glTranslatef()を使う場合と等価なglMultMatrixf()の使い方サンプル

gltest1.cpp

#ifdef WIN32
#include <SDKDDKVer.h>
#include <Windows.h>
#ifdef _DEBUG
#pragma comment(lib, "freeglutD.lib")
#else
#pragma comment(lib, "freeglut.lib")
#endif
#endif

#include <GL/GL.h>
#include <GL/freeglut.h>

void key_cb(unsigned char key, int x, int y)
{
	if (key == 27 || key == 'q') {
		glutLeaveMainLoop();
	}
}
void reshape_cb(int w, int h)
{
	glViewport (0, 0, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	if (w > h) {
		glOrtho(-(float)w/h, (float)w/h, -1.0f, 1.0f, -1.0f, 1.0f); 
	}
	else {
		glOrtho(-1.0f, 1.0f, -(float)h/w, (float)h/w, -1.0f, 1.0f); 
	}

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

void timer_cb (int value)
{
	glutTimerFunc(30, timer_cb, 0);
	glutPostRedisplay();
}

#define SET_IDENTITY_MATRIX(m) {                    \
	m[ 0]=1.0f; m[ 1]=0.0f; m[ 2]=0.0f; m[ 3]=0.0f; \
	m[ 4]=0.0f; m[ 5]=1.0f; m[ 6]=0.0f; m[ 7]=0.0f; \
	m[ 8]=0.0f; m[ 9]=0.0f; m[10]=1.0f; m[11]=0.0f; \
	m[12]=0.0f; m[13]=0.0f; m[14]=0.0f; m[15]=1.0f; \
}

void display_cb (void)
{
	glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glMatrixMode(GL_MODELVIEW);

	// using glTranslatef() 
	glPushMatrix();
	{
		glTranslatef(-0.6f, 0.0f, 0.0f);
		glutSolidTeapot(0.4);
	}
	glPopMatrix();

	//
	// glTranslatef(x, y, z) = | 1 0 0 0 |
	//                         | 0 1 0 0 |
	//                         | 0 0 1 0 |
	//                         | x y z 1 |
	glPushMatrix();
	{
		GLfloat mat[16];
		SET_IDENTITY_MATRIX(mat);
		mat[12] = 0.6f;           // x->mat[12], y->mat[13], z->mat[14]
		glMultMatrixf(mat);
		glutSolidTeapot(0.4);
	}
	glPopMatrix();

	glutSwapBuffers();
}

int main(int argc, char* argv[])
{
	glutInit(&argc, argv);
	glutInitWindowSize(640, 480);

	// GLUT settings
	glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);
	glutCreateWindow(argv[0]);
	glutKeyboardFunc(key_cb);
	glutDisplayFunc(display_cb);
	glutReshapeFunc(reshape_cb);
	glutTimerFunc(30, timer_cb, 0);

	// OpenGL settings
	glClearColor(0.0f, 0.0f, 0.3f, 1.0f);
	GLfloat light_diffuse[]   = {0.7f, 0.7f, 0.7f, 1.0f};
	GLfloat light_position[]  = {2.0f, 2.0f, 10.0f, 1.0f};
	glLightfv(GL_LIGHT0, GL_DIFFUSE,  light_diffuse);
	glLightfv(GL_LIGHT0 , GL_POSITION , light_position);
	glEnable(GL_LIGHT0);
	glEnable(GL_LIGHTING);

	glEnable(GL_DEPTH_TEST);
	glShadeModel(GL_SMOOTH);

	glutMainLoop();

	return 0;
}

マトリックスを使うと平行移動・回転・スケールを一度に保持できる点がうれしいかも？