iPhone OpenGL模板是作弊吗？

发布于 2024-09-04 11:12:48 字数 516 浏览 4 评论 0原文

XCode 的 OpenGL 模板似乎在解决这个“拉伸”视口问题，我在过去 3 个小时里一直试图理解这一问题。

在iphone“OpenGL ES应用程序”模板中，屏幕上上下弹跳的彩色正方形根本不是真正的正方形！

ES1Renderer.m（也是 ES2 文件）

static const GLfloat squareVertices[] = {
    -0.5f,  -0.33f,
     0.5f,  -0.33f,
    -0.5f,   0.33f,
     0.5f,   0.33f,
};

但由于非方形视口的拉伸/挤压效果，它在设备/模拟器上看起来是方形的。我尝试通过摆弄 glFrustumf() 来修复它，但这似乎并没有改变纵横比。

当我以 1:1 的宽度：高度提供 glViewport() 时，我能够得到看起来不错（未拉伸）的东西。但这似乎不是答案，因为它偏移了视口位置。

纠正这种拉伸的正确方法是什么？为什么 XCode 不这样做？

原文

XCode's OpenGL template seems to be cheating to solve this "stretched" viewport problem I've been trying to understand for the last 3 hours.

In the iphone "OpenGL ES Application" template, the colorful square that bounces up and down on the screen is not really a square at all!

ES1Renderer.m (the ES2 file as well)

static const GLfloat squareVertices[] = {
    -0.5f,  -0.33f,
     0.5f,  -0.33f,
    -0.5f,   0.33f,
     0.5f,   0.33f,
};

But it comes out looking square on the device/simulator due to the stretching/squashing effect of a non-square viewport. I tried to fix it by fiddling with glFrustumf() but that doesn't seem to change the aspect ratio.

I was able to get things looking good (not-stretched) when I fed glViewport() with a 1:1 widht:height.. But this doesn't seem like the answer because it offsets the viewport placement.

What's the right way to correct for this stretching and why doesn't XCode do it that way?

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怀念你的温柔 2024-09-11 11:12:48

我认为答案是：

XCode 是这样作弊的，以避免我们对设置视锥体所需的额外代码感到困惑。

这是我用来设置的代码，它修复了我遇到的挤压/拉伸问题：

const GLfloat zNear = 0.0001, zFar = 1000.0, fieldOfView = 45.0; 
GLfloat size;

size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0);

aspectRatio = (GLfloat) backingWidth / backingHeight;


glFrustumf(-size,//left
           size,//right
           (GLfloat)-size / aspectRatio,//bottom 
           (GLfloat)size / aspectRatio,//top 
           zNear,//zNear 
           zFar);//zFar     

glViewport(0, 0, backingWidth, backingHeight);

希望对某人有帮助。

I think the answer is:

XCode is cheating like this to avoid confusing us with the extra code required to setup a frustum.

Here's the code I'm using to set one up, and it fixed the squashing/stretching I was getting:

const GLfloat zNear = 0.0001, zFar = 1000.0, fieldOfView = 45.0; 
GLfloat size;

size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0);

aspectRatio = (GLfloat) backingWidth / backingHeight;


glFrustumf(-size,//left
           size,//right
           (GLfloat)-size / aspectRatio,//bottom 
           (GLfloat)size / aspectRatio,//top 
           zNear,//zNear 
           zFar);//zFar     

glViewport(0, 0, backingWidth, backingHeight);

Hope that helps someone.

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