I'm trying to draw point sprites in a small Mac app. I want each sprite to have its own size, and I know that OpenGL ES has the client state "GL_POINT_SIZE_ARRAY_OES".
I did some googling and discovered that there is a similar value "GL_POINT_SIZE_ARRAY_APPLE" which (you'd think) should do the same thing. For some reason, though, it doesn't seem to. Here's my drawing code:
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_POINT_SIZE_ARRAY_APPLE);
glVertexPointer(2, GL_FLOAT, sizeof(SpriteData), spriteVertices);
glPointSizePointerAPPLE(GL_FLOAT, sizeof(SpriteData), spriteVertices + sizeof(LocationF));
glDrawArrays(GL_POINTS, 0, spriteCount);
glDisableClientState(GL_POINT_SIZE_ARRAY_APPLE);
glDisableClientState(GL_VERTEX_ARRAY);
SpriteData is a struct containing the vertex/size data of each sprite. spriteVertices is just an interleaved array of that struct.
The vertex pointer is working fine; it's drawing the sprites, but seems to be ignoring their size values. It instead defaults to the value set by glPointSize().
Despite the fact that this code compiles with no warnings, it seems very suspicious to me that googling "GL_POINT_SIZE_ARRAY_APPLE" brings up almost no results. Is this a useless parameter? If so, how else can I achieve what I want?
There is no official OpenGL extension which exposes a GL_POINT_SIZE_ARRAY_APPLE extension. This may be some detritus in Apple's headers, but you shouldn't use it. Just use a generic vertex array and use the value you pass as a point size.
If you want cross-platform code, you should avoid system-dependent headers. Instead, use a proper OpenGL loader, which comes with cross-platform headers that won't have system-dependent, non-standard detritus in them.
Related
As per my need I want to redraw only some part of the scene for each frame instead
of redrawing the entire scene only if some portion of it is updated.
Is there a way to do that in OpenGL ES 2.0?
Please any input on this will be really helpful
OpenGL does not really support incremental rendering. You need to draw the entire frame every time you are asked to redraw.
The closest I can think of is that you render your static data to an offscreen framebuffer, using a FBO (Frame Buffer Object). You should be able to find plenty of examples online and in books if you look for keywords like "OpenGL FBO". You will be using calls like glGenFramebuffers(), glBindFramebuffer(), glFramebufferTexture2D(), etc.
Once you rendered the static content into an FBO, you can copy it to the default framebuffer at the start of each redraw, and then render the dynamic content on top of it. This can be a worthwhile method if rendering the static content is very expensive. Otherwise, doing the copy from FBO to default framebuffer can be more expensive than simply re-rendering the static content each time.
The above is pretty easy if the static content is in the background, and the dynamic content is completely in front of it. If static and dynamic content overlap, it gets trickier. You will then have to restore the depth buffer resulting from rendering the static content each time before starting to render the dynamic content. I can't think of a good way to do that in ES 2.0. The features to do this relatively smoothly (depth textures, glBlitFramebuffer) are only in ES 3.0 and later.
There is one other option that I don't think is very appealing, but I wanted to mention it for completeness sake: EGL defines a EGL_SWAP_BEHAVIOR attribute that can be set to EGL_BUFFER_PRESERVED. One big caveat is that it's optional, and not supported on all devices. It also only preserves the color buffer, and not auxiliary buffers, like the depth buffer. If you want to read up on it anyway, see eglSwapBuffers and eglSurfaceAttrib.
I need to blend a few image together into a single one, pretty much as what's described here: OpenGL - mask with multiple textures.
I used the solution that is proposed there, but there's an issues with the glBlendFuncSeparate method.
Turns out that this method was introduced in later openGL versions, and according to my gl.h file the version I'm using is 1.
After much searching and reading I realized that this is what I have to work with and that I can't just upgrade my openGL version.
I went ahead and downloaded GLEW.
I added glew.h and glew.c into my VS10 project, defined GLEW_BUILD and now it finally compiles without complaining about glBlendFuncSeparate, but when I run the program it crashes when it tries to call the method, saying Access Violation, I guess that it points to NULL and then crashes when that's being run.
I continued reading and searching on this, and from what I understand, I need to use OpenGl Extensions to make it work.
If what's written in Using OpenGL extensions On Windows is correct then I'm missing something.
Let's say I do everything it says, I "download and install the latest drivers and SDKs for your graphics card" and then compile it, even if it runs on my machine, I see no guarantee that it won't crash on someone else's machine, since they might not have done the same.
I have two questions:
Am I missing something here? this whole process seems way too complicated, and environment dependent.
Is there an alternative for using glBlendFuncSeparate in this kind of a scenario?
