I've encountered a problem whilst learning how to texture in OpenGL (from OpenGL 5th Edition Bible). The problem is that I can't display my texture. I load it from a BMP file with a function I've written myself.
Since code is quite lengthy I uploaded all neccessery files. You can download it from here.
EDIT: I've tried copying code from the mentioned book (TGA loading described there) and it doesn't work as well. It seems that loading stucks at loading image data from file (strange). I suppose it isn't relevant as far as my problem is concern.
There are general debug steps for checking for problems. I will list them below in the hope you might find the bug (and for future readers):
Does the file exist? Is the file being read properly according to the format? Did you get it to gel well with OpenGL? My suggestion: Do not mess with these things yourself. Use a library. There's an amazingly light weight SOIL (Simple OpenGL Image library)
Are you loading the textures before initialising OpenGL? This was always my problem because I used to "load" and do a glBindTexture(..) in the constructor (of some class). The objects were created before OpenGL was initialised.
Have you enabled GL_TEXTURE_2D? Check the initialise code, use: glEnable(GL_TEXTURE_2D)
Did you map the textures properly with the quad or the shape you want it on? Expanding on this here is (sort of) out of scope. There are great tutorials out there.
(Would seem stupid, but happens sometimes) Are you blacking out the object by glColor3f(0,0,0) ?
There could be more checks, but these are the ones hitting my head now
Related
Context
I'm a beginner in 3D graphics and I'm starting out with Vulkan, which I already know it's not recommended save it please, currently working on a university project to develop the base of a 3D computer graphics engine based on the Vulkan API.
The problem
Example of running the app to render the classic 2D triangle
Drawing a 3D mesh after having drawn the triangle
So as you can see in the images above I want to be able to:
Run the engine.
Choose an object to be drawn.
Close the window.
Choose another object to be drawn.
Open the same window back up with only the last object chosen visible.
And the way I have been doing this is by essentially cleaning up the whole swap chain and recreating it from scratch once the window is closed and a new object has been chosen. Now I'm aware this probably sounds like terrorism for any computer graphics engineer but the reason I'm doing this is because I don't know a better way, I have just finished the vulkan tutorial.
Solutions tried
I have checked that I do a vkDestroyBuffer and vkFreeMemory on the current vertex buffer before recreating it again once I choose a different object.
I have disabled depth testing entirely in case it had something to do with it, it doesn't.
Note: The code is extensive and I really don't have a clue of which part of it could be relevant to the problem, so I opted for not cluttering the question, if there is an specific part you think it might help you find the solution please request it.
Thank you for taking the time to read my question.
A comment by user369070 ended up drawing my attention to the function I use to read OBJ files which made me realize that this function wasn't cleaning a data structure I use to store the vertices of the object chosen to be drawn before passing them to the vertex buffer.
I just had to add vertices = {}; at the top of the function to solve it.
I started working at this company that uses an 2D OpenGL implementation to show our system's data (which runs on Windows.) The whole system was built with C++ (using C++Builder 2007). Thing is, all the text they print there are pixelized when you zoom in, which I think happens because the text is a bitmap:
From what I know they use the same font files as Windows does. I asked around here on why this happens and the answer I got is that the guy who implemented it (which doesn't work at the company anymore) said fonts on OpenGL are hard and this was the best he could do or something like it.
My question is: is there any simple and effective way to make the text also a vector (the same way those lines in the picture are?) So when I zoom the camera, which happens a lot, they don't pixelize. I have little knowledge of OpenGL and if you have some guide and/or tutorial related to this to point me towards the right direction I'd be very thankful. Basically any material would be great.
Most of OpenGL text rendering libraries come to this: creating bitmaps for the fonts. This means you are going to have problems with scaling and aliasing unless you do some hacks.
One of the popular hacks is Valve's approach: Chris Green. 2007. "Improved Alpha-Tested Magnification for Vector Textures and Special Effects.". You use signed distance field algo to generate your fonts bitmap which then helps you to smooth the text outlines on scale during rendering. Wikidot has the C++ implementation for Distance field generation.
If you stick to NVidia specific hardware, you can try the NVidia Path extension which allows you to render graphics directly on GPU. Remember, it is a NVidia only thing.
But in general, signed distance field based approach is the smoothest and easiest to implement.
BTW, freetype-gl uses Valve's approach and also the modern pipeline.
