hey
i am creating a pool table simulator in opengl written in c++
i have the basic table drawn but now i need to add some pockets
i want the pockets to be a basic curve like a C shape
im not quite sure how to do this
i have experimented with trianglefan but iv had no luck
can anyone help please?
also i must add this is part of a university project therefore i will only be using the core opengl and c++....no other tools
thanks in advance
When I use OpenGL, I usually build the models in something like Blender.
Blender is free and allows export to WaveFront obj - an easy format to read in to your program. Or you can use the simple text WaveFront obj with a little scripted editing will produce a list of vertices that you can use in arrays for vertex buffer objects.
I couldn't imagine trying to build objects for a 3D scene using only discrete values and discrete math like (I think?) you're describing.
Do you have access to glu.lib?
http://en.wikipedia.org/wiki/OpenGL_Utility_Library
http://www.opengl.org/resources/faq/technical/glu.htm
That would easily make cylinders or NURBS curves for the pockets. Sample use of it is here: http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=18
There is also lots of code from the "Graphics Gems" series available - you can dig through the early books for something suitable if GLU isn't an option.
http://www.graphicsgems.org/
Start with a cube and slice off the bottom corners. Refine as necessary.
Related
I'm a newbie in this type of approach to programming since I really doesn't care for hardcore graphics generation. I design, write, run, and study parametrized climate models with python. But, at last, I have encountered myself with a visualization issue.
I was looking for something in Cairo library that allows me to map a linear gradient onto an arbitrary curve (not necessarily a circumference) such that there is a more or less smooth variation of colour (or shade) across my path. Then I have been looking for some pattern and I finally found that maybe mesh gradients in Cairo are the solution.
However, I can't create a new mesh gradient from my python script with cairo.pattern_create_mesh()!
Therefore, my questions are: How I use mesh gradients in Cairo? Is there any other simple way to do what I want with Cairo (I don't know, like a simple mapping from a line segment to a curve via parametrization, I know I ask too much)?
Mesh patterns were added in cairo 1.12 which is the latest release. Thus, most language bindings likely don't support them yet. I don't know anything about the combination of python and cairo and thus don't know any workaround.
I don't know any simple way to simulate what you need with other patterns, sorry. (Although I am not really sure how you want to do your mapping via mesh gradients either...)
Suppose that I have a 3d model with animation in, say, Blender. I need to export this model to some file and then use it in OpenGL app, i.e. without hardcoding animations, but reading them from file. What format is the best solution?
OpenGL doesn't support any format directly, but the classic OBJ file format lines up very well with drawing with vertex arrays. Basically, OBJ lists all vertices independently of the geometry. This way, several objects can share the same points. All kinds of groupings are also possible.
Also, it is one of the earliest formats to support a wide range of spline curves & surfaces, including Bezier, B-Splines & NURBS.
A basic decription can be found here:
http://en.wikipedia.org/wiki/Wavefront_.obj_file
The complete OBJ spec can be found here:
http://www.martinreddy.net/gfx/3d/OBJ.spec
It's not as modern as WebGL, but it's simple, human readable and widely supported.
What format is the best solution?
OpenGL doesn't care about file formats. So feel free to choose whatever suits your needs best. Due to the rise of WebGL I started dumping whole Blender scenes into collections of JSON formated files.
I'm working on an Augmented Reality project that uses multiple markers to get positions for 3D models that I'm planning to overlay. (I'm doing this from scratch using OpenCV and I'm not using ARToolkit or any other off the shelf marker detection libraries).
Environment: Visual C++ 2008, Windows 7, Core2Duo 1GB ram, OpenCV 2.3
I want the 3D models to be manipulated by user so it will turn out to a sort of simulation.
For this I'm planning to use OpenGL. What are your suggestions, recommendations? Can the simulation part be done by using OpenGL itself or will i need to use something like OpenSceneGraph/ODE/Unity 3D/Ogre 3D?
This is for an academic project so better if I can produce more self-coded system rather than using off-the-shelf products.
it would seem that OpenGL is pretty enough for your needs (drawing a model with a specific colour and size).
If you're new to OpenGL, and you are not going to be using it for your future projects, it might be easier to use the old fixed-function pipeline, which already has the lighting and color system ready and doesn't require you to learn how to write shaders.
