现代Opengl线点画问题

如何解决现代Opengl线点画问题

我正在尝试在OpenGL中实现Line Stipple，因为Line Stipple API已被弃用。它适用于直线和多边形，但不适用于圆形。以下着色器有问题吗？我看到线条和多边形的图案很好。但不适用于圈子。但是当我放大圆形时，我会看到图案。不知道是什么问题。请让我知道。

谢谢。

下面是我的顶点和片段着色器代码。

顶点着色器：

Header always set Content-Security-Policy "frame-ancestors https://*.mysite.com;"

片段着色器：

#version 420 core
layout (location = 0)in vec4 aPos;
flat out vec3 startPos;
out vec3 vertPos;
uniform mat4 mvp;
void main()
{
  vec4 pos  = mvp * vec4(aPos.x,aPos.y,0.0,1.0)
  gl_Position = pos;
  vertPos = pos.xyz/pos.w;
  startPos = vertPos;
}

下面是我设置统一值的代码。

#version 420 core
flat in vec3 startPos;
in vec3 vertPos;
uniform vec4 my_color;
uniform vec2 u_resolution;
uniform uint u_pattern;
uniform float u_factor; 
uniform int stipple; 
out vec4 color;
void main()
{
  if (stipple == 1) 
  { 
  vec2 dir = (vertPos.xy-startPos.xy) * u_resolution/2.0; 
  float dist = length(dir); 
  uint bit = uint(round(dist/u_factor)) & 15U; 
  if((u_pattern & (1U<<bit)) == 0U) 
    discard; 
  } 
  color = my_color;
}

然后绘制功能

if (vModel->getLineStipple() > 1 )
{
  glUniform1i(stip,1);

  GLint loc_res = glGetUniformLocation(shaderProgram,"u_resolution");
  GLint loc_pattern = glGetUniformLocation(shaderProgram,"u_pattern");
  GLint loc_factor = glGetUniformLocation(shaderProgram,"u_factor");

  GLushort pattern = vModel->getLineStipple(); 
  GLfloat factor = vModel->getStippleFactor();
  
  glUniform1ui(loc_pattern,pattern);
  glUniform1f(loc_factor,factor);
  glUniform2f(loc_res,_scrWidth,_scrHeight);
}
...