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The Magical Pot

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About The Magical Pot

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  1. VBO and glIsBuffer

    I managed to fix this at last. The call stack said that the error occurred after main was called and I realized that I used an incorrect method at first to check where the application crashed. When the application was to delete an object of type VBOQuad, I checked if the object existed in memory by comparing it to NULL, but I tried to print out the value of an uninitialized pointer of this type and I realized that such a pointer is not necessarily equal to NULL. In the end, an uninitialized pointer was seen as an initialized one, thus the application would try to delete an object that didn't exist in memory.   Thanks for your help! :)
  2. VBO and glIsBuffer

    Hi!   I'm working with VBOs and I suddenly sumbled across a very weird error. My compiler is giving me a run-time error saying that this statement can't be executed: if ( glIsBuffer( VertexBuffer ) ) This statement can be found in this destructor: VBOQuad::~VBOQuad() { //Clear vertex buffer if ( glIsBuffer( VertexBuffer ) ) glDeleteBuffers( 1, &VertexBuffer ); //Clear index buffer if ( glIsBuffer( IndexBuffer ) ) glDeleteBuffers( 1, &IndexBuffer ); VertexBuffer = NULL; IndexBuffer = NULL; } I've tried to track this error down to find some sort of context, but I've found that the run-time error emerges before the first line of the main function is executed. The description of glIsBuffer says that the function will return true if the argument is the name of an existing buffer, and it will return false if the argument is zero or a non-zero value. The debugger says:   VertexBuffer CXX0030: Error: expression cannot be evaluated IndexBuffer CXX0030: Error: expression cannot be evaluated     This would, to me, indicate that VertexBuffer doesn't exist in memory, which in turn would mean that VertexBuffer is basically NULL, which is defined as zero, so there souldn't be a problem. That's probably not right since it's crashing at that statement.   The main problem I'm having is that the application crashes before the main function is executed, so for all I know, the destructor hasn't even been called yet, but it's trying to execute it, by the looks of it. My question is what the problem usually is in a situation like this where the application crashes before the main function is executed.   Thanks!   EDIT: I have added a screen dump of the Stack Trace.
  3. Uptading parts of data in a VBO

      I feel like GLSL is a little too much for me at this point. Would you say that it's better to replace both the vertex data and the texture coordinates rather than partially update in this case when it comes to performance?
  4. Uptading parts of data in a VBO

    Thank you both! I solved the problem by splitting the VBO into 2 parts, one for vertecies and one for texture coordinates. I didn't really know you could do that.   Cheers!
  5. Hi!   I'm currently trying to set up a function that renders a textured 2D quad using VBOs. The function changes the vertex data of the VBO every time it's called so that you can stretch it, but the texture data of the VBO doesn't change. In other words I want to be able to change the vertex data without having to change the texture data of the VBO.   When I store my VBO I have a struct that contains 4 GLfloats (VertexData2D), the first two GLfloats represent the vertex data and the last two GLfloats represent the texture data. My problem is that I can't find a way to only change the vertex data without having to change the texture data, since the entire VBO contains both vertex data and texture data.   This the rendering part in the function: glBindTexture( GL_TEXTURE_2D, get_texture_id() ); //Set texture //Enable vertex and texture coordinate arrays glEnableClientState( GL_VERTEX_ARRAY ); glEnableClientState( GL_TEXTURE_COORD_ARRAY ); glBindBuffer( GL_ARRAY_BUFFER, VertexDataBuffer ); //Bind vertex data //Update vertex buffer data glBufferSubData( GL_ARRAY_BUFFER, 0, 4 * 4 * sizeof(GLfloat), VData ); //Set texture coordinate data glTexCoordPointer( 2, GL_FLOAT, 4 * sizeof(GLfloat), (GLvoid*)offsetof( VertexData2D, TexCoord ) ); //Set vertex data glVertexPointer( 2, GL_FLOAT, 4 * sizeof(GLfloat), (GLvoid*)offsetof( VertexData2D, Position ) ); //Draw quad using vertex data and index data glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, IndexBuffer ); glDrawElements( GL_QUADS, 4, GL_UNSIGNED_INT, NULL ); //Disable vertex and texture coordinate arrays glDisableClientState( GL_TEXTURE_COORD_ARRAY ); glDisableClientState( GL_VERTEX_ARRAY ); I first bind the correct texture and VBO, then update the VBO using glBufferSubData()   (the VBO is set with GL_DYNAMIC_DRAW). I update the VBO starting at index 0, VData is the VBO that's going to replace the current one. Each vertex has the size  4 * sizeof(GLfloat) and since I'm rendering a quad, the stride results in 4 * 4 * sizeof(GLfloat) It's in glBufferSubData() that the problem is, my VBO contains both the vertex data and texture data, but I only want to change the vertex data. glBufferSubData() overwrites the current VBO, but I only want it to overwrite parts of it. This is essentially how I want it to work:   Update memory equal to: 2 * sizeof(GLfloat) Skip memory equal to: 2 * sizeof(GLfloat) Repeat 3 more times   What should I do? Is there another function that can do this?   Thank you!
  6. Using cosine, sine, tangent etc. in C++

