Sign in to follow this  
Ali_nz

OpenGL Texturing

Recommended Posts

Hi guys, Pretty much a newbie here so bear with me. I will try to explain what I am trying to do as best as I can. I am in OpenGL and VC++ Express. I am trying to create a instrument used in a airplane called a Artifical Horizon - or the glass cockpit version is called a PFD. Picture at: http://www.flypfc.com/project%20magenta/jpegs/PFD%20BOEING%20ENH.jpg I have created a 640x480 window - although it can be resized. I have put a quad in the window. The top half of the quad represents 180 degress and the bottom half represents 180 degrees. Now I have successfuly done the following: * Created a quad 36 heigh x 1 wide (36 because ultimately its divided into 360 degrees) * Textured the quad *Applied a mask so that only about 30 degrees worth is shown at one time one of the problems i have run into is that where the blue and brown meets (see pic) their is a 1 pixel wide white line running between them. I created a bmp 256 wide and 4096 heigh - a huge texture. I figured that if I created the texture any smaller the stretching would make the 1 px wide white line bigger than 1 px - or am I missing something here? Also I find that the 1 pixel wide white line tends to get aliasing - is their a way to fix aliasing on textures? What program would be good for making textures? I have been using PShop, but its not very good for exact placement of thin lines. I was also googling on this subject the other day and saw something about Ortho2d where you can make the coordinates directly relate to pixels? This might be good for this project? Cheers -Al

Share this post


Link to post
Share on other sites
I can't see any specific need to use texturing to do the drawing, not from that image anyway. Its all vectors and polygons.
Orthographic projection just means that no perspective is applied to points before rasterizing them. Normally in perspective projection the x and y coordinates are divided by the z coordinate, which has the effect of making objects further away appear smaller on the screen.
Screen pixels do not necessarily map directly to screen pixels in orthographic projection, as all normal transforms can still be applied (scaling, rotation etc).
I would definitly be using orthographic projection to draw a 2D interface like this though.
To get rid of the aliasing on textures make sure you have the correct filtering set.
If you use vector drawing in you program to draw the interface you can apply antialiasing directly to the polygons and lines. I think it wouldn't probably look clearer, use less memory, and maybe run faster.

Share this post


Link to post
Share on other sites
Not really, you can draw curves using lines and cos+sin, but i would use a texture for all the bits in that image that are black (i.e the background). Then you can use it as a mask and make it different textures depending on what type of plane the user is flying (wood, steel, black plastic etc).

Share this post


Link to post
Share on other sites
Sorry which type of thing, curves, masking textures or just cockpit displays in general?
If you mean curves then:

// draw curved corners
degInc = 90.0f/(float)segments;
// top right 0 deg to 90 deg
glBegin(GL_TRIANGLE_FAN);
glVertex2f(xCenter, yCenter);
for(i=0, deg=0.0f; i<=segments; i++, deg+=degInc)
{
x = xCenter + cos(DEG_TO_RAD(deg)) * radius;
y = yCenter - sin(DEG_TO_RAD(deg)) * radius;
glVertex2f(x, y);
}
glEnd();



Masking textures, i really just mean use the alpha channel.
My guess for drawing the artifical horizon would be that you need to find out 2 values for the plane: the inclination (pitch) and the roll. Once you have those you can setup your code to firstly transform vertically by the inclination, then rotate by the roll, and draw the horizon and inclination starting from the middle of the display and going upwards (in local coordinated).

Share this post


Link to post
Share on other sites
Hmmm, any idea why this doesnt work:



int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer
glLoadIdentity(); // Reset The Current Modelview Matrix
glTranslatef(0.0f,0.0f,-5.0f);

glBegin(GL_QUADS); // Draw A Quad
glColor3f(0.0f, 0.6f, 0.796f);
glVertex3f(-1.5f, 18.0f, 0.0f); // Top Left
glVertex3f( 1.5f, 18.0f, 0.0f); // Top Right
glVertex3f( 1.5f, 0.0f, 0.0f); // Bottom Right
glVertex3f(-1.5f, 0.0f, 0.0f); // Bottom Left

glColor3f(0.694f, 0.4f, 0.0f);
glVertex3f(-1.5f, -18.0f, 0.0f); // Top Left
glVertex3f( 1.5f, -18.0f, 0.0f); // Top Right
glVertex3f( 1.5f, 0.0f, 0.0f); // Bottom Right
glVertex3f(-1.5f, 0.0f, 0.0f); // Bottom Left
glEnd();

