重新定位形状/对象-OpenGL [英] Repositioning Shapes/Objects- OpenGL

问题描述

我想重新定位圆形，三角形，直线和圆弧.我该怎么办?我已经在网上搜索了解决方案，但没有找到专门解决该问题的方法.

I would like to reposition a circle, triangles, lines and an arc. How do I go about it? I've searched the web for solutions but nothing that address the issue specifically.

任何能引导我朝正确方向发展的信息都会有所帮助.

Any input that will lead me in the right direction will be helpful.

我正在将C ++与opengl一起使用.

I'm using C++ with opengl.

推荐答案

我想重新定位一个圆，三角形，直线和圆弧.

I would like to reposition a circle, triangles, lines and an arc.

那么您已经绘制了场景，现在想更改对象的位置吗?

So you already did draw the scene and now want to change the position of the objects?

那么，您需要了解的是，OpenGL不维护各种场景​​图.提交绘制调用后，事物仅在目标帧缓冲区上更新，仅此而已.你想改变一些东西吗?清除屏幕，重画所有内容，但现在应用调整.

Well then, all you need to understand is, that OpenGL doesn't maintain a scene graph of sorts. After submitting a draw call, things get only updates on the target framebuffer and that's it. You want to change something? Clear the screen, redraw everything, but now with the adjustments applied.

确实，OpenGL只是绘制东西，无非就是操作系统(视口/窗口)提供的某些纸张的复杂画笔(纹理)和铅笔(基元).

Really, OpenGL just draws things, it's nothing more than sophisticated brushes (textures) and pencils (primitives) for some paper offered by the operating system (viewport/window).

由于评论需要编辑

通常的带有动画的交互式OpenGL图形程序，是用命令式编程语言编写的，其结构是这样的(伪代码)

The usual interactive OpenGL graphics program with animations, programmed in a imperative programming language, is structured like this (pseudocode)

float T = 0
float alpha = 0, beta = 0
float red = 0, green = 0, blue = 0

paused = false

on_mousemove(mousemove):
    alpha += mousemove.rel_x
    beta  += mousemove.rel_y

on_keypress(keypress):
    switch keypress.key:
        case Key_ESCAPE:
            queue_event(Quit)
            return

        case Key_PAUSE:
            paused = not paused

        case Key_R:
            red += 0.1
        case Key_r:
            red -= 0.1

        case Key_G:
            green += 0.1
        case Key_g:
            green -= 0.1

        case Key_B:
            blue += 0.1
        case Key_b:
            blue -= 0.1

    queue_event(Redraw)

render()
    glViewport(0, 0, window.width, window.height)

    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    apply_projection()

    glMatrixMode(GL_MODELVIEW)
    glLoadIdentity()
    apply_modelview()

    glColor3f(red, green, blue)
    glRotatef(T * x_revolutions_per_second_factor, 1, 0, 0)
    glRotatef(alpha, 0, 1, 0)
    glRotate(beta, 0, 0, 1)

    draw_object()

    SwapBuffers()

main:
    initialize_libraries()
    load_resources()
    create_window_and_OpenGL_context()

    previous_loop = get_time()

    loop 'eventloop':
        event = peek_event()
        switch event.type:
            case MouseMove:
                on_mousemove(event.mousemove)

            case KeyPress:
                on_keypress(event.keypress)

            case Quit:
                break 'eventloop'

            case Redraw:
                render()
                break

            case NoEvents:
                fallthrough
            default:
                if not paused
                    render()

        current_loop = get_time()
        if not paused:
            T += current_loop - previous_loop
        previous_loop = current_loop

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