Window for OpenVR with Vulkan needed? - c++

When using vulkan and OpenVR for a game, do I need to create and open a window to make it work or can i just Submit the image to OpenVR?

Technically you only need to submit the frames to the OpenVR compositor but it is strongly recommends you also display those same frames in a window.
The overhead from doing so is minimal, you are literally just displaying the same textures to a window as well as in the HMD.

Related

A video player based on QtAV with Direct2D / OpenGL rendering

I'm developing a video player in Qt C++ using QtAV. QtAV uses ffmpeg internally. I need to show semi transparent overlays both my watermark logo and subtitles. I'm writing the application for windows. I use OpenAL library. OpenGL and Direct2D are the choice for renderers.
If I use OpenGL renderer, it works fine in some systems. The overlay works fine. But in some other systems the whole application will be just a black window. Nothing else I can see.
If I use Direct2D, the overlay wont work. And the renderer is a bit slow. But it works on all systems, without this overlays.
I have no code to show here because its not the coding issue. Even the examples in QtAV are not working. I need to find a way to show the overlays using Direct2D renderer OR find a solid way to use OpenGL rendering on all systems without fail.
Direct2D is not well supported in QtAV. So you may need to implement your own functions to add filters in your video render. That includes text draw functions, setting transparency etc.

SDL OpenGL Textures Lost

I have a fully working engine that is using SDL and OpenGL. I have a textured box on my OpenGL/SDL screen - however when I try to change the video mode (e.g. toggle fullscreen with F11) the texturing is lost (the box is just plain white), if I toggle back to windowed mode the box is still white (with the textured image lost). Does this mean I cannot change my video mode in the middle of the application (e.g. toggle fullscreen) or does it mean I have to reload my OGL textures every time I do so?
Some extra notes: I am using CodeBlocks with MinGW on windows 7, the libraries I have linked are: SOIL (a library for easily loading textures in OGL - http://www.lonesock.net/soil.html), OpenGL32, Glu32 and SDL.
I have some images to demonstrate my problem (the first one is windowed mode and the second one is when I try to change to fullscreen with a call to SDL_SetVideoMode(...) - SDL_WM_ToggleFullScreen doesn't work.
I have a textured box on my OpenGL/SDL screen - however when I try to change the video mode (e.g. toggle fullscreen with F11) the texturing is lost (the box is just plain white), if I toggle back to windowed mode the box is still white (with the textured image lost). Does this mean I cannot change my video mode in the middle of the application (e.g. toggle fullscreen) or does it mean I have to reload my OGL textures every time I do so?
It strongly depends on how the used framework implements video mode changes.
In general when deleting an OpenGL context all it's associated data is lost, except if there's another OpenGL context with which a "sharing" has been established. That can be used to keep all uploaded data persistent between context recreation. However a mere video mode change usually doesn't require a context recreation, and usually also not a window recreation.
However the framework used by you (SDL) will completely clean up a window and the context when changing the video mode, thus loosing you the loaded resources. Unstable development versions of SDL have better OpenGL support, allowing for video mode changes without context teardown inbetween.
Unfortunately, the problem stems from the way SDL recreates the window. I had this problem before and the solution for me was to set up a special uninitialize and initialize function that only got rid of/created images.
Essentially, when SDL's Resize event is called (http://www.libsdl.org/docs/html/sdlresizeevent.html) you would uninitialize any artistic assets required and then re-initialize them after entering or leaving fullscreen.

SDL window management with OpenGL and DirectX

I'm porting a small graphics engine from DirectX 9 to OpenGL. The engine uses SDL (now ported to 2.0) to manage input and window creation.
I want to know how to correctly handle window events for both OpenGL and DirectX. I'm interested in these for Desktop platforms (linux, OSX and windows)
Window resolution change
Full screen to windowed / windowed to fullscreen handling
Alt+tab handling -
I've tried to search through the net but information is quite not focused in one place. I imagine many others faced the same problem before.
Are there any resources to read guidelines on that kind of handling for my engine?
Is it possible to handle resolution change without losing transfered resources to the renderer system in both OpenGL and DirectX?
Window resolution change
OpenGL itself requires no special treatment for this. Unfortunately SDL goes through a full window reinitialization, including the OpenGL context on a window size change, which means, that all OpenGL state objects (that is, textures, vertex buffers, shaders and so on) are lost.
This is however a limitation of SDL.
Personally I thus prefer GLFW for creating a OpenGL window and context. You can still use SDL for other things though (like audio, networking, image loading and such).
Full screen to windowed / windowed to fullscreen handling
The is effectively a window size change as well. See above.
Alt+tab handling -
OpenGL requires no special effort for this. Just minimize the window when Alt+Tab-ing out and stop the game loop. When the window gets restored just continue the game loop.

Creating a program that creates a full screen overlay

I want to write a program that would create a transparent overlay filling the entire screen in Windows 7, preferably with C++ and OpenGL. Though, if there is an API written in another language that makes this super easy, I would be more than willing to use that too. In general, I assume I would have to be able to read the pixels that are already on the screen somehow.
Using the same method screen capture software uses to get the pixels from the screen and then redrawing them would work initially, but the problem would then be if the screen updates. My program would then have to minimize/close and reappear in order for me to be able to read the underlying pixels.
Windows Vista introduced a new flag into the PIXELFORMATDESCRIPTOR: PFD_SUPPORT_COMPOSITION. If the OpenGL context is created with an alpha channel, i.e. AlphaBits of the PFD is nonzero, the alpha channel of the OpenGL framebuffer is respected by the Windows compositor.
Then by creating a full screen, borderless, undecorated window you get this exakt kind of overlay you desire. However this window will still receive all input events, so you'll have to do some grunt work and pass on all input events to the underlying windows manually.

Screen capture of MDI app with OpenGL graphics using MFC

In our MDI application - which is written in MFC - we have a function to save a screenshot of the MDI client area to file. We are currently doing a BitBlt from the screen into a bitmap, which is then saved. The problem is that some of the MDI child windows have their content rendered by OpenGL, and in the destination bitmap these areas show up as blank or garbled.
I have considered some alternatives:
- Extract the OpenGL content directly (using glReadPixels), and draw this to the relevant portions of the screen bitmap.
- Simulate an ALT+PrtScr, since doing this manually seems to get the content just fine. This will trash the clipboard content, though.
- Try working with the DWM. Appart from Vista and Win7, this also needs to work on Win2000 and XP, so this probably isn't the way to go.
Any input will be appreciated!
The best way to get a bitmap from an OpenGL window is to draw the content to a bitmap 'window'. See PFD_DRAW_TO_BITMAP for more information on how to do this.
If you want to go with the Alt+PrtScr way, you have to consider that many users have their own print screen tool installed which reacts on that very same hotkey. So you can't be sure that this hotkey will copy the content to the clipboard. It may just open the window of the installed print screen tool/utility.
Use the glReadPixels() approach. This question is asked quite often, here, on the gamedev.net forums and on other places, so google should show you code samples easily, but the glReadPixels() approach is the generally recommended approach.
Simulating keypresses is a recipe for disaster, I would stay away from that.