glutDisplayFunc(); warning

Smjprogrammer

I get this warning in my OpenGl projects with my new compiler. I can fix the warning by putting void inside the OnDraw function call, but I am wondering if it is the wright thing to do. Is it?

---

Build started: Project: C, Configuration: Debug Win32

---

C.c
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(34): warning C4113: 'void (__cdecl *)()' differs in parameter lists from 'void (__cdecl *)(void)'
C.vcxproj -> C:\Users\Smjprogrammer\documents\visual studio 2013\Projects\C\Debug\C.exe
========== Build: 1 succeeded, 0 failed, 0 up-to-date, 0 skipped ==========

#include <glut.h>

void OnDraw()
{
	glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
	glBegin(GL_TRIANGLES);
	glColor3f(1, 0, 0);// Top Red.
	glVertex3f(0, 10, 0);

	glColor3f(0, 1, 0);// Bottom Left Green.
	glVertex3f(-10, -10, 0);

	glColor3f(0, 0, 1);// Bottom Right Blue.
	glVertex3f(10, -10, 0);
	glEnd();
	glutSwapBuffers();
}

void OnReshape(int w, int h)
{
	glViewport(0, 25, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(-12, 12, -12, 16, -1, 1);
	glMatrixMode(GL_MODELVIEW);
}

int main(int a, char **b)
{
	glutInit(&a, b);
	glutInitDisplayMode(GLUT_DEPTH | GLUT_RGBA | GLUT_DOUBLE);
	glutInitWindowSize(256, 256);
	glutCreateWindow("RGB Triangle");
	glutDisplayFunc(OnDraw);
	glutReshapeFunc(OnReshape);
	glutMainLoop();
}// RGB Triangle.

Ancient Dragon

In C there is a difference between foo() and foo(void). foo() is a function that takes an unspecified number of parameters or no parameters at all, while foo(void) is a function that takes no parameters. In c++ foo() and foo(void) are the same.

Smjprogrammer

So it should in fact be this.

#include <glut.h>

void OnDraw(void)
{
	glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
	glBegin(GL_TRIANGLES);
	glColor3f(1, 0, 0);// Top Red.
	glVertex3f(0, 10, 0);

	glColor3f(0, 1, 0);// Bottom Left Green.
	glVertex3f(-10, -10, 0);

	glColor3f(0, 0, 1);// Bottom Right Blue.
	glVertex3f(10, -10, 0);
	glEnd();
	glutSwapBuffers();
}

void OnReshape(int w, int h)
{
	glViewport(0, 25, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(-12, 12, -12, 16, -1, 1);
	glMatrixMode(GL_MODELVIEW);
}

int main(int a, char **b)
{
	glutInit(&a, b);
	glutInitDisplayMode(GLUT_DEPTH | GLUT_RGBA | GLUT_DOUBLE);
	glutInitWindowSize(256, 256);
	glutCreateWindow("RGB Triangle");
	glutDisplayFunc(OnDraw);
	glutReshapeFunc(OnReshape);
	glutMainLoop();
}// RGB Triangle.

Also if I am not mistaken there is a better way to program this with the new OpenGL standard. Is that standard included with this compiler?

Ancient Dragon

Visual C++ IDE/compiler knows nothing at all about OpenGL or it's standard. <glut.h> is not included in the standard compiler's installation.

Smjprogrammer

I know I had to put it there. Before it was there it seemed to already know something about OpenGL. Maybe it was the one file I did not have to put in the Windows folder.

Smjprogrammer

I know C does not have namespaces, but this program was originally in C++. I have no idea how to convert it since I did not write it.

