I display a 2D texture in OpenGL using Qt.
Unfortunately I have found out that I need to support running my application via Remote Desktop to a Windows 7 PC. In this case I need to use OpenGL ES 2.0 API (ANGLE).
Due to low bandwidth my 2D visualization seems to be lagging.
My texture may have higher resolution than the screen so that it needs to be minified.
When not using remote desktop my approach have been to specify a very detailed texture and let the graphics card do the minification.
However now I am thinking that the OpenGL calls are executed in software locally and not on the remote machine? In which case the textures have to be transmitted via TCP/IP?
Does this mean that I should do minification myself before using the textures?
As an example instead of using a 2048x2048 texture I may bin 2x2 pixels in C++ and upload a 1024x1024 texture.
Alternatively I could use glGenerateMipmap?
I feel multiple terms are confused here: RDP just transfers the entire remote desktop for you whatever is on it, so no "OpenGL calls are executed in software locally". Hence, unfortunately it will not help if you reduce the texture size in your app, even if you remove it entirely (try it). RDP is not really suitable for real time animation.
Your app better be running locally on the user machine, so better to think how to distribute your OGL app to users.
If you cannot install your app on users machine, or give them installation kit, then
maybe turning your app to a browser app is a better option.
WebGL there for exactly this kind of applications, and is a standard too:
https://www.khronos.org/webgl/
Related
I have a server with nvidia graphics card, and I want to run some openGL applications and xforwarding the display to client.
How can I achieve this? Currently I have not installed X window System yet.
X forwarding means, that all rendering commands are encapsulated into the X transport and transferred over to the machine with the display and executed there. The upside is, that the remote end does not require a GPU whatsoever. The downside is, that it consumes (well, rather gobbles up) lots of network bandwidth.
OpenGL up to version 2.1 specifies GLX opcodes for the X11 transport, so is network transparent. And if you make liberal use of display lists and keep the amount of data transferred small (i.e. no client side vertex array, only a few and little textures), OpenGL-over-GLX-over-X11-over-TCP works rather fine.
However these days it's more efficient to render remotely and only transfer the generated image using a high efficiency compression codec. Plain X11 forwarding can't do that, though. But you can do it using Xpra backed by a "true" X server, talking to an actual GPU. The problem is, that you'll need that particular X server to occupy the GPU.
A better method is, to detect if there's the GLX extension available, and if not if there's a GPU around and use that to render into a XSHM pixmap. That way also Xpra on a virtual framebuffer server will work. Unfortunately doing the later with OpenGL is annoyingly difficult to implement in a way, that it works transparently accross context creation APIs. It can be done (BT;DT) but actually for this kind of thing I actually prefer Vulkan, because despite Vulkan's verbosity it takes less work to do reliably with Vulkan than with OpenGL.
Maybe (unlikely) we'll see some X11 extension for compressed transfer of pixmaps, some high compression XV or similar. That, in combination with an pure off-screen, GPU rendering (we already have that), would make for a far more efficient system.
This should be straightforward, but for some reason I can't make it work.
I hired a Softlayer Bare Metal Server that comes with an Nvidea Tesla GPU.
I'm remotley executing a program (openScad) that needs OpenGL > 2.0 in order to properly export a PNG file.
When I invoke openScad and export a model, I get a 0kb png file as output, a clear symptom that OpenGL > 2.0 support is not present.
In order to make sure that I was running openGL > 2.0 I connected to my server via RD and ran GlView. To my surprise I saw that the server was supporting nothing but openGL 1.1.
After a little research I found out that for standard RD sessions the GPU is not used so it makes sense that I'm only seeing openGL 1.1.
The problem is that when I execute openscad remotley, it seems that the GPU is not used either.
What can I do to successfully make the GPU capabilities of my server work when I invoke openscad remotely?
PS: I checked with softlayer support and they are not taking any responsibility
Most (currently all) OpenGL implementations that use a GPU assume that there's a display system of some sort using that GPU; in the case of Windows that would be GDI. However on a headless server Windows usually doesn't start the GDI on the GPU but uses some framebuffer.
The NVidia Tesla GPUs are marketed as compute-only-devices and hence their driver does not support any graphics functionality (note that this is a marketing limitation implemented in software, as the silicon is perfectly capable of doing graphics). Or in other words: If you can implement your graphics operations using CUDA or OpenCL, then you can use it to generate pictures. Otherwise (i.e. for OpenGL or Direct3D) it's useless.
Note that NVidia is marketing their "GRID" products for remote/cloud rendering.
I'm replying because i faced a similar problem in the past; also trying to run an application that needed openGL 4 on a windows server.
windows remote desktop indeed doesn't trigger opengl. However if you use tigervnc instead and then start your openScad application it might recognize your opengl drivers. At least this trick did it for me.
(when opening an openGL context in a program it scan's for monitors/RD's attached i pressume).
hope it helps.
I want to implement an opengl application which generates images and I view the image via a webpage.
the application is intended to run on a linux server which has no display, no x windows, but with gpu.
I know that egl can use pixmap or pbuffer as render targets.
but the function eglGetDisplay worries me, it sounds like I still need to have attached display to make it work?
does egl work without display and xwindows or wayland?
