Sign in to follow this  
Qureshi

OpenGL Can any body help me with the piece of code

Recommended Posts

/* I found this code from this site http://www.videotutorialsrock.com/ In this code can anybody plz tell me that how main is called who is providing argument to the main parameters ? */ #include<iostream> #include <stdlib.h> //#include <GLUT/glut.h>//////////////these are for mac #include <GL/glut.h> using namespace std; void handleKeypress(unsigned char key, //The key that was pressed int x, int y); void initRendering(); void drawScene(); void handleResize(int w, int h); int main(int argc, char** argv) { //Initialize GLUT glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); glutInitWindowSize(400, 400); //Set the window size //Create the window glutCreateWindow("Basic Shapes - videotutorialsrock.com"); initRendering(); //Initialize rendering //Set handler functions for drawing, keypresses, and window resizes glutDisplayFunc(drawScene); glutKeyboardFunc(handleKeypress); glutReshapeFunc(handleResize); glutMainLoop(); //Start the main loop. glutMainLoop doesn't return. return 0; //This line is never reached } void drawScene() { //Clear information from last draw glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_MODELVIEW); //Switch to the drawing perspective glLoadIdentity(); //Reset the drawing perspective glBegin(GL_QUADS); //Begin quadrilateral coordinates //Trapezoid glVertex3f(-0.7f, -1.5f, -5.0f); glVertex3f(0.7f, -1.5f, -5.0f); glVertex3f(0.4f, -0.5f, -5.0f); glVertex3f(-0.4f, -0.5f, -5.0f); glEnd(); //End quadrilateral coordinates glBegin(GL_TRIANGLES); //Begin triangle coordinates //Pentagon glVertex3f(0.5f, 0.5f, -5.0f); glVertex3f(1.5f, 0.5f, -5.0f); glVertex3f(0.5f, 1.0f, -5.0f); glVertex3f(0.5f, 1.0f, -5.0f); glVertex3f(1.5f, 0.5f, -5.0f); glVertex3f(1.5f, 1.0f, -5.0f); glVertex3f(0.5f, 1.0f, -5.0f); glVertex3f(1.5f, 1.0f, -5.0f); glVertex3f(1.0f, 1.5f, -5.0f); //Triangle glVertex3f(-0.5f, 0.5f, -5.0f); glVertex3f(-1.0f, 1.5f, -5.0f); glVertex3f(-1.5f, 0.5f, -5.0f); glEnd(); //End triangle coordinates glutSwapBuffers(); //Send the 3D scene to the screen } void handleResize(int w, int h) { //Tell OpenGL how to convert from coordinates to pixel values glViewport(0, 0, w, h); glMatrixMode(GL_PROJECTION); //Switch to setting the camera perspective //Set the camera perspective glLoadIdentity(); //Reset the camera gluPerspective(45.0, //The camera angle (double)w / (double)h, //The width-to-height ratio 1.0, //The near z clipping coordinate 200.0); //The far z clipping coordinate } void initRendering() { //Makes 3D drawing work when something is in front of something else glEnable(GL_DEPTH_TEST); } void handleKeypress(unsigned char key, //The key that was pressed int x, int y) { //The current mouse coordinates switch (key) { case 27: //Escape key exit(0); //Exit the program } }

Share this post


Link to post
Share on other sites
Quote:

In this code can anybody plz tell me that how main is called who is providing argument to the main parameters ?

The "runtime".

What happens is that the operating has a convention of how it starts a process and how it passes information to it. When your process is started, a piece of code that has been written for you translates the information into a way that main can understand, and then calls main(). When main returns, the runtime translates the error code into a way the host operating system can understand.

It basically acts as a buffer between you and the specifics of the OS, so that code can be made to work under different operating systems without being rewritten.

An interesting fact is that C++ forbids the user from calling main() themselves, whereas in C you can make main recursive. This is, of course, rarely used outside obfuscation competitions.

Share this post


Link to post
Share on other sites
"An interesting fact is that C++ forbids the user from calling main() themselves, whereas in C you can make main recursive. This is, of course, rarely used outside obfuscation competitions."

When you say 'forbids', do you mean the compiler will generate an error message
or the recursive call won't be called?

Share this post


Link to post
Share on other sites
That the standard explicitly say you must not do it. But like pretty much everything else forbidden in C++, all that means is undefined behavior if you do it anyway, and that you, the programmer, knows that and won't do it. From the compilers perspective, you are expected to know that (and plenty of other things for that matter), and don't do it. Scary, eh?