    I asked a very simple question and I got the answer that I needed 5 minutes after posting. I know that you shouldn't ask stuff that you can easily find on google or whatever, but for some reason i did and someone was nice enough to answer my question. I'll gladly take delete this post if anyone says that I have to because I already got my answer. This conversation is pointless.
  7. Using cosine, sine, tangent etc. in C++

      Everyone doesn't study math in english, I didn't know that "cos-1" was "arc cosine" in english.
  8. Using cosine, sine, tangent etc. in C++

    Hi!   I don't need to go into detail of what I'm doing to get an answer on this question. All I'm wondering is what function in the cmath.h header that corresponds to cos-1, sin-1, tan-1 on a calculator. For example: if I want to calculate cos-1(200/100) to get the degree of an angle, which function do I use since functions cos(), sin(), tan() in C++ corresponds to cos, sin, tan on a calculator and not cos-1, sin-1, tan-1.   Hopefully, that was not a load of incohesive dribble, but let me know if you want me to explain some more if it was :)
  9. what engine & language?

    When you want to start programming games you don't start off with games like Starcraft or Age of Empires 2 etc. those games are actually quite coplex. You'll want to start with something simple like pong, tetris and things like that. If you doubt me, I've actually have learned the hard way why you should start off simple: The first game I made was a 2D RPG and that dragged on for about 2 years, the engine I wrote for that was a mess and complete crap; I didn't know what I was doing. So basically, start off with smaller projects that don't take a whole lot of time to make, maybe a few months at most.   When it comes to languages and engines, it depends. If you want to create games as a hobby, using an existing engine might be a thing, but I'm not sure if I would recommend it. If you want to work towards a goal, like becomming a professional programmer, I would definately not recommend using an existing engine. I personally started with C++ (with SDL for 2D rendering), but that's not something I would neccessarily recommend to everyone since it does take a lot of effort to learn that. You could perhaps try something like Java or C.
  10. Utilizing the alpha channel on an image with OpenGL

    It might actually be the case that SDL only supports colorkeying and not blending, that might explain it since I've successfully used SDL for colorkeying while blending didn't work.
  11. Utilizing the alpha channel on an image with OpenGL

    Ok, I gave up on SDL's image loading thingy and switched over to DevIL and it worked perfectly. For me I just added this piece of code right after I initialized OpenGL: glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glEnable( GL_BLEND ); This will basically enable blending (check out http://www.opengl.org/sdk/docs/man/xhtml/glBlendFunc.xml for more information about glBlendFunc).   To find out how to install and load images with DevIL into OpenGL textures, I'd recommend this link: http://lazyfoo.net/tutorials/OpenGL/06_loading_a_texture/index.php   Note: for Visual Studio users, you have to open up 'ilu.h' and replace the line: #include <IL/il.h> With: #include <il.h> Since Visual Studio don't include certain files in the same way that other IDEs do.   That worked for me, I hope it works for anyone else who's having the same problem :)
  12. Utilizing the alpha channel on an image with OpenGL

    I still don't know how to check such information, but it seems like there shouldn't be anything wrong with the pixels since the textures work fine when blending isn't enabled. It however seems like this problem isn't really going anywhere, so I could try with the DevIL image loading library instead of SDL's one.
  13. Utilizing the alpha channel on an image with OpenGL

    The values for image->w and image->h are correct, I have no idea about how to check image->pixel which is a pointer of type void, but when I write image->pixels as an integer, the output for a 32x32 texture is "86048840" if that says anything.   I searched a bit more about other people who have the same problem, but the only solution I've found was to switch over to the DevIL which takes care of image loading.
  14. Utilizing the alpha channel on an image with OpenGL

    It didn't solve the problem. I forgot to add a piece of code, I bind the texture right before I render it: glBindTexture( GL_TEXTURE_2D, ThemeTemplate->TemplateSheet->get_data() ); //Set texture ID I really don't know what the problem is, but maybe it has something to do with the arguments passed when I enable blending?
  15. Utilizing the alpha channel on an image with OpenGL

    Yes, there's a line in the last code snippet 'bool Texture::load_texture( SDL_Surface *image )' where I call that function // Bind the texture object glBindTexture( GL_TEXTURE_2D, data ); This line is executed before I draw anything.   I also forgot to show the picture, so here it is: https://twitter.com/TheMagicalPot/status/359349302939754496   "The Image in this post shows what the application renders without the enabling of blending on the left side, the right side is what it renders when I enable blending. The blue window within the application is made out of pieces of textures for the frame and the center is a colored quad, so when I render textures, they're not shown, but when I render geometrical shapes without textures, they're shown."
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