You don't need glBlendFuncSeparate(GL_ZERO, GL_ONE, GL_SRC_COLOR, GL_ZERO); to use trick described in OpenGL - mask with multiple textures. Yes, you can't added color directly to alpha channel, like described in previous example, but you can be little tricky.
During writing your mask just disable writting all color channels, except alpha:
glColorMask(false, false, false, true);
and enable multiplying mask's alpha on background alpha-channel:
glBelndFunc(GL_ZERO, GL_SRC_ALPHA);
After writing bitmask, don't forget setup your glColorMask back.
glColorMask(true, true, true, true);
//-----------------------------------------------------------------------------------------------------------------------
And yes, you need mask with information in alpha channel:
1) It's can be done with GIMP (very simple, but required GIMP knowlege).
2) You can write you own rootine, for pushing color information to alpha channel, before mask texture creation (it's very simple - just few lines of code).
3) Or just use GL_ALPHA "format" attribute in glTexImage2D for mask texture. This flag just writes bitmaps color to texture alpha channel.
I followed this post to play with OpenGL (programmable pipeline) on Ruby
Basically, I'm just trying to create a blue window, and here's the code.
Ray::GL.major_version = 3
Ray::GL.minor_version = 2
Ray::GL.core_profile = true # if you want/need one
window = Ray::Window.new("Test Window", [800, 600])
window.make_current
glClearColor(0, 0, 1, 1);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
Instead, I got a white window created. This indicated that I was missing something, but I couldn't figure out what I was missing as the resources for OpenGL on Ruby seemed limited. I have been searching all over the web, but all I found was fixed-pipeline OpenGL stuff for Ruby.
Yes, I could use Ray's built-in functions to set the background color and draw stuff, but I didn't want to do that. I just wanted to use Ray to setup the window, then called OpenGL APIs directly. However, I couldn't figure out what I was missing in the code above.
I would greatly appreciate any hint or pointer to this (maybe I needed to swap the buffer? but then I didn't know how to do it with Ray). Is there any body familiar with using Ray that can give me some hints on this?
Or, are there any other tools that would allow me to setup OpenGL binding (for none fixed-pipeline)?
It would appear that you set the clear color to be blue, then cleared the back buffer to make it blue. But, as you said, you have not swapped the buffers to put the back buffer onto your screen. As far as swapping buffers goes, here's another answer from stack overflow
"Swapping the front and back buffer of a double buffered window is a function provided by the underlying graphics system, i.e. Win32 GDI, or X11 GLX. The function's you're looking for are wglSwapBuffers and/or glXSwapBuffers. On MacOS X NSOpenGLViews are automatically swapped.
However most likely you're using some framework, like GLUT, GLFW or Qt, which provide a portable wrapper around those functions. Read the framework's documentation."
I've never used Ray, so I'd say just keep rooting around in the documentation or look through example projects to see how buffer swapping is done.
So I've setup CVPixelBuffer's and tied them to OpenGL FBOs successfully on iOS. But now trying to do the same on OSX has me snagged.
The textures from CVOpenGLTextureCacheCreateTextureFromImage return as GL_TEXTURE_RECTANGLE instead of GL_TEXTURE_2D targets.
I've found the kCVOpenGLBufferTarget key, but it seems like it is supposed to be used with CVOpenGLBufferCreate not CVPixelBufferCreate.
Is it even possible to get GL_TEXTURE_2D targeted textures on OSX with CVPixelBufferCreate, and if so how?
FWIW a listing of the CV PBO setup:
NSDictionary *bufferAttributes = #{ (__bridge NSString *)kCVPixelBufferPixelFormatTypeKey : #(kCVPixelFormatType_32BGRA), (__bridge NSString *)kCVPixelBufferWidthKey : #(size.width), (__bridge NSString *)kCVPixelBufferHeightKey : #(size.height), (__bridge NSString *)kCVPixelBufferIOSurfacePropertiesKey : #{ } };
if (pool)
{
error = CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, pool, &renderTarget);
}
else
{
error = CVPixelBufferCreate(kCFAllocatorDefault, (NSUInteger)size.width, (NSUInteger)size.height, kCVPixelFormatType_32BGRA, (__bridge CFDictionaryRef)bufferAttributes, &renderTarget);
}
ZAssert(!error, #"Couldn't create pixel buffer");
error = CVOpenGLTextureCacheCreate(kCFAllocatorDefault, NULL, [[NSOpenGLContext context] CGLContextObj], [[NSOpenGLContext format] CGLPixelFormatObj], NULL, &textureCache);
ZAssert(!error, #"Could not create texture cache.");
error = CVOpenGLTextureCacheCreateTextureFromImage(kCFAllocatorDefault, textureCache, renderTarget, NULL, &renderTexture);
ZAssert(!error, #"Couldn't create a texture from cache.");
GLuint reference = CVOpenGLTextureGetName(renderTexture);
GLenum target = CVOpenGLTextureGetTarget(renderTexture);
UPDATE: I've been able to successfully use the resulting GL_TEXTURE_RECTANGLE textures. However, this will cause a lot of problems with the shaders for compatibility between iOS and OSX. And anyway I'd rather continue to use normalised texture coordinates.
