Re: [PyOpenGL-Users] Problem with glDepthMask

[Nicolas P. R. <Nic...@in...>]

Thanks for your question Ian ! While trying to make a screenshot I found the answer.

The rotating cube is displayed partially and it comes worse and worse, as if the depth buffer was not cleared.

And it is actually the case. I was not aware that the glClear takes the depth mask into account, meaning that:

gl.glDepthMask(gl.GL_FALSE)
gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT)

does not clear the depth buffer at all, while:

gl.glDepthMask(gl.GL_TRUE)
gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT)

works.


Nicolas


> On 20 Jan 2016, at 18:50, Ian Mallett <ia...@ge...> wrote:
> 
> On Wed, Jan 20, 2016 at 12:13 AM, Nicolas P. Rougier <Nic...@in...> wrote:
> I'm having a problem using the glDepthMask() function. I've made a simple example to show the problem:
> 
> https://gist.github.com/rougier/188c4771dab1694a074e
> ​This is a nice example.
> ​ 
> With the glDepthMask(True) / glDepthMask(False) commented out, the display is fine. But with them, the display is totally screwed. I would like to know if you get the same output or if this is only on my machine ?
> ​I'm having trouble running the sample, since "glut.glutInit()" fails:
> Traceback (most recent call last):
>   File "C:\Users\Ian Mallett\Desktop\glut-cube.py", line 127, in <module>
>     glut.glutInit()
>   File "C:\dev\Python33\lib\site-packages\OpenGL\GLUT\special.py", line 326, in glutInit
>     _base_glutInit( ctypes.byref(count), holder )
> TypeError: 'NoneType' object is not callable
> Mike, it was Python 3.3.0, PyOpenGL 3.1.0b2.
> 
> However, the code looks fine otherwise to me. Perhaps, can you clarify what "the display is totally screwed" means?
> 
> Ian
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