---

Build started: Project: C, Configuration: Debug Win32

---

C.c
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(6): error C2061: syntax error : identifier 'Cube'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(6): error C2059: syntax error : ';'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(7): error C2449: found '{' at file scope (missing function header?)
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(36): error C2059: syntax error : '}'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(79): error C2065: 'display' : undeclared identifier
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(79): warning C4047: 'function' : 'void (__cdecl *)(void)' differs in levels of indirection from 'int'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(79): warning C4024: 'glutDisplayFunc' : different types for formal and actual parameter 1
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

#include <glut.h>
#include <math.h>

const int NUM_VERTICES = 8, NUM_FACES = 6;

namespace Cube
{
	int vertices[NUM_VERTICES][3] =
	{
		{ 0, 0, 0 }, { 0, 0, 1 }, { 0, 1, 0 }, { 0, 1, 1 },
		{ 1, 0, 0 }, { 1, 0, 1 }, { 1, 1, 0 }, { 1, 1, 1 }
	};
	int faces[NUM_FACES][4] =
	{
		{ 1, 5, 7, 3 }, { 5, 4, 6, 7 }, { 4, 0, 2, 6 },
		{ 3, 7, 6, 2 }, { 0, 1, 3, 2 }, { 0, 4, 5, 1 }
	};
	float vertexColors[NUM_VERTICES][3] =
	{
		{ 0.0, 0.0, 0.0 }, { 0.0, 0.0, 1.0 }, { 0.0, 1.0, 0.0 }, { 0.0, 1.0, 1.0 },
		{ 1.0, 0.0, 0.0 }, { 1.0, 0.0, 1.0 }, { 1.0, 1.0, 0.0 }, { 1.0, 1.0, 1.0 }
	};
	void draw()
	{
		glBegin(GL_QUADS);
		for (int i = 0; i < NUM_FACES; i++)
		{
			for (int j = 0; j <= 3; j++)
			{
				glColor3fv((float *)& vertexColors[faces[i][j]]);
				glVertex3iv((int *)& vertices[faces[i][j]]);
			}
		}
		glEnd();
	}
}

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT);
	Cube::draw();
	glFlush();
	glutSwapBuffers();
}

void timer(int v)
{
	static float u = 0.0;
	u += 0.01;
	glLoadIdentity();
	gluLookAt(8 * cos(u), 7 * cos(u) - 1, 4 * cos(u / 3) + 2, .5, .5, .5, cos(u), 1, 0);
	glutPostRedisplay();
	glutTimerFunc(1000 / 60.0, timer, v);
}

void reshape(int w, int h)
{
	glViewport(0, 0, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(60.0, (w) / (h), 0.5, 40.0);
	glMatrixMode(GL_MODELVIEW);
}

void init()
{
	glEnable(GL_CULL_FACE);
	glCullFace(GL_BACK);
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
	glutInitWindowSize(512, 512);
	glutCreateWindow("The RGB Cube");
	glutReshapeFunc(reshape);
	glutTimerFunc(100, timer, 0);
	glutDisplayFunc(display);
	init();
	glutMainLoop();
}// Animated Cube.

Ancient Dragon

did you try to just delete line 6?

Smjprogrammer

No. I had to do a little more then that after you gave me the idea, but yes that is pretty much what was needed.

#include <glut.h>
#include <math.h>

int vertices[8][3] =
{
	{ 0, 0, 0 }, { 0, 0, 1 }, { 0, 1, 0 }, { 0, 1, 1 },
	{ 1, 0, 0 }, { 1, 0, 1 }, { 1, 1, 0 }, { 1, 1, 1 }
};

int faces[6][4] =
{
	{ 1, 5, 7, 3 }, { 5, 4, 6, 7 }, { 4, 0, 2, 6 },
	{ 3, 7, 6, 2 }, { 0, 1, 3, 2 }, { 0, 4, 5, 1 }
};

float vertexColors[8][3] =
{
	{ 0.0, 0.0, 0.0 }, { 0.0, 0.0, 1.0 }, { 0.0, 1.0, 0.0 }, { 0.0, 1.0, 1.0 },
	{ 1.0, 0.0, 0.0 }, { 1.0, 0.0, 1.0 }, { 1.0, 1.0, 0.0 }, { 1.0, 1.0, 1.0 }
};

void draw()
{
	glBegin(GL_QUADS);
	for (int i = 0; i < 6; i++)
	{
		for (int j = 0; j <= 3; j++)
		{
			glColor3fv((float *)& vertexColors[faces[i][j]]);
			glVertex3iv((int *)& vertices[faces[i][j]]);
		}
	}
	glEnd();
}

