Drivers & Software

[cryru]

Hey guys, I'm working on some OpenGL code and I noticed some peculiarities on one of my machines which don't happen on any of the other ones. After messing around with my code I managed to get it working but I have no idea why the changes I made caused it to work, and how to detect this other than hardcoding the renderer's name, so I decided to ask here.

GL_VERSION 4.5.13417

GL_RENDERER AMD Radeon HD 5700 Series

GLSL 440

I've also tested using a core, core and forward compat, compatibility and default OpenGL profile.

Here's what I'm doing each frame:

• I upload vertex data to a VertexBuffer using glMapBufferRange with GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT | GL_MAP_FLUSH_EXPLICIT_BIT
• I then flush the range of data which was mapped using glFlushMappedBufferRange
• I unmap the buffer
• One of the attributes of the vertex data is an int specifying the texture index within the shader.
• I bind and activate a series of textures, up to the number specified by MAX_TEXTURE_IMAGE_UNITS which on this driver is 18.
• In the fragment shader, I index a uniform array of samplers to determine which texture the vertex uses.
  • uniform sampler2D textures[TEXTURE_COUNT]

When performing this I get the result in the attached video. Random flickering, and sometimes the last texture being drawn is not displayed. I'd like to stress that I have checked the parameters that go into the functions stated below and have tested them on a variety of machines and GPUs including the Mesa3D llvmpipe, and therefore do not believe my ranges are wrong, but rather that I'm making a wrong assumption somewhere.

I got the scene to render properly by using only "GL_MAP_WRITE_BIT" and by limiting my activated textures (and uniform array size) to 1. The driver specifies that it supports both the GL_ARB_gpu_shader5 extension (which I've tried to request) and I'm using GLSL 440 therefore uniform indexing of opaque types should work. Additionally, I do not see why the invalidate buffer and flush explicit bits would cause problems either, considering the stated driver support.

I would greatly appreciate it if someone could shed some insight on this.

[elstaci]

You seem to be a developer using OpenGL coding. There is a specific AMD Forum where you can probably get better assistance from here: OpenGL & Vulkan‌ but you probably going to first have to post it here to get Whitelisted by one of the Moderators so that you have full access to these Developer's AMD Forums from here: https://community.amd.com/community/devgurus/newcomers-start-here

In OpenGL & Vulkan‌ there is one thread concerning OpenGL and RX 5700 series GPU Cards but several threads concerning OpenGL:

Good luck.

[cryru]

Thank you for the quick response. I'll post there, although I believe my question is more driver related.

Also, I'd like to clarify that I'm talking about the old AMD Radeon HD 5700 Series and not the new RX 5700.

[elstaci]

Oops, didn't catch that. The HD5700 is considered to be legacy and not supported by AMD Driver updates. you only have a choice of two drivers:

1- WHQL 2015

2-BETA 2016

You can download them from AMD download page from here: https://www.amd.com/en/support/graphics/amd-radeon-hd/ati-radeon-hd-5000-series/ati-radeon-hd-5750 -(Same driver for the HD5750. These are the only two shown at AMD Download page).

If your problem is a driver issue than you are out of luck since there are no more newer AMD Drivers for that HD5xxx series GPU Cards except those two mentioned above.

[cryru]

I figured the GPU is too old to receive driver updates, but I'd still like to know why it behaves in the way it does (if it's intended) and how to detect this behavior so I can work around it.

[elstaci]

Maybe someone in the Developer's Forum can answer your question or you can always open an Online AMD Service Request (Official AMD SUPPORT) from here: https://www.amd.com/en/support/contact-email-form 

[cryru]

Thanks for your help. I've posted on the developer forums.