I want to create a robot and want to move it in OpenGL. I will create the model in 3DsMax.
I was wondering about importing and moving it in OpenGL.
In which format should I save my file in 3ds Max so that I can import it in OpenGL?
Should I use pivots or save each part of the robot as a seperate file?
Does OpenGL support pivots?
OpenGL has surprisingly little to do with the answer. OpenGL is only used to draw your geometry. It is not a rendering/game engine/scenegraph in itself. Therefore loading a mesh and animating it is something you should take care of, subsequently informing OpenGL what it has to draw.
You can however make your life a bit easier by looking for OpenGL based rendering/game engines/scenegraphs out there that already provide the support you desire. But you'll have to take a look at that yourself. Then export your mesh in whatever suitable format your engine supports. OpenGL itself holds no relevance to whatever file format you wish to use. If you or your engine can deal with it and get all the relevant information out of it, you can use it.
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I am an openGL beginner. I need to build a c/c++ application which displays 3d models in augmented reality. For AR i'm using ARToolkit. In the app it must import 3d models built with modelling softwares like blender,sketchup etc.. the models might be .obj,.3ds,.collada(suggest me any others if any??).
ARToolkit mainly uses opengl to render(AFAIK), the 3d objects to camera input.
Is it possible to load 3d models/objects at runtime dynamically. what libraries are existing if any for this?
I want to have keyboard interaction with the models also where i can move specific parts of the model(eg: rrotate wheels of a car)
The models here maybe as simple as a simple house to character(man/woman).suggest me the resources i need for this and any technicalities i missed. I prefer if possible my code to work with opengl 1.4
You will need some import mechanism to import meshes in various formats into your runtime format. OpenGL (or DirectX) doesn't specify how your meshes must look on disk, and there is various stuff stored on disk that is not required for rendering. Basically, you need a way to get the vertex positions and attributes from the file, and optionally an index list (if you render using indexed triangle lists, which you probably should be doing.)
The easiest for sure is .obj, which is an ASCII format that you can easily parse and which is supported by many applications. Otherwise, look at libraries like Open Asset Import.
However, I would assume you are looking for an OpenGL based rendering system, which does the rendering for you as well as the mouse interaction. There are lot of existing engines you can use out there, for instance, Ogre3D or IrrLicht. IrrLicht is easy to use and provides support for a bunch of the formats you mentioned. It you must stick with ARToolkit for rendering, then you can probably easily convert the formats from either engine to whatever ARToolkit expects.
I'm very recomending you to try http://assimp.sourceforge.net/lib_html/
It supports a lot of open/not-very-open data formats, skelet-animation, affine transfer animation, etc.
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'm making a renderer using OpenGL. I have textured models in Blender / Sketchup (I can exchange between the two easily), and I'd like to be able to export those files into my renderer. My initial idea was to simply export the raw faces and render those triangles, but I'd like to easily slice my texture files into texture coordinates as well.
By that, I mean that my model faces get carved into triangles. You can see in this image (reproduced below) that my curve becomes 24 triangles. I would like to know what texture coordinates to use for each triangle.
Would a DAE file be the easiest way to do that? I've been reading the specs for the format and it looks easy enough. I think I could parse the XML and faithfully recreate the models in OpenGL. I'm wondering if there is an easier way (i.e. one that doesn't reinvent the wheel).
If you're comfortable with parsing the .dae-format, sure use it. However, if you're only interested in exporting textured triangle meshes I would consider using the .obj format which is much more simple to parse. From what I can tell both Sketchup and Blender can export this format.
If binary formats don't scare you, I'd suggest writing a Blender & Sketchup plug-in and exporting the geometry pre-baked into packed vertex arrays.
The beautiful thing about this method is that there's no parsing or type conversion in your app. Everything is ready to be sent to the GPU in simple contiguous memory copies. Great for static geometry.
A stripped down blender exporter looks something like this:
#!BPY
import bpy, struct
from Blender import *
self.fh = open("MyFileName", "w")
m = bpy.data.meshes["MyMeshName"]
faces = m.faces
for face in faces:
for (vertex, uv) in zip(face.verts, face.uv):
self.fh.write(struct.pack('<fff', *vertex.co)) # coords
self.fh.write(struct.pack('<fff', *vertex.no)) # normals
self.fh.write(struct.pack('<ff', uv.x, uv.y)) # uvs
self.fh.close()
If you wish to parse .dae files, i would suggest to look into Collada parsers.
.dae is actually the extension for Collada files, the latest effort from the Khronos group (maintainers of OpenGL) to have a single unified file format for 3D data exchange.
As for the existing parsers, here is what I've come across:
collada-dom, the reference implementation. As the name suggests, it is just an abstraction of the XML tree.
FCollada, a nicer abstraction. However, this project has been dead for almost two years, and, from what I've gathered, it is unlikely that we'll see any update in the future.
OpenCollada, a recent new effort. Haven't tried it, but there is an active community behind it.
That being said, if your only goal is loading a simple piece of geometry with vertices, normals and texture coordinates, going with the .obj file format might be a quicker way.
Any decent file format used by modeling programs (such as Blender or Sketchup) will include all information necessary to recreate the geometry you see. This should include the geometry type (e.g. triangle strips, individual triangles, etc), the vertices and normals for the geometry, the material properties used, and also the textures used along with the appropriate texture coordinates. If anything is lacking from a potential file format, choose another one.
If you think that parsing XML is simple, then I hope you're planning on using existing libraries to do this, such as expat, Xerces, or some other language specific implementation.
When considering import/export, first try to find an open source library that can handle the import for you and make the data available to your program in a reasonable format. If that's not available, and you must write your own importer, then try to find a simple ASCII (not XML-based) or binary format that fits your needs. PLY might be suitable. Only as a a last resort, would I recommend trying to implement an importer for an XML-based format.
There's also:
Lib3DS - http://www.lib3ds.org/
LibOBJ (won't let me post link)
You should take a look at:
http://sketchup.google.com/community/developers.html
The sketchup team provides a C++ COM server for free. Using this, you can get access to lots of information about a .skp file.
You should be able to use this COM server to write a .skp importer for your application.
You should try to get the .tlb file if you can. This will give you access to smart pointers, which will simplify your importer (COM client)
I used the version 6 SDK (which included the tlb file). The current version of the SDK does not appear to include this file.
Someone posted a solution (for the missing tlb file) on the developer forums:
http://groups.google.com/group/su-sdk-fileshare/topics