If it isn't possible to get GL_TEXTURE_2D textures directly from a CVPixelBuffer in this manner, would it be possible to create a CVOpenGLBuffer and have a CVPixelBuffer attached to it to pull the pixel data?
Just came across this, and I'm going to answer it even though it's old, in case others encounter it.
iOS uses OpenGL ES (originally 2.0, then 3.0). OS X uses regular old (non-ES) OpenGL, with a choice of Core profile (3.0+ only) or Compatibility profile (up to 3.2).
The difference here is that OpenGL (non-ES) was designed a long time ago, when there were many restrictions on texture sizes. As cards lifted those restrictions, extensions were added, including GL_TEXTURE_RECTANGLE. Now it's no big deal for any GPU to support any size texture, but for API compatibility reasons they can't really fix OpenGL. Since OpenGL ES is technically a parallel, but separate, API, which was designed much more recently, they were able to correct the problem from the beginning (i.e. they never had to worry about breaking old stuff). So for OpenGL ES they never defined a GL_TEXTURE_RECTANGLE, they just defined that GL_TEXTURE_2D has no size restrictions.
Short answer - OS X uses Desktop OpenGL, which for legacy compatibility reasons still treats rectangle textures separately, while iOS uses OpenGL ES, which places no size restrictions on GL_TEXTURE_2D, and so never offered a GL_TEXTURE_RECTANGLE at all. Thus, on OS X, CoreVideo produces GL_TEXTURE_RECTANGLE objects, because GL_TEXTURE_2D would waste a lot of memory, while on iOS, it produces GL_TEXTURE_2D objects because GL_TEXTURE_RECTANGLE doesn't exist, nor is it necessary.
It's an unfortunate incompatibility between OpenGL and OpenGL ES, but it is what it is and there's nothing to be done but code around it. Or, now, you can (and probably should consider) moving on to Metal.
As this appears to have been left dangling and is something I recently dealt with: no, GL_TEXTURE_RECTANGLE appears to be the only use case. To get to a GL_TEXTURE_2D you're going to have to render to texture.
FWIW, As of 2023, the modern CGLTexImageIOSurface2D is much faster than CVOpenGLESTextureCacheCreateTextureFromImage() for getting CVPixelData into an OpenGL texture. Just ensure your CVPixelbuffers are IOSurface backed by including (id)kCVPixelBufferIOSurfacePropertiesKey: #{}, in the attributes to [[AVPlayerItemVideoOutput alloc] initWithPixelBufferAttributes]
You will still be getting a GL_TEXTURE_RECTANGLE, but you'll be getting it way faster. I made a little shader so that I can render the GL_TEXTURE_RECTANGLE into a GL_TEXTURE_2D bound to a frame buffer.
I've been trying to get OpenGL-ES to do something roughly like the following to see if glPushMatrix() and glPopMatrix() could be used to put things such as blending states back how they were before glPushMatrix() was called.
It works for rotation/translation stuff - why doesn't it work for some other things such as blend states?
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA); //<-first blend mode
glPushMatrix();
glBlendFunc(GL_DST_COLOR, GL_ONE_MINUS_SRC_ALPHA); //<-second blend mode
//...drawing and stuff here...
glPopMatrix();
//at this point it appears the second blend mode is still in effect - why?
Am I properly confused or is there another pop/push combination of functions for states not popped/pushed by glPopMatrix() and glPushMatrix()?
Is there another way to easily set everything back to a previous state? Thanks for any illumination!
A stack for attributes does not exist for OpenGL-ES, sorry.
You can write one yourself if you really want to. All attributes are gettable, so any stack-datastructure would do.
Imho a better way is to define a hand full of useful blending presets and have a little state-machine that allows you to switch from one blending mode to another using the least calls into OpenGL-ES. After all - how many different blendmodes do you really need?
You can use glGet() to get all blending options. Then you can use them to restore the blending state.
As you know, OpenGL is a state machine and the various glPush and glPop functions control stacks. Now, there are multiple stacks. The matrix stack contains only the coordinate transformations. There is another stack, called the attribute stack, which does contain your blend function setting. Check out glPushAttrib.