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT);
	draw();
	glFlush();
	glutSwapBuffers();
}

void timer(int v)
{
	static float u = 0.0;
	u += 0.01;
	glLoadIdentity();
	gluLookAt(8 * cos(u), 7 * cos(u) - 1, 4 * cos(u / 3) + 2, .5, .5, .5, cos(u), 1, 0);
	glutPostRedisplay();
	glutTimerFunc(1000 / 60.0, timer, v);
}

void reshape(int w, int h)
{
	glViewport(0, 0, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(60.0, (w) / (h), 0.5, 40.0);
	glMatrixMode(GL_MODELVIEW);
}

void init()
{
	glEnable(GL_CULL_FACE);
	glCullFace(GL_BACK);
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
	glutInitWindowSize(512, 512);
	glutCreateWindow("The RGB Cube");
	glutReshapeFunc(reshape);
	glutTimerFunc(100, timer, 0);
	glutDisplayFunc(display);
	init();
	glutMainLoop();
}// Animated Cube.

Smjprogrammer

Well upon further looking through my saved things I found some OpenGL stuff with class's in them. I know how to get rid of them, but then how do I rewrite the constructor? I might also add I will not know what to do with the key word static either.

---

Build started: Project: C, Configuration: Debug Win32

---

C.c
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(4): error C2061: syntax error : identifier 'Moon'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(4): error C2059: syntax error : ';'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(5): error C2449: found '{' at file scope (missing function header?)
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(21): error C2059: syntax error : '}'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(25): error C2061: syntax error : identifier 'Orbiter'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(25): error C2059: syntax error : ';'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(26): error C2449: found '{' at file scope (missing function header?)
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(40): error C2059: syntax error : '}'
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(51): warning C4013: 'getPosition' undefined; assuming extern returning int
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(53): error C2065: 'moon' : undeclared identifier
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(53): error C2224: left of '.draw' must have struct/union type
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(60): warning C4013: 'advance' undefined; assuming extern returning int
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(80): error C2065: 'moon' : undeclared identifier
c:\users\smjprogrammer\documents\visual studio 2013\projects\c\c\c.c(80): error C2224: left of '.create' must have struct/union type
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

#include <glut.h>
#include <math.h>

class Moon
{
	int displayListId;
public:
	void create()
	{
		displayListId = glGenLists(1);
		glNewList(displayListId, GL_COMPILE);
		GLfloat direction[] = { -1.0, -1.0, -1.0, 0.0 };
		glLightfv(GL_LIGHT0, GL_POSITION, direction);
		glutSolidSphere(1.0, 25, 25);
		glEndList();
	}
	void draw()
	{
		glCallList(displayListId);
	}
};

static Moon moon;

class Orbiter
{
	double radius, u;
public:
	Orbiter(double radius) : radius(radius), u(0.0)
	{
	}
	void advance(double delta)
	{
		u += delta;
	}
	void getPosition(double &x, double &y, double &z)
	{
		x = radius * cos(u), y = 0, z = radius * sin(u);
	}
};

static Orbiter orbiter(5.0);

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadIdentity();
	double x, y, z;
	getPosition(x, y, z);
	gluLookAt(x, y, z, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
	moon.draw();
	glPopMatrix();
	glutSwapBuffers();
}

void timer(int v)
{
	advance(0.01);
	glutPostRedisplay();
	glutTimerFunc(1000 / 60, timer, v);
}

void reshape(int w, int h)
{
	glViewport(0, 0, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(40.0, (w) / (h), 1.0, 10.0);
}

void init()
{
	glEnable(GL_DEPTH_TEST);
	GLfloat yellow[] = { 1.0, 1.0, 0.5, 1.0 };
	glLightfv(GL_LIGHT0, GL_DIFFUSE, yellow);
	glEnable(GL_LIGHTING);
	glEnable(GL_LIGHT0);
	moon.create();
}

int main(int argc, char **argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowPosition(200, 200);
	glutInitWindowSize(256, 256);
	glutCreateWindow("The Moon");
	glutDisplayFunc(display);
	glutTimerFunc(100, timer, 0);
	glutReshapeFunc(reshape);
	init();
	glutMainLoop();
}// Moon Phase Simulator.

Ancient Dragon

Why are you trying to do this with C instead of C++??? You're just making it much more difficult than it needs to be for yourself.

