带有iPhone的OpenGL ES 2.0:GL_POINT_SMOOTH在ES 2.0中绘制正方形，但可在ES 1.0中使用 [英] OpenGL ES 2.0 with iPhone: GL_POINT_SMOOTH draws squares with ES 2.0 but works in ES 1.0

问题描述

我正在尝试使用顶点缓冲区对象绘制圆，以在iPhone的OpenGL ES 2.0中启用GL_POINT_SMOOTH的情况下绘制点.

I'm trying to draw circles by using a Vertex Buffer Object to draw points with GL_POINT_SMOOTH enabled in OpenGL ES 2.0 on iPhone.

我已经使用以下ES 1.0渲染代码在iPhone 4上成功绘制了圆圈:

I've used the following ES 1.0 rendering code to draw circles successfully on iPhone 4:

glVertexPointer(2, GL_FLOAT, 0, circleVertices);
glEnableClientState(GL_VERTEX_ARRAY);
glEnable(GL_POINT_SMOOTH);
glPointSize(radius*2);
glDrawArrays(GL_POINTS, 0, 1);

我现在正在尝试通过设置VBO以及此ES 2.0渲染代码来实现相同的效果:

I'm now trying to achieve the same effect using a set-up VBO followed by this ES 2.0 rendering code:

glEnable(GL_BLEND); 
glEnable(GL_POINT_SPRITE_OES);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_POINT_SMOOTH);
glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);
glDrawElements(GL_POINTS, numPoints, GL_UNSIGNED_SHORT, BUFFER_OFFSET(0));

但是输出顶点非常明显是正方形，而不是圆形.

However the output vertices are very clearly square, not circular.

我已经尝试减少上述代码中的'glEnable'和相关调用，以模拟第一个工作版本，但是输出没有明显变化；形状仍然是正方形.我也尝试过将'glDrawElements'调用替换为:

I've tried reducing the 'glEnable' and related calls in the above to emulate the first, working version but no visible change in output occurs; the shapes are still square. I've also tried replacing the 'glDrawElements' call with:

    glDrawArrays(GL_POINTS,0,numPoints);

..但同样没有变化.

..but again there's no change.

在顶点着色器中设置了点大小，并且着色器已成功编译并运行:

The point size is set in the vertex shader, and the shader is successfully compiled and run:

uniform mediump mat4 projMx;

attribute vec2 a_position;      
attribute vec4 a_color;     
attribute float a_radius;       
varying vec4 v_color;
void main()
{
    vec4 position = vec4(a_position.x,a_position.y,1.0,1.0);
    gl_Position = projMx * position;
    gl_PointSize = a_radius*2.0;
    v_color = a_color;
}

有人知道为什么用glDrawElements VBO版本没有画圆吗?

Does anyone know why circles aren't drawn with the glDrawElements VBO version?

推荐答案

那是因为您启用了GL_POINT_SPRITE_OES，它用于绘制带有点的矩形，这对于广告牌很有用(比使用4个顶点绘制更简单，更快捷)一个矩形).

Thats becouse you enabled GL_POINT_SPRITE_OES, it is used to draw rectangles with a points, which is useful for billboards (it is simpler and faster than using 4 vertices to draw a rectangle).

尝试删除glEnable(GL_POINT_SPRITE_OES);而且应该可以.

Try removing glEnable(GL_POINT_SPRITE_OES); and it should work.

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