Mail Archives: cygwin/1999/08/22/15:32:23
I have been compiling programs that use opengl for some time, and I decided
to try out glut, but I am having a hard time getting even the simple sample
programs that came with glut to compile. I built the .def files into .a
libraries with dlltool just like the directions say, but when I try to
compile, they linker gives me lots of messages like :
(the command line is "gcc -o simple.exe simple.c -lglut32 -lopengl32")
undefined reference to _imp__glEnd
It creates a message like that for every gl* function the program uses, but
I'm wondering where the "_imp__" came from? The weird thing is that none of
the glut functions cause these errors, only the opengl ones. But when I
compile a program that uses only opengl, none of these messages occur.
The same thing also occurs with -lglut and -lopengl.
Here is the program in case it helps:
---begin simple.c---
/* Copyright (c) Mark J. Kilgard, 1996. */
/* This program is freely
distributable without licensing fees
and is provided without guarantee
or warrantee expressed or
implied. This program is -not- in the public
domain. */
/* This program is a response to a question posed by Gil
Colgate
<gcolgate AT sirius DOT com> about how lengthy a program is required
using
OpenGL compared to using Direct3D immediate mode to "draw a
triangle at screen coordinates 0,0, to 200,200 to 20,200, and I
want it
to be blue at the top vertex, red at the left vertex, and
green at the
right vertex". I'm not sure how long the Direct3D
program is; Gil has
used Direct3D and his guess is "about 3000
lines of code". */
/* X
compile line: cc -o simple simple.c -lglut -lGLU -lGL -lXmu -lXext -lX11
-lm */
#include <GL/glut.h>
void
reshape(int w, int h)
{
/* Because Gil
specified "screen coordinates" (presumably with an
upper-left origin),
this short bit of code sets up the coordinate
system to correspond to
actual window coodrinates. This code
wouldn't be required if you
chose a (more typical in 3D) abstract
coordinate system. */
glViewport(0, 0, w, h); /* Establish viewing area to cover entire
window. */
glMatrixMode(GL_PROJECTION); /* Start modifying the
projection matrix. */
glLoadIdentity(); /* Reset project
matrix. */
glOrtho(0, w, 0, h, -1, 1); /* Map abstract coords directly
to window coords. */
glScalef(1, -1, 1); /* Invert Y axis so
increasing Y goes down. */
glTranslatef(0, -h, 0); /* Shift origin
up to upper-left corner. */
}
void
display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_TRIANGLES);
glColor3f(0.0,
0.0, 1.0); /* blue */
glVertex2i(0, 0);
glColor3f(0.0, 1.0, 0.0);
/* green */
glVertex2i(200, 200);
glColor3f(1.0, 0.0, 0.0); /* red
*/
glVertex2i(20, 200);
glEnd();
glFlush(); /* Single buffered, so
needs a flush. */
}
int
main(int argc, char **argv)
{
glutInit(&argc,
argv);
glutCreateWindow("single triangle");
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMainLoop();
return 0; /* ANSI
C requires main to return int. */
}
---end simple.c---
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