2 Replies Latest reply on Jan 3, 2015 5:27 AM by xerophytic

    OpenGL tessellation issue

    xerophytic

      Hello,

       

      I had originally directed this to Intel's support department and was told to post here. I'm a developer writing OpenGL software. My issue is with the Intel HD 4600 GPU, though I suspect the issue will be found with all Intel GPUs. The Intel HD 4600 GPU produces unexpected results when omitting a tessellation control shader in the OpenGL rendering pipeline. The OpenGL spec allows control shaders to be omitted so long as the evaluation shader is present and GL_PATCH_DEFAULT_OUTER_LEVEL and GL_PATCH_INNER_LEVEL are specified. The aforementioned functionality is present and behaves as expected (according to the OpenGL spec) on the other GPUs I've tested with (NVIDIA and ATI), but the Intel GPU fails to produce appropriate vertices.

       

       

      This is reproducible by implementing any type of tessellation geometry without a control shader.
        • 1. Re: OpenGL tessellation issue
          joe_intel

          Hello xerophytic, what driver versions have you tested? Is there any version that produces good results?

          What operating systems, games or applications are affected?

          • 2. Re: OpenGL tessellation issue
            xerophytic

            Hello again,

             

            I've made some discoveries since my last post. For reference, my system had been running:

            • Windows 7 (64-bit)
            • Intel HD 4600 w/driver version 10.18.10.3907

             

            I wanted to make absolute certain that I was running the latest driver, so I ventured over to the download center and found that I had been running 15.36.3.64.3907 (10.18.10.3907). The latest driver is 15.36.7.64.3960 (10.18.10.3960). Here is where it gets interesting. The download page (https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=24348&lang=eng&ProdId=3720) for 15.36.7.64.3960 says, "This driver package contains version 15.36.3.64.3907 (10.18.10.3907) for Windows* 7/8/8.1." Which is incorrect. This is where I had tripped up. I knew that I was running 10.18.10.3907 (as reported by Windows) so when I checked the latest driver in the download center and looked at the driver version I was led to believe I was running the correct (latest) one. I was tipped off when I looked on my install drive and noticed the mismatch between the executable filenames for my installed driver and the latest in the download center.

             

            After installing the latest driver my initial issue is resolved.