Keeping the aspect ratio 종횡비 유지하기

It describes how to keep the aspect ratio.

OpenGL에서 종횡비를 유지하기 위해서는 Viewport와 Projection의 비율을 같게 해야 한다.

#include <gl/glut.h>
 
const int InitWidth = 300;
const int InitHeight = 300;
 
void MyDisplay();
void MyReshape(int NewWidth, int NewHeight);
 
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
 
    glutInitDisplayMode(GLUT_RGB);
    glutInitWindowSize(InitWidth, InitHeight);
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glutCreateWindow("OpenGL Aspect Ratio");
    
    glutReshapeFunc(MyReshape);
    // glutReshapeFunc sets the reshape callback for the current window.
    glutDisplayFunc(MyDisplay);
    
    glutMainLoop();
 
    return 0;
}
 
void MyDisplay() {
    glClear(GL_COLOR_BUFFER_BIT);
 
    glBegin(GL_TRIANGLES);
    glColor3f(0.0f, 0.0f, 1.0f);
    glVertex3f(0.0f, 0.5f, 0.0f);
    glColor3f(1.0f, 0.0f, 0.0f);
    glVertex3f(-0.5f, -0.5f, 0.0f);
    glColor3f(0.0f, 1.0f, 0.0f);
    glVertex3f(0.5f, -0.5f, 0.0f);
    glEnd();
 
    glFlush();
}
 
void MyReshape(int NewWidth, int NewHeight)
{
    glViewport(0, 0, NewWidth, NewHeight);
    // glViewport specifies the affine transformation of x and y from normalized device coordinates to window coordinates.
 
    GLfloat WidthFactor = (GLfloat)NewWidth / (GLfloat)InitWidth;
    GLfloat HeightFactor = (GLfloat)NewHeight / (GLfloat)InitHeight;
    
    glMatrixMode(GL_PROJECTION);    // glMatrixMode sets the current matrix mode.
    glLoadIdentity();    // glLoadIdentity replaces the current matrix with the identity matrix.
    glOrtho(-1.0 * WidthFactor, 1.0 * WidthFactor, -1.0 * HeightFactor, 1.0 * HeightFactor, -1.0, 1.0);
    // glOrtho describes a transformation that produces a parallel projection.
}

Run the program.

Resize the window.

Resize the window.