hi guys
i am in trouble with add picking object in a JOGL project.
i know that this could be done with pick buffer.. but i can't find examples
anyone?
In general, as you are probably aware, JOGL code translates directly from any other OpenGL examples you might see on the web.
GL_SELECT based picking seems to be very much out of favour these days; deprecated in the spec and poorly implemented by drivers.
Alternatives you can use are:
Rendering each object with a unique color (and all lighting / fog etc disabled) so you can determine which object the mouse is over via glReadPixels. (Clearing buffers after the picking stage so that you can then render your normal graphics). This approach is explained by the top rated answer in OpenGL GL_SELECT or manual collision detection? for example.
Ray-casting into your geometry (see the selection FAQ link below). This also means that you don't have to have an active gl context in the thread you call the code from, fwiw.
I've used both of these methods in the same application, currently having good results with the latter, but since most of the objects in that application are spheres it is a lot cheaper than it might be with arbitrary models.
http://www.opengl.org/resources/faq/technical/selection.htm
Related
This is not a joke. and I want a tutorial.
I want to make a 3D (node editor / programming language / graph editor) like this picture:
How can I do that?
These are just some thoughts on the matter, I think some planning will be required.
I'm unaware of any tutorials explaining how to build node editors, but since so many node editors exist, perhaps your best source for inspiration can be other people's codebases.
I think you can look at prior art:
https://architecture.mit.edu/computation/project/visual-programming-three-dimensions-visual-representations-computational-mental
Also, I think you can plan it like this:
figure out what it will look like (maybe you can make a mockup on blender first)
think about what kind of interactions will be allowed, how will the mouse work?
Consider using an existing 3d framework like openframeworks or unity
design a command palette or list of keyboard shortcuts of things that will be required
study existing 2d note editors, consider evaluating the work of John Paul Morrison (Flow Based Programming) and things like NoFlo or PyFlow among many others, you can study the ones that have actual users like the Unreal Node Editor, or more recently I think Unity also has one.
design an execution engine (how will the code actually run, input ports, output ports, etc).
consider the format that you'll use for saving/loading the networks, is it sqlite? json? will you need to store the coordinates and perhaps the dimensions of the nodes, and the connections between the nodes?
if a new node is to be located, where will it be put? do you need to indicate an arbitrary point in 3d space, or is it better to have the new node positions to be relative to existing objects?
component property editors may be important, each node will probably have it's own set of properties, will each node be custom, with a custom ui for editing? or will there be a general property editor for all the nodes? these decisions should be made.
custom node properties can be used to make the ui easier for the user, however
the global property editor will allow you to create many components relatively inexpensively.
what operations need to be supported? do you need auto-layouting algorithms, like graphviz's dot?
will the runtime allow for step by step execution? node statistics? real time visualization?
consider who is your target market for this tool, and why this tool will be useful outside the existing tools, is it music artists using the next vvvvv ? or is it graphic artists making the next shader? will be useful for web development? or for a specific niche?
I hope you'll find these thoughts and ideas useful in your process, and I look forward to the things you will build.
I just want to get the main idea/principle of openFOAM and how you create a simulation, please let me know where I go wrong,
So basically you have a object that interacts with gas or liquid and you want to simulate this, so you create model of the object, mesh it, specify where the gas will flow in and out and what are the walls, and set the other correct parameters and then run the program (with the approprate time step etc)?
OpenFOAM is an open source C++ library which implements the finite volume method (FVM), which is widely used in CFD.
What you have explained is a vague understanding of some of the applications of CFD. Those things you specified might not always be the case (i.e. the fluid might not necessarily be (a) gas and so on.
The main stages of a CFD problem are: making the geometry - mesh generation - preprocess - solving - postprocess.
There might be more stages added depending on the resolution and other specifics of the case.
Now OpenFoam is an open source (free for all) tool which is in C++ and helps solve the CFD problems. If the problem is simple and routine, and you have access to a commercial solver such as ANSYS fluent, then you can use that since it is easier and much less work if the problem is not specific. However, if the problem is specific and there are customized criteria OpenFoam is a nice tool.
It is written in C++ thus it is object oriented and also there are many many different solvers already written and available to use, so you will not have to write all the schemes and everything on your own from scratch.
However, my main advice to you is to read more about CFD to have a clear understanding, there are tens of good books avaiable.
I am in the process of coding a level design tool in Qt with OpenGL (for a relevant example see Valve's Hammer, as Source games are what I'm primarily designing this for) and have currently written a few classes to represent 3D objects (vertices, edges, faces). I plan to implement an "object" class which ties the three together, keeps track of its own vertices, etc.