For your project, you will need a texture where you would copy the image from camera using glTexSubImage2D() which you would in turn draw to background (or you can use glDrawPixels() in case you don't require any scaling). After that, you need to have your model, complete with normals for lighting. Models can be eg. exported from Blender or 3DS Max to ascii format, which is pretty easy to parse. Then you can draw the model. Colors can be changed using glColor3f() before drawing the model (make sure you don't specify different color while drawing the model). Positioning of the models is done using matrices. The old OpenGL have some handy and easy-to-use functions for rotating and translating objects. There are also functions for scaling the objects (changing size), so that is covered pretty easy. All you need is to figure out camera position, relative to the marker (which i believe is implemented in OpenCV).
If you were to use the forward-compatible OpenGL, you would need to set up vertex buffer objects to contain model data and write vertex and fragment shaders to shade and display your model. That's kinda more work for which you get extended flexibility. But you can use shaders in the old OpenGL as well, if you decide you need them (eg. for some special effects).
Learning how to use a scenegraph or an engine (ogre) can take some time, i would not recommend it for your task.
I'm new to graphics, and I have to make a model of a building for an assignment using only GLUT or OpenGL.
Basically the school building's model( only the exterior portion) is to be made, and I have no clue where to start. Upto now I have drawn polygons, other shapes using GLUT, nothing in which there are multiple shapes. All the drawing upto now is using lines, or points, or polygons and mathematics.
Could you please give me an idea of how to go about it?
Update: I just want to know what steps I can follow to get it done. Some reference links would be awesome!
You could use modeling programs to create your model, and then use tools such as COLLADA to get your model into OpenGL.
The problem with hand-coding a complex object like that is that it takes a great number of lines of code just to define the vertices of the object.
People usually use 3D modeler software to build complex 3D objects, like Maya, 3DSMax or Blender and then export them in a format to be read into your OpenGL application.
Think about what you want your building to look like, and think about what kind of triangles you need to render in order to make that. You can either draw the entire thing in some sort of modelling software, and then import it into OpenGL, or you can come up with the triangles/textures yourself and do it by hand in OpenGL.
The exterior of the building will probably have a similar texture on the whole thing (brick, etc), and then there will be windows, doors, and a roof. Maybe some sort of sign that says "School Building". Take this all into account, what exactly you want your building to look like, and then think about what textures you will need to draw these things.
For example, say you're doing a brick building that is in the shape of a box, with a door and a few windows. I'd use one texture for the brick, and first draw an entire wall of brick. Then, I'd use a grey/blue looking texture for the window, and draw it over the brick wall. Then I'd do the same (different texture) for the door.
Just think about the design, and then just try things out - experiment. Good luck!
I once had a simillar homework. I did it by creating the models with Google SketchUp, then export the models to .3ds file and use my program to render it.
I choose Google SketchUp because it's the easiest to use among those tool I tried. Plus, they had a discount for students. You could also use Blender, which is free but take too much time to learn IMHO. 3dsMax is too expensive to pay for a homework.
To load the model into my program, I used Assimp library.
I am trying to develop a 3D game in openGL and i need to create many 3D objects.. I am a begginner in openGL.. I have tried with many 3D softwares like Blender , MODO, Unity 3D and Cheetah.
I am easily able to create my objects with these and exporting as Wavefront .OBJ, and converting it to a header file using a perl script. This header file is added to my openGL project..
The 3D objects are seen, but its not perfect. The script i used is to convert the .OBJ to .h using TRIANGLES.. And the object is seen with triangles. Its not full.. No way when i used TRIANGLE STRIP,FAN..? Problems with the vertices..
Is the problem with my Script or is it the wrong way i have gone..?? Or is there any other best ways to directly import 3D objects to openGL..??
The below link is the best one which you can get for 3D objects to openGL.. i got the scripts from these..
http://www.heikobehrens.net/2009/08/27/obj2opengl/
please help..
You don't want to go that way. Direct drawing mode (using TRIANGLE and friends) is extremely slow in OpenGL.
Instead, you should pick a decent format and write a loader for it (or use one found on the web). Good formats would be 3ds, obj if gzipped, collada.
Here's an example tutorial on loading from Milkshape files.
Once you load your objects programatically, you can use Vertex Arrays, or even better VBO's to display them. This is waaay faster.
Google for a mesh loader for your favorite format, or write one yourself.
I have written a reader/renderer for AC3D files that works fine on the iPhone (OpenGL ES)
Feel free to have a look at it here.
There is also an obj loader by Jeff Lamarche at google code.
AC3D can reduce the triangle count pretty good and as an alternative I ported QVis to the mac. My reader/renderer also tries to build tri-strips.
About VBO's. I have not seen any gained performance when using them in the iPhone. I'm not the only one.