrix then. Calculate on paper that it works as intended. Then check whether your code does the exact same calculations and outputs that on the screen.

Either this will pinpoint the issue, or it will show that you don't fully understand the math yet. I doubt it's the latter since you read a million books and you dumped the code on us not the math, but still, if you do need a hand in the math area we'll be more than happy to help if you have any specific questions.
Quote:
Ok, well my appologies then I have misunderstood the purpose of these forums. I was hoping that it would be an obvious problem that I had overlooked and was easy to find to the trained eye.

Don't sweat it. ;) Everyone makes that mistake at least once. You just have to understand that the "trained eyes" on this forum are payed to do tedious debugging during their daytime job. It's even more annoying when looking at other people's code. They're happy to help you out with any actual technical problem though, the exciting bit. Debugging is just something each has to do himself, and you can only learn this skill through practice and by taking generic advice (there is no single recipe for successful debugging)...

Good luck!

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realkiran    100
Quote:
Original post by C0D1F1ED
Everyone makes that mistake at least once. You just have to understand that the "trained eyes" on this forum are payed to do tedious debugging during their daytime job. It's even more annoying when looking at other people's code. They're happy to help you out with any actual technical problem though, the exciting bit. Debugging is just something each has to do himself, and you can only learn this skill through practice and by taking generic advice (there is no single recipe for successful debugging)...


Originally I disagreed with C0D1F1ED but then I downloaded your code and completely lost interest. There's just too much to go through, and too many places an error could be present. I don't see a glaring error but I only spent 5 minutes looking.

I suggest you check your matrices against some reference... perhaps matrices produced by opengl functions? Piece by piece take something that definitely works and compare it against your own code. If you find a discrepency and you legitimately can't figure out why... post the relavent code here and I'm sure people will be able to explain it to you.

-Kiran

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kittycat768    102
sion5, it might help more if you found the section of your code that actually attempts to do what you are asking about and put it in your post, otherwise you are a grinch magnet.

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