After having read up on rendering polygons on http://open.gl, I have a couple of questions regarding the most efficient way to render the content. Bear in mind that this is a level editor, so I am anticipating needing to render a large number of objects with arbitrary shapes and numbers of vertices/faces.
Edit: Updated to be less broad.
At what point would be the best point to create the VBO? The Qt OpenGL example creates a VBO when a viewport is initialized, but I'd expect it to be inefficient to create a close for each viewport.
Regarding the submitted answer, would it be a sensible idea to create one VBO for geometry, another for mesh models, etc? What happens if/when a VBO overflows?
VBOs should be re-/initialized whenever there's a need for it. Consider VBOs as memory pools. So you'd not allocate one VBO per object, but group similar objects into a single VBO. When you run out of space in one VBO you allocate a another one.
Today's GPUs are optimized for rendering indexed triangles. So GL_TRIANGLES will suffice in 90% of all cases.
Frankly modern OpenGL implementations completely ignore the buffer object access mode. So many programs did made ill use of that parameter, that it became more efficient to profile the usage pattern and adjust driver behavior toward that. However it's still a good idea to use the right mode. And in your case it's GL_STATIC_DRAW.
I am required to do some 3-D application and planning to chose some library for the same. I have previous experience with Qt-qml.
I read about OpenGl and found that it must be used basically when you one has very low level drawing requirements.
I also found that there is something called QtOpenGl.
Q1. Is QtOpenGl any less powerfull that OpenGl because it just just provide a wrapper over some OpenGl functionality? or it as good as using OpenGl with an advantage of working at higher level of abstraction ?
Q2. I also found there is something called Qt-3D and Qt-Quick3D. I ran some sample examples and found it easy to use because of my previous experience with qml.
Can someone share experience how powerful it is compared to OpenGl itself?
My basic question is how low the drawing requirements should be that I should use OpenGl rather than some higher abstraction like QtOpenGl ?
Q1: The Qt OpenGL module is not exactly a wrapper aroung OpenGL. It is a wrapper around GLX, WGL, or AGL. You can anyway render with QPainter using the Qt OpenGL engine. Look to the documentation to see if it is sufficiently low for you. Only 2D anyway.
Q2: Qt3D will be part of Qt5 as far as I know. It depends on what you want to do. If you want to implement 3D games it is probably quite risky. Only you know if it is sufficient for your needs.
I am currently considering writing a small game. It is essentially a map where you can zoom out and in, and in certain places click on info boxes where, at some point, I hope to integrate minigames. Granted, game might be overstating it. Think of it as an interactive map. The theme is how mathematics can be applied in peoples every day life to raise awareness on the usefullness of mathematics.
The question is how I as fast as possible can make a reasonable prototype. If I recieve enough positive response on this I might try to code "the real thing" and use the prototype to obtain funding.
However, I am at a crossroad. I want something to work rather fast and have some C++ experience coding optimization problems, mainly in c-style. I am not convienced, though, that coding it in C++ is the fast way to obtain a prototype. Though I have some experience coding in C++, but have no experience in coding any sort of GUI.
As I see it there is a number of possibilites:
C++, possibly using some library, such as boost or ???.
Start out purely webbased, using e.g. HTML 5 and java.
Python
C#/.NET
Others, such as?
I have to admit I have little experience with anything besides C++ and the STL.
So my question to this wonderful forum is basically, is there a language that provides a significant advantage? Also, any additional insight or comments is more than welcome!
Python is a simpler language than C++, and for prototyping it will help you focus on the task at hand. You can use Pygame, a game library built on the excellent cross-platform SDL library. It provides 2D graphics, input, and audio mixing features. SDL is mainly a C library (and thus compatible with C++), and there are a number of very useful libraries that integrate with it:
SDL_image for loading images in various formats
SDL_ttf for rendering text using TrueType fonts
SDL_mixer for audio mixing
SDL_net for networking
SDL_gfx for graphics drawing primitives
So if you prototype in Python using Pygame, there is a reasonable chance you’ll be able to port what you make over to C++ with minimal hassle, if and when you choose to do so.
Possible options:
Go with what you know the best. Anything else will require a learning curve, which may be weeks to months long. If you're willing to take that road in order to make your prototype, then there are some really great tools available.
BlitzBasic is a good way to go, and is basically designed to be for games
I've done little games in Java using Slick2D - but you'll need good grounding in object-oriented coding to work effectively in Java. If you've got that from C++, then you can see a tech demo I built in Slick2D called Pedestrians. It's open source, and has demo videos here.
You might also ask your question on https://gamedev.stackexchange.com/ - a Q/A site dedicated to game programming