Smjprogrammer

Most of the things I have in OpenGL are from online places. Since they are using C header files I figures they should be running as such.

Ancient Dragon

But the code you are having problems with is c++, not C. Don't you think you should be compiling c++ code as c++ and not C???

Smjprogrammer

Yeah I know it's weird, but I only have this one and one other OpenGL program like this. I just want them all to be in C.

Smjprogrammer

Is it even possible to convert that C++ish program to C?

Ancient Dragon

Yes, but not easily. First you will have to change Class Moon into a structure, move the class methods into simple global functions. Change the functions to accept a pointer to the struct Moon object that the function is to work with.

struct Moon
{

};

void createMoon(struct Moon* this)
{

}

void drawMoon(struct Moon* this)
{

}

Smjprogrammer

This is what I have so far, but do I really need to post the error to show you it is not going to work.

#include <glut.h>
#include <math.h>

struct Moon
{
	int displayListId;
};

void createMoon(struct Moon* this)
{
	displayListId = glGenLists(1);
	glNewList(displayListId, GL_COMPILE);
	GLfloat direction[] = { -1.0, -1.0, -1.0, 0.0 };
	glLightfv(GL_LIGHT0, GL_POSITION, direction);
	glutSolidSphere(1.0, 25, 25);
	glEndList();
}

void drawMoon(struct Moon* this)
{
	glCallList(displayListId);
}

static Moon moon;

class Orbiter
{
	double radius, u;
public:
	Orbiter(double radius) : radius(radius), u(0.0)
	{
	}
	void advance(double delta)
	{
		u += delta;
	}
	void getPosition(double &x, double &y, double &z)
	{
		x = radius * cos(u), y = 0, z = radius * sin(u);
	}
};

static Orbiter orbiter(5.0);

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadIdentity();
	double x, y, z;
	getPosition(x, y, z);
	gluLookAt(x, y, z, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
	moon.draw();
	glPopMatrix();
	glutSwapBuffers();
}

void timer(int v)
{
	advance(0.01);
	glutPostRedisplay();
	glutTimerFunc(1000 / 60, timer, v);
}

void reshape(int w, int h)
{
	glViewport(0, 0, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(40.0, (w) / (h), 1.0, 10.0);
}

void init()
{
	glEnable(GL_DEPTH_TEST);
	GLfloat yellow[] = { 1.0, 1.0, 0.5, 1.0 };
	glLightfv(GL_LIGHT0, GL_DIFFUSE, yellow);
	glEnable(GL_LIGHTING);
	glEnable(GL_LIGHT0);
	moon.create();
}

int main(int argc, char **argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowPosition(200, 200);
	glutInitWindowSize(256, 256);
	glutCreateWindow("The Moon");
	glutDisplayFunc(display);
	glutTimerFunc(100, timer, 0);
	glutReshapeFunc(reshape);
	init();
	glutMainLoop();
}// Moon Phase Simulator.

Smjprogrammer

Ok so I did not call the struct at all, but I can do that latter.

Ancient Dragon

You also have to make other changes, such as

Line 24: [icode]static struct Moon moon;[/icode]

line 54: [icode]drawMoon(&moon);[/icode]

line 81: [icode]createMoon(&moon);[/icode].

And make similar changes to class Orbiter.

Smjprogrammer

This is what I have so far. I got a little carried away with fixing the first problem you listed, and now I am a bit lost as to what I was doing.

#include <glut.h>
#include <math.h>

struct Moon
{
	int displayListId;
};

void createMoon(struct Moon* this)
{
	struct Moon a;
	a.displayListId = glGenLists(1);
	glNewList(a.displayListId, GL_COMPILE);
	GLfloat direction[] = { -1.0, -1.0, -1.0, 0.0 };
	glLightfv(GL_LIGHT0, GL_POSITION, direction);
	glutSolidSphere(1.0, 25, 25);
	glEndList();
}

void drawMoon(struct Moon* this)
{
	struct Moon a;
	glCallList(a.displayListId);
}

static struct Moon moon;

struct Orbiter
{
	double radius, u;
};