glBegin(GL_LINES);
glColor3f(1.0f, 1.0f, 1.0f);

glVertex3f(-1.5f, 0.0f, 0.0f);
glVertex3f(1.5f, 0.0f, 0.0f);

glVertex3f(-0.6f, 1.0f, 0.0f);
glVertex3f(0.6f, 1.0f, 0.0f);
glEnd();


glEnable(GL_BLEND); // Enable Blending
glDisable(GL_DEPTH_TEST); // Disable Depth Testing
glBlendFunc(GL_DST_COLOR,GL_ZERO); // Blend Screen Color With Zero (Black)

glBindTexture(GL_TEXTURE_2D, texture[1]); // Move Right 3 Units
glBegin(GL_QUADS); // Draw A Quad
glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.0f, 2.0f, 0.0f); // Top Left
glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.0f, 2.0f, 0.0f); // Top Right
glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.0f,-2.0f, 0.0f); // Bottom Right
glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.0f,-2.0f, 0.0f); // Bottom Left
glEnd();

glDisable(GL_BLEND);

return TRUE; // Keep Going
}



I just get a black screen.

It worked with the textures, but if I try to apply the bmp mask to a colored quad as opposed to a textured quad it doesnt work????

-Al

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Announcements

  • Forum Statistics

    • Total Topics
      628334
    • Total Posts
      2982146
  • Similar Content

    • By DejayHextrix
      Hi, New here. 
      I need some help. My fiance and I like to play this mobile game online that goes by real time. Her and I are always working but when we have free time we like to play this game. We don't always got time throughout the day to Queue Buildings, troops, Upgrades....etc.... 
      I was told to look into DLL Injection and OpenGL/DirectX Hooking. Is this true? Is this what I need to learn? 
      How do I read the Android files, or modify the files, or get the in-game tags/variables for the game I want? 
      Any assistance on this would be most appreciated. I been everywhere and seems no one knows or is to lazy to help me out. It would be nice to have assistance for once. I don't know what I need to learn. 
      So links of topics I need to learn within the comment section would be SOOOOO.....Helpful. Anything to just get me started. 
      Thanks, 
      Dejay Hextrix 
    • By mellinoe
      Hi all,
      First time poster here, although I've been reading posts here for quite a while. This place has been invaluable for learning graphics programming -- thanks for a great resource!
      Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
      The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
      Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
    • By aejt
      I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.
      I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).
      This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:
      I have these classes:
      For GPU resources:
      Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO. Texture: holds and manages a texture which is loaded into the GPU. Shader: holds and manages a shader which is loaded into the GPU. For assets relying on GPU resources:
      Material: holds a shader resource, multiple texture resources, as well as uniform settings. Mesh: holds a geometry and a material. Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on? For handling GPU resources:
      ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector) Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).  
      And my plan is to define everything into these XML documents to abstract away files:
      Resources.xml for ref-counted GPU resources (geometry, shaders, textures) Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on) Are reference counted using ResourceCache<T> Assets.xml for assets using the GPU resources (materials, meshes, models) Assets are not reference counted, but they hold handles to ref-counted resources. References the resources defined in Resources.xml by names/ids. The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:
      Factory classes for resources:
      For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.
      Factory classes for assets:
      Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).
       
       
      Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!
      Thanks!
    • By nedondev
      I 'm learning how to create game by using opengl with c/c++ coding, so here is my fist game. In video description also have game contain in Dropbox. May be I will make it better in future.
      Thanks.
    • By Abecederia
      So I've recently started learning some GLSL and now I'm toying with a POM shader. I'm trying to optimize it and notice that it starts having issues at high texture sizes, especially with self-shadowing.
      Now I know POM is expensive either way, but would pulling the heightmap out of the normalmap alpha channel and in it's own 8bit texture make doing all those dozens of texture fetches more cheap? Or is everything in the cache aligned to 32bit anyway? I haven't implemented texture compression yet, I think that would help? But regardless, should there be a performance boost from decoupling the heightmap? I could also keep it in a lower resolution than the normalmap if that would improve performance.
      Any help is much appreciated, please keep in mind I'm somewhat of a newbie. Thanks!
  • Popular Now