OpenGL Spinning Square

spinningsquare.c

// spinningsquare.c
// compiles on OSX with:
//     gcc spinningsquare.c -framework glut -framework opengl -o spinningsquare

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

static void init(void)
{
	glMatrixMode(GL_PROJECTION);
	glOrtho(0.0f, 10.0f, 0.0f, 10.0f, -1.0f, 1.0f);
	
	glMatrixMode(GL_MODELVIEW);
}

static float rotDeg = 0.0f;
static int lastTime = 0;

static void idle_func(void)
{
	int thisTime;
	
	thisTime = glutGet(GLUT_ELAPSED_TIME);
	rotDeg += (float)(thisTime - lastTime) * 0.1f;
	lastTime = thisTime;
	
	glutPostRedisplay();
}

static void render(void)
{
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

	glLoadIdentity();
	glTranslatef(5.0f, 5.0f, 0.0f);
	glRotatef(rotDeg, 0.0f, 0.0f, 1.0f);
	
	glColor3f(1.0f, 0.0f, 0.0f);
	glBegin(GL_TRIANGLES);
	{
		glVertex2f(-0.5f, -0.5f);
		glVertex2f(0.5f, -0.5f);
		glVertex2f(0.5f, 0.5f);
		
		glVertex2f(-0.5f, -0.5f);
		glVertex2f(0.5f, 0.5f);
		glVertex2f(-0.5f, 0.5f);
	}
	glEnd();

    glutSwapBuffers();
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
    glutInitWindowSize(400, 300);
    glutCreateWindow("Spinning Square");
    glutIdleFunc(&idle_func);
    glutDisplayFunc(&render);

	init();
    glutMainLoop();
    return 0;
}