This is a recurring question. TL;DR: With the current Linux graphics driver model it is impossible to use the GPU with traditional drivers without running a X server. If the GPU is supported by KMS+DRM+DRI you can do it. (EDIT:) Also in 2016 Nvidia finally introduced truly headless OpenGL support in their drivers through EGL.
The long story is, that technically GPUs are perfectly capable of rendering to an offscreen buffer without a display being attached or a graphics server running. However due to the history of graphics driver and environment development this is not possible, yet has not been possible for a long time. The assumption back then (when graphics was first introduced to Linux) was: "The graphics device is there to deliver a picture to a screen." That a graphics card could be used as an accelerating coprocessor was not even a figment of an idea.
Add to this, that until a few years ago, the Linux kernel itself had no idea how to talk to graphics devices (other than a dumb framebuffer somewhere in the system's address space). The X server was what talked to GPUs, so you needed that to run. And the first X server developers made the assumption that there is a person between keyboard and chair.
So what are your options:
Short term, if you're using a NVidia GPU: Just start an X server. You don't need a full blown desktop environment. You can even save yourself the trouble of starting a window manager. Just have the X server claim the VT and being active. There is now support for headless OpenGL contexts through EGL in the Nvidia drivers.
If you're using an AMD or Intel GPU you can talk directly to it. Either through EGL or using KMS (Google for something called kmscube, when trying it, make sure you switch away from your X server to a text VT first, otherwise you'll crash the X server). I've not tried it yet, but it should be possible to adjust the kmscube example that it uses the GPU to render into an offscreen buffer, without switching the VT to graphics mode or have any graphics output on the display framebuffer at all.
As datenwolf told u can create a frame buffer without using x with AMD and intel GPU. since iam using AMD graphics card with EGL and iam able to create a frame buffer and iam drawing on it.with Mesa Library by configuring without x u can achieve.
I'm trying to develop an Apache2 module that utilizes OpenGL to perform off-screen rendering and dynamically generate images that I can then send back to the client.
Apache2 is running on an Ubuntu 12.04 machine and I created a test module that renders a quad and stores the frame as an image to disk using OpenGL/GLX. But when the module receives a client request, it crashes at XOpenDisplay(0) with a segmentation fault. Any ideas what could be going wrong?
Edit:
All the examples I have seen talk about using a pixel buffer (PBuffer). As far as I know, these are deprecated and FBOs should be used instead. Can someone explain how to create a context and use FBOs to perform off-screen rendering?
While technically it's perfectly possible to do windowless, display server less off-screen GPU accelerated rendering with OpenGL, practically it's impossible these days because you need a display environment to actually get access to the GPU. Fortunately the structure of graphics systems is changing these days (Hybrid graphics, display compositors). Already Mesa provides an off-screen context creation mode (OSMesa), but it's far from being feature complete.
So right now, you'll need some kind of display server drawable to work with on which you can bind a context. X11 offers two kinds of GPU accelerated drawables: Windows and PBuffers. You can use FBOs with either (PBuffers are technically Windows that can not be mapped to the root window and have an off-screen canvas). The easiest way to go is to create a regular window on an X server but not showing it; you can still create an OpenGL context on it and create FBOs, like shown in numerous tutorials. But for OpenGL to work the X server you use must be active hold the console and be configured to use the GPU (theoretically with newer Hybrid graphics capable X servers and drivers it should be possible to configure the X server to use a dummy display device and configure the GPU as a secondary device for accelerated rendering, but I never tried that, so far).
The situation is as follows:
There is a remote Linux server (no GUI), which builds the OpenGL scene.
Objective: Transfer generated image(s) to client windows machine
I can not understand some thing with offscreen rendering, read a lot of literature, but still not well understood:
Using GLUT implies setting variable DISPLAY. If I right understand means remote rendering via x11. If I run x11 server on windows (XWin server) machine everything works. If I try to run without rendering server , then : freeglut (. / WFWorkspace): failed to open display 'localhost: 11.0'. Anyway x11 is not suitable.
Do I need to create a graphics context (hardware rendering support is required)?
How can I create a graphics context on Linux server without GLUT/x11?
Framebuffer object - whether it is suitable for my task and whether the graphics context is necessary for it?
What is the most efficient way to solve this problem (rendering requires hardware support).
Not an important issue, but nevertheless:
Pixel buffer object. I plan to use it to increase the read performance of GPU memory. Is it profitable within my task?
You need to modify your program to use OSMesa - it's a "null display" driver used by Mesa for software rendering. Consider this answer for near duplicate question as a starter:
https://stackoverflow.com/a/8442800/2702398
For a full example, you can check out the examples in the Mesa distribution itself, such as this: http://cgit.freedesktop.org/mesa/demos/tree/src/osdemos/osdemo.c
Update
It appears that VirtualGL (http://www.virtualgl.org) supports remote rendering of OpenGL/GLX protocol and serves rendered pixmaps to the client over VNC (whereupon, VNC head can be trivially made virtual).
If you want to use full OpenGL spec, use X11 to create context. Here is a tutorial showing how you can do this:
http://arrayfire.com/remote-off-screen-rendering-with-opengl/