使用鼠标在openGL中移动图形

Deadalus 发表于 Dev

Deadalus

我试图在按住鼠标左键的同时在openGL中移动图像。我不是要拖动对象，而只是移动整个图片。它是一个分形的2D图，有人告诉我可以使用gluortho2d，但找不到任何信息或类似的尝试来做。我假设像

void mouse_callback_func(int button, int state, int x, int y)
{
    if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    gluOrtho2D(x-250.0, x+250.0, y-250.0,y+250.);
glutPostRedisplay();
}

500x500的窗口，但无法正常工作。我离开的那一刻，窗口空白。有任何想法吗？

jozxyqk

gluOrtho2D修改当前矩阵。它设计用于与glMatrixMode(GL_PROJECTION)，例如：

glMatrixMode(GL_PROJECTION); //start editing the projection matrix
glLoadIdentity(); //remove current projection
gluOrtho2D(...); //create new one
glMatrixMode(GL_MODELVIEW); //back to editing the modelview matrix

设置相机概念可能更简单。

float cameraX, cameraY;
int lastMouseX, lastMouseY;

void mouse_callback_func(int button, int state, int x, int y)
{
    int dx = x - lastMouseX;
    int dy = y - lastMouseY;
    const float speed = 0.1f;
    if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    {
        cameraX += dx * speed; //or -=, depending on which direction feels more natural to you
        cameraY -= dy * speed; //-= as mouse origin is top left, so +y is moving down
        glutPostRedisplay();
    }
    lastMouseX = x;
    lastMouseX = y;
}

void display()
{
    glLoadIdentity(); //remove transforms from previous display() call
    glTranslatef(-cameraX, -cameraY, 0.0f); //move objects negative = move camera positive
    ...