Share this post


Link to post
Share on other sites
I can't understand the working of glNormal3f(0.0f, 0.0f, 1.0f); what this statment is doing when it is being used in this code, i got this code from this site.
" www.videotutorialsrock.com "

#include <iostream>
#include <stdlib.h>

#ifdef __APPLE__
#include <OpenGL/OpenGL.h>
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

using namespace std;

//Called when a key is pressed
void handleKeypress(unsigned char key, int x, int y) {
switch (key) {
case 27: //Escape key
exit(0);
}
}

//Initializes 3D rendering
void initRendering() {
glEnable(GL_DEPTH_TEST);
glEnable(GL_COLOR_MATERIAL);
glEnable(GL_LIGHTING); //Enable lighting
glEnable(GL_LIGHT0); //Enable light #0
glEnable(GL_LIGHT1); //Enable light #1
glEnable(GL_NORMALIZE); //Automatically normalize normals
glShadeModel(GL_SMOOTH); //Enable smooth shading
}

//Called when the window is resized
void handleResize(int w, int h) {
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0, (double)w / (double)h, 1.0, 200.0);
}

float _angle = -70.0f;

//Draws the 3D scene
void drawScene() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glTranslatef(0.0f, 0.0f, -8.0f);

//Add ambient light
GLfloat ambientColor[] = {0.2f, 0.2f, 0.2f, 1.0f}; //Color (0.2, 0.2, 0.2)
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientColor);

//Add positioned light
GLfloat lightColor0[] = {0.5f, 0.5f, 0.5f, 1.0f}; //Color (0.5, 0.5, 0.5)
GLfloat lightPos0[] = {4.0f, 0.0f, 8.0f, 1.0f}; //Positioned at (4, 0, 8)
glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0);
glLightfv(GL_LIGHT0, GL_POSITION, lightPos0);

//Add directed light
GLfloat lightColor1[] = {0.5f, 0.2f, 0.2f, 1.0f}; //Color (0.5, 0.2, 0.2)
//Coming from the direction (-1, 0.5, 0.5)
GLfloat lightPos1[] = {-1.0f, 0.5f, 0.5f, 0.0f};
glLightfv(GL_LIGHT1, GL_DIFFUSE, lightColor1);
glLightfv(GL_LIGHT1, GL_POSITION, lightPos1);

glRotatef(_angle, 0.0f, 1.0f, 0.0f);
glColor3f(3.0f, 2.0f, 0.0f);



glBegin(GL_QUADS);

//Front
glNormal3f(0.0f, 0.0f, 1.0f);
glNormal3f(-1.0f, 0.0f, 1.0f);
glVertex3f(-1.5f, -1.0f, 1.5f);
glNormal3f(1.0f, 0.0f, 1.0f);
glVertex3f(1.5f, -1.0f, 1.5f);
glNormal3f(1.0f, 0.0f, 1.0f);
glVertex3f(1.5f, 1.0f, 1.5f);
glNormal3f(-1.0f, 0.0f, 1.0f);
glVertex3f(-1.5f, 1.0f, 1.5f);

//Right
glNormal3f(1.0f, 0.0f, 0.0f);
glNormal3f(1.0f, 0.0f, -1.0f);
glVertex3f(1.5f, -1.0f, -1.5f);
glNormal3f(1.0f, 0.0f, -1.0f);
glVertex3f(1.5f, 1.0f, -1.5f);
glNormal3f(1.0f, 0.0f, 1.0f);
glVertex3f(1.5f, 1.0f, 1.5f);
glNormal3f(1.0f, 0.0f, 1.0f);
glVertex3f(1.5f, -1.0f, 1.5f);

//Back
glNormal3f(0.0f, 0.0f, -1.0f);
glNormal3f(-1.0f, 0.0f, -1.0f);
glVertex3f(-1.5f, -1.0f, -1.5f);
glNormal3f(-1.0f, 0.0f, -1.0f);
glVertex3f(-1.5f, 1.0f, -1.5f);
glNormal3f(1.0f, 0.0f, -1.0f);
glVertex3f(1.5f, 1.0f, -1.5f);
glNormal3f(1.0f, 0.0f, -1.0f);
glVertex3f(1.5f, -1.0f, -1.5f);

//Left
glNormal3f(-1.0f, 0.0f, 0.0f);
glNormal3f(-1.0f, 0.0f, -1.0f);
glVertex3f(-1.5f, -1.0f, -1.5f);
glNormal3f(-1.0f, 0.0f, 1.0f);
glVertex3f(-1.5f, -1.0f, 1.5f);
glNormal3f(-1.0f, 0.0f, 1.0f);
glVertex3f(-1.5f, 1.0f, 1.5f);
glNormal3f(-1.0f, 0.0f, -1.0f);
glVertex3f(-1.5f, 1.0f, -1.5f);

glEnd();

glutSwapBuffers();
}

void update(int value) {
_angle += 1.5f;
if (_angle > 360) {
_angle -= 360;
}

glutPostRedisplay();
glutTimerFunc(25, update, 0);
}

int main(int argc, char** argv) {
//Initialize GLUT
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(400, 400);

//Create the window
glutCreateWindow("Lighting - videotutorialsrock.com");
initRendering();

//Set handler functions
glutDisplayFunc(drawScene);
glutKeyboardFunc(handleKeypress);
glutReshapeFunc(handleResize);

glutTimerFunc(25, update, 0); //Add a timer

glutMainLoop();
return 0;
}









Share this post


Link to post
Share on other sites
Quote:
Original post by Qureshi
can u tell me name of any good book on opengl ?


The OpenGL Programming Guide (AKA 'The Red Book') and The OpenGL Superbible are the ones which spring to mind.

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
      628391
    • Total Posts
      2982419
  • Similar Content

    • By test opty
      Hi all,
       
      I'm starting OpenGL using a tut on the Web. But at this point I would like to know the primitives needed for creating a window using OpenGL. So on Windows and using MS VS 2017, what is the simplest code required to render a window with the title of "First Rectangle", please?
       
       
    • 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.
  • Popular Now