如何在OpenGL ES 2.0中绘制反锯齿线? [英] How to draw anti aliased lines in OpenGL ES 2.0?

问题描述

我正在尝试绘制一些已存储为顶点数组的轮廓:

I am trying to draw some contours that I have stored as vertex arrays:

 typedef struct
{
    float* vertices;
    int nrPoints;
}VertexCurve;

list<VertexCurve> CurveList;

我正在使用opengl es 2.0书中的一些示例: http://opengles-book.com/

I am using some samples from an opengl es 2.0 book : http://opengles-book.com/

绘图方法如下:

    void Draw ( ESContext *esContext )
{
   UserData *userData = (UserData*)esContext->userData;

   // Set the viewport
   glViewport ( 0, 0, esContext->width, esContext->height );

   // Clear the color buffer
   glClear ( GL_COLOR_BUFFER_BIT );

   // Use the program object
   glUseProgram ( userData->programObject );

   //glEnable(GL_SAMPLE_ALPHA_TO_COVERAGE);
   //glEnable(GL_SAMPLE_COVERAGE);
   //glSampleCoverage(0.5, GL_FALSE);
   glEnableVertexAttribArray ( 0 );

   //glLineWidth(1);

   for (list<VertexCurve>::iterator it = CurveList.begin();
            it != CurveList.end(); it++)
   {
       // Load the vertex data
       glVertexAttribPointer ( 0, 3, GL_FLOAT, GL_FALSE, 0, (*it).vertices );

       glDrawArrays ( GL_LINE_LOOP, 0, (*it).nrPoints );
   }

   eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface );
}

另外，绘图的结果是:

我需要的是在OpenGL ES 2中具有更平滑的线条(抗锯齿)和我阅读的内容，可以通过多重采样来完成.从代码中可以看到，我尝试使用特定于此技术的一些方法，但是我无法完全理解它们的用法，并得到了不好的结果:

What i need is to have smoother lines (anti-aliased) and from what I read, in OpenGL ES 2 that can be done with multisampling. You can see from the code that I have tried using some methods specific to this technique but I was unable to fully understand their usage and got bad results:

如果有人可以向我解释如何获得抗锯齿的线条并使轮廓更平滑，我将不胜感激.

If someone can explain to me how to get anti-aliased lines and make the contours smoother, I will be very grateful.

推荐答案

可以使用令牌GL_MULTISAMPLE启用或禁用多重采样，默认情况下已启用.

Multisampling can be enabled or disabled using the token GL_MULTISAMPLE, and by default it is enabled.

为了确定当前活动的EGL曲面是否支持多重采样，请查询GL_SAMPLE_ BUFFERS的值:此处1表示支持，0表示不支持.然后GL_SAMPLES告诉每个像素存储了多少个样本.

In order to find out whether multisampling is supported by the currently active EGL surface, query the value of GL_SAMPLE_ BUFFERS: here 1 means supported, 0 indicates not supported. GL_SAMPLES then tells how many samples per pixel are stored.

所以我要做的就是在上下文属性列表中添加这两个属性:

So all I had to do was add those 2 attributes in the context attribute list :

    EGLint attribList[] =
   {
       EGL_RED_SIZE,       8,
       EGL_GREEN_SIZE,     8,
       EGL_BLUE_SIZE,      8,
       EGL_ALPHA_SIZE,     (flags & ES_WINDOW_ALPHA) ? 8 : EGL_DONT_CARE,
       EGL_DEPTH_SIZE,     (flags & ES_WINDOW_DEPTH) ? 8 : EGL_DONT_CARE,
       EGL_STENCIL_SIZE,   (flags & ES_WINDOW_STENCIL) ? 8 : EGL_DONT_CARE,
       EGL_SAMPLE_BUFFERS, (flags & ES_WINDOW_MULTISAMPLE) ? 1 : 0,
       EGL_SAMPLES, 4,
       EGL_NONE
   };

我将EGL_SAMPLE_BUFFERS设置为1以具有多重采样缓冲区，将EGL_SAMPLES设置为4，这样每个像素具有4个采样(FSAA x4).

I set EGL_SAMPLE_BUFFERS to 1 to have a multisample buffer and EGL_SAMPLES to 4 , in so having 4 samples per pixel (FSAA x4).

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