ios - gl_PointSize OpenGLES 说明

Question

在顶点着色器中设置 gl_PointSize = 1.0 意味着什么或达到什么目的？这是否意味着顶点本身就是一个像素？

Answer 1

What does setting gl_PointSize = 1.0 in vertex shader means or achieve? Does that mean the vertex itself is a pixel?

是的，确实如此。

参见 gl_PointSize :

The variable gl_PointSize is intended for a vertex shader to write the size of the point to be rasterized. It is measured in pixels.

参见 OpenGL ES Specification - Khronos OpenGL ES Registry, 3.3 Points, page 51 :

Point size is taken from the shader builtin gl_PointSize and clamped to the implementation-dependent point size range. If the value written to gl_PointSize is less than or equal to zero, results are undefined. The range is determined by the ALIASED_POINT_SIZE_RANGE and may be queried as described in chapter 6. The maximum point size supported must be at least one.
Point rasterization produces a fragment for each framebuffer pixel whose center lies inside a square centered at the point’s (xw, yw ), with side length equal to the point size.

这意味着，如果您定义 gl_PointSize = 1.0，则这指定了一个边长为 1 片段的正方形。中心点在这个正方形中的片段受到影响。

与“桌面”OpenGL 相比，在程序中不必启用点大小。 (在桌面 OpenGL 中，gl_PointSize 仅在启用 GL_PROGRAM_POINT_SIZE 时才有意义)。