You can try freetype-gl its a library for font rendering in OpenGL.
The issue with using fonts in OpenGL is that they are handled inconsistently across platforms, and that they have minimal support. If you're willing to go with a helper library for OpenGL (SDL comes to mind), then this behaviour will likely be wrapped, meaning that you merely need to provide a suitable font file for them to use.
You may try out FTOGL4 , the fonts for OpenGL4
I'm working on a simple 3D model loader using OpenGL and I wanted to add texture support. However, not wanting to needlessly rewrite an image library, I downloaded SOIL (Simple OpenGL Image Library) that I learned about in the NeHe tutorial on texture mapping. It has a few very useful functions that take care of loading images of many times and passing them to OpenGL.
The problem is this: In the NeHe tutorial code, the SOIL function
SOIL_load_OGL_texture(char *, param,param,param)
exactly as promised and the polygons are mapped with the correct picture. However, I've made a class that loads OBJ and MTL files (3D model files). When I try to use the SOIL function to load a texture inside this class, my program crashes.
I am using GNU C++ with Code::Blocks (I also tried this code in Dev-C++)
I receive no errors or warnings from the compiler with -g -Wall.
I have linked and included everything properly in my project (if I copy/paste the NeHe code, it runs properly).
The SOIL command does not work inside any class (I tried making another class that only executed the SOIL function and I got the same problem).
The file paths passed to the function are all correct. I have tried relative and absolute, with all formats of forward and back slashes. I copied and pasted absolute paths that worked in the NeHe code to my code and it does not work.
The rest of my code works fine - I can get my shape rendered with its ambient/diffuse/etc. colors and other settings applied properly.
Sounds almost like you don't have a valid OpenGL context at the time when you're calling that function.
Are you certain that SOIL is called only after your opengl context is initialized? (e.g. no static construction of objects that are constructed at program initialization). A quick way to check this is to put a breakpoint on your opengl initialization and see if you hit the BP or if your program crashes first.
Also, make sure that SOIL call is on the same thread as your opengl context.
I am taking an OpenGL course and we have the option to create models to use in our assignments with a 3D modeling application, like Maya or Blender.
I am not looking forward to typing in coordinates manually so I was curious what resources I should be looking into for writing OpenGL code and importing models. (Textures are coming later). I am also concerned by the scale I'm importing at but maybe that's silly to worry about at this point.
Thanks for any resource suggestions. OpenGL has so much out there I get overwhelmed sometimes when Googling for what I need.
EDIT:
This is what I ended up using.
http://www.spacesimulator.net/tut4_3dsloader.html
I downloaded the "Windows" version and with a few path changes to the includes, got up and running. It doesn't handle OBJ files but rather 3DS. Cheetah 3D exports to this type as well.
Blender can save files in .obj format, and a simple google search turns up several libraries for loading this into OpenGL. Here is one.
One of the simplest formats that can be used to export meshes is Wavefront OBJ (please search for it on Wikipedia as I'm only allowed to post one link at the moment). It's basically a text file that shouldn't be too hard to parse.
Or actually, if you're allowed to use GLUT, you could try and use its loader (as answered in OpenGL FAQ 24.040)
Don't worry about the object scale at the moment, you can always scale your object later. Just make sure you export it with local coordinates, not global (e.g. [0,0,0] should be the center of the object, not the world you're modelling).
I'd suggest not worrying about the scale of the objects for right now.
Now, the thing you're going to have to do is settle on a format for the 3D file. There are MANY options when exporting from a 3D program like Maya or Blender.
Might I recommend attempting a simple COLLADA importer. Specification information is here:
http://www.khronos.org/files/collada_spec_1_4.pdf
Another spec I've been using lately would also probably be suitable for this is OBJ.
The specification for OBJ is located here:
http://local.wasp.uwa.edu.au/~pbourke/dataformats/obj/
Also, there are several free sample 3D OBJ files located here. This will allow you to see the format of the files and really see how easy they can be to parse.
Keep in mind, OBJ can not support animation, and it is rather inefficient for rendering large scenes.
I'd say that the Obj format is a good balance for readability and functionality if you want to parse it yourself.
http://en.wikipedia.org/wiki/Obj
The easiest way would to be to find a library to do it for you but the possibilities would be limited to your chosen language.
You shouldn't be worrying about scale. OpenGL's matrices can easily rescale vertices.
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.