將 2D Object 移動到 OpenGL 中的一個點

Question

如何使用 OpenGL 沿點（不是GL_POINTS ，而是坐標）的方向移動 2D object？

為了更好地理解我的代碼：

我已將大部分代碼拆分為不同的源代碼，但這是實際創建形狀和設置場景的源代碼：

void setupScene(int clearColor[]) {
    glClearColor(clearColor[0], clearColor[1], clearColor[2], clearColor[3]);
    //glClearColor(250, 250, 250, 1.0);  //  Set the cleared screen colour to black.
    glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);  // This sets up the viewport so that the coordinates (0, 0) are at the top left of the window.
    
    // Set up the orthographic projection so that coordinates (0, 0) are in the top left.
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, WINDOW_WIDTH, WINDOW_HEIGHT, 0, -10, 10);
    
    // Back to the modelview so we can draw stuff.
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear the screen and depth buffer.
}

void drawScene() {
    setupScene((int[]){250, 250, 250, 1});
    
    triangle(210, WINDOW_WIDTH, WINDOW_HEIGHT);
    
    glBegin(GL_QUADS);
    glColor3f(RGB(80), RGB(80), RGB(80));

    glPushMatrix();
    glTranslatef(400, 400, 0);
    glVertex2d(200, 100);
    glVertex2d(100, 100);
    glVertex2d(100, 200);
    glVertex2d(200, 200);
    glPopMatrix();
    glEnd();
    
    glutSwapBuffers();  // Send the scene to the screen.
}

void update(int value) {
    glutPostRedisplay();  // Tell GLUT that the display has changed.
    glutTimerFunc(25, update, 0);  // Tell GLUT to call update again in 25 milliseconds.
}

Answer 1

您需要翻譯模型視圖矩陣。 假設您已經處於模型視圖模式：

glPushMatrix();
glTranslatef(x, y, z);
// Draw your shape
glPopMatrix();

[編輯]

@paddy：這樣的東西？ 我試過了，但廣場沒動。 pastebin.com/2PCsy5kC

嘗試明確選擇模型視圖矩陣。 您的示例並未告訴我們當前處於哪種模式：

glSetMatrixMode(GL_MODELVIEW);
glPushMatrix();
glTranslatef(x, y, z);
// Draw your shape
glPopMatrix();

通常在渲染開始時重置所有內容......所以你進入GL_PROJECTION模式，調用glLoadIdentity()來重置它並設置你的相機，然后為GL_MODELVIEW矩陣做這個。

Answer 2

代表OP回答：

謝謝@paddy ，我試圖了解glTranslatef的用法並提供了解決方案。 這是工作代碼，它將創建一個 100x100 的正方形並將其移動到 400x200：

void setupScene(int clearColor[]) {
    glClearColor(clearColor[0], clearColor[1], clearColor[2], clearColor[3]);
    //glClearColor(250, 250, 250, 1.0);  //  Set the cleared screen colour to black.
    glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);  // This sets up the viewport so that the coordinates (0, 0) are at the top left of the window.
    
    // Set up the orthographic projection so that coordinates (0, 0) are in the top left.
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, WINDOW_WIDTH, WINDOW_HEIGHT, 0, -10, 10);
    
    // Back to the modelview so we can draw stuff.
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear the screen and depth buffer.
}

int a = 100;
int b = 200;
int x = 100;
int y = 100;

void drawScene() {
    setupScene((int[]){250, 250, 250, 1});
    
    triangle(210, WINDOW_WIDTH, WINDOW_HEIGHT);

    glPushMatrix();
    glTranslatef(x, y, 0);

    glBegin(GL_QUADS);
    glColor3f(RGB(80), RGB(80), RGB(80));

    glVertex2d(b, a);
    glVertex2d(a, a);
    glVertex2d(a, b);
    glVertex2d(b, b);

    glEnd();

    glPopMatrix();
    
    glutSwapBuffers();  // Send the scene to the screen.
}

void update(int value) {
    if (x != 400 && y != 200) {
        x += 4;
        y += 2;
    }
    glutPostRedisplay();  // Tell GLUT that the display has changed.
    glutTimerFunc(25, update, 0);  // Tell GLUT to call update again in 25 milliseconds.
}