解释glOrtho（）的用法？ [英] Explain the usage of glOrtho()?

问题描述

我不明白glOrtho的用法。有人可以解释它的用途吗？

I can't understand the usage of glOrtho. can someone explain what is it used for ?

用于设置xy的范围z坐标限制

is it used to set the range of x y and z coordinates limit ?

glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);

这意味着x，y和z范围是从-1到1？

it means that the x, y and z range are from -1 to 1?

推荐答案

看看这张图片：图形投影

glOrtho 命令会生成一个底部两个面板。无论顶点在z方向有多远，它们都不会后退到距离。

The glOrtho command produces an "Oblique" projection that you see in the bottom two panels. No matter how far away vertexes are in the z direction, they will not recede into the distance.

每次我需要在OpenGL中做2D图形时使用glOrtho作为健康酒吧，菜单等）
每次窗口调整大小时使用以下代码：

I use glOrtho every time I need to do 2D graphics in OpenGL (such as health bars, menus etc) using the following code every time the window is resized:

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0f, windowWidth, windowHeight, 0.0f, 0.0f, 1.0f);

这会将OpenGL坐标重新映射到等效像素值（X从0到windowWidth和Y去从0到windowHeight）。注意，我已经翻转了Y值，因为OpenGL坐标从窗口的左下角开始。所以通过翻转，我得到一个更传统的（0,0）开始在窗口的左上角。

This will remap the OpenGL coordinates into the equivalent pixel values (X going from 0 to windowWidth and Y going from 0 to windowHeight). Note that I've flipped the Y values because OpenGL coordinates start from the bottom left corner of the window. So by flipping, I get a more conventional (0,0) starting at the top left corner of the window rather.

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