Orbiter(double radius) : radius(radius), u(0.0)
{
}

void advance(double delta)
{
	struct Orbiter a;
	a.u += delta;
}

void getPosition(double &x, double &y, double &z)
{
	struct Orbiter a;
	x = radius * cos(a.u), y = 0, z = radius * sin(a.u);
}

static struct Orbiter orbiter(5.0);

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadIdentity();
	double x, y, z;
	getPosition(x, y, z);
	gluLookAt(x, y, z, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
	draw();
	glPopMatrix();
	glutSwapBuffers();
}

void timer(int v)
{
	advance(0.01);
	glutPostRedisplay();
	glutTimerFunc(1000 / 60, timer, v);
}

void reshape(int w, int h)
{
	glViewport(0, 0, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(40.0, (w) / (h), 1.0, 10.0);
}

void init()
{
	glEnable(GL_DEPTH_TEST);
	GLfloat yellow[] = { 1.0, 1.0, 0.5, 1.0 };
	glLightfv(GL_LIGHT0, GL_DIFFUSE, yellow);
	glEnable(GL_LIGHTING);
	glEnable(GL_LIGHT0);
	create();
}

int main(int argc, char **argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowPosition(200, 200);
	glutInitWindowSize(256, 256);
	glutCreateWindow("The Moon");
	glutDisplayFunc(display);
	glutTimerFunc(100, timer, 0);
	glutReshapeFunc(reshape);
	init();
	glutMainLoop();
}// Moon Phase Simulator.

Ancient Dragon

lines 11 and 12: Why create another struct Moon object -- just use the one in the parameter to that function. Creating a second Moon object is pretty much useless.

Smjprogrammer

I don't know I did not write the code. I do know that if I take the original version written in C++ and take out line #12 I see nothing just a black screen. I don't know how to use the one in the parameter to that function. I don't even know what that means.

Ancient Dragon

In c++ each class method has a hidden parameter called this which is a pointer to an instance of the class. If you convert the c++ class to a c structure you need to make the class methods global variables and add the this pointer that is hidden and automatic in c++.

To to convert class method draw() to C format you need to make this change:

void drawMoon(struct Moon* this)
{
	glCallList(this->displayListId);
}

As I said several days ago converting that c++ code to C is possible, but will be tedious and time consuming. If you are not already well familiar with both languages you will have lot of difficulty. You can't just blindly make class methods global functions, you also have to think about and make some changes to the internals of how the methods go about doing things.

I'm not about to make all those changes for you or hold your hand while you do it. If you do not have the skills to make the changes on your own then you should think about not attempting to convert the c++ to C.

Smjprogrammer

Ok I will not convert them, but does anyone have anything I could study that would help me reach this goal myself?

Ancient Dragon

I know of nothing that will teach you how to convert c++ to c, it's just a simple matter of knowing both languages well so that you readily recognize the differences -- most of that is through many hours (years) of experience writing programs in both languages.

Smjprogrammer

I think I will take a brake from C and C++ for a while, and fiddle around with Visual Basic. I have been messing with it for a couple of days now. I figured why not it is in the Visual Studio plus it is something else to do. Maybe if I change things up I can learn a little faster. It's worth a try.

Ancient Dragon

Are you a member of DaniWeb.com? If not, you should be. They have very good support for languages such as vb.net. I'm not that good in vb.net either, haven't used it much.

Smjprogrammer

I am not a member of that. I am not even sure if it is vb.net or just vb that I am playing around with, but I have not had a whole lot of problems with it. It's not like I have been doing more then the Hello, world type stuff with it yet. Still don't even know if I like it or not. Sure is fun doing something new for a change. I will still do my usual stuff in C and C++, so as to not get rusty.

Ancient Dragon

If you are using Visual Studio 2010 or newer then you are using vb.net.

Go ahead and join DaniWeb -- ProgrammingForums.org is owned by DaniWeb.

Smjprogrammer

Can't I just use the forums here, or is there really going to be that big a difference.

Ancient Dragon

Yes, you can use forums here, but DaniWeb is a more active forum with over 1 million members. Don't be afraid to join other forums too.

Smjprogrammer

I am apart of some other forums. They just do not have anything to do with programming. PM me the code tags for Visual Basic.net for when I need them in the future.