C ++/OpenGL-旋转矩形 [英] C++/OpenGL - Rotating a rectangle

问题描述

对于我的项目，我需要旋转一个矩形.我以为，这很容易，但是运行时却出现了无法预测的行为.

For my project i needed to rotate a rectangle. I thought, that would be easy but i'm getting an unpredictable behavior when running it..

这是代码:

    glPushMatrix();
    glRotatef(30.0f, 0.0f, 0.0f, 1.0f);
    glTranslatef(vec_vehicle_position_.x, vec_vehicle_position_.y, 0);
    glEnable(GL_TEXTURE_2D);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glBegin(GL_QUADS);

        glTexCoord2f(0.0f, 0.0f);
        glVertex2f(0, 0);
        glTexCoord2f(1.0f, 0.0f);
        glVertex2f(width_sprite_, 0);
        glTexCoord2f(1.0f, 1.0f);
        glVertex2f(width_sprite_, height_sprite_);
        glTexCoord2f(0.0f, 1.0f);
        glVertex2f(0, height_sprite_);

    glEnd();
    glDisable(GL_BLEND);
    glDisable(GL_TEXTURE_2D);
    glPopMatrix();

问题在于，我的矩形在旋转时正在窗口中的某个位置进行平移.换句话说，矩形不保持位置:vec_vehicle_position_.x和vec_vehicle_position_.y.

The problem with that, is that my rectangle is making a translation somewhere in the window while rotating. In other words, the rectangle doesn't keep the position : vec_vehicle_position_.x and vec_vehicle_position_.y.

出什么问题了?

谢谢

推荐答案

您需要翻转转换的顺序:

You need to flip the order of your transformations:

glRotatef(30.0f, 0.0f, 0.0f, 1.0f);
glTranslatef(vec_vehicle_position_.x, vec_vehicle_position_.y, 0);

成为

glTranslatef(vec_vehicle_position_.x, vec_vehicle_position_.y, 0);
glRotatef(30.0f, 0.0f, 0.0f, 1.0f);

这篇关于C ++/OpenGL-旋转矩形的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！