There're set of definition called "egl" in GLES 1.1: http://www.khronos.org/opengles/sdk/1.1/docs/man/
It's the "Native Platform Graphics Interface Layer":
http://www.khronos.org/opengles/
However, they're not in GLES 2.0: http://www.khronos.org/opengles/sdk/docs/man/
So I got some questions:
Is this a separated spec from GLES? Or a part of GLES1.1?
Where did they gone (in 2.0)? Or still exist (in 2.0)?
Where is the manual (guide)?
Should I manage eglContext in GLES 2.0 too?
EGL is a separate spec from OpenGL ES, it can manage contexts for OpenGL ES 1.0/1.1 and OpenGL ES 2.0 (and algo OpenVG), so it's not really gone.
The latest spec is here.
I think eonil was premature to accept the answer. Unless I am consistently missing things at the "latest spec" Valdenegro provided. For what I find there is that in order to choose the client API for the current context, one must use EGL_CONTEXT_CLIENT_VERSION, which is itself supported only in EGL 1.2, which is not on any Android phone I have seen: they are all EGL 1.1.
In EGL 1.0 or 1.1, you can only use the default client version, which is openGL ES.
Related
Previously I'm using OpenGL on Mac via glew 2.1.0 and JUCE5, but it can only access OpenGL 2.1 APIs. I can't believe that my Macbook Air (Intel Graphics) bought on 2018 can only provide this, and I'm tired to maintain two sets of API calls and shaders for 2.1 and 3.X separately. Then I tried to replace all #include <GL/glew.h> with #include <OpenGL/gl3.h>, then link with OpenGL framework directly. However, the program still failed to compile a #version 130 shader (it claims not supported).
Here I want to know that:
Does all recent Apple devices (after 2010) capable for OpenGL 3.0?
How to turn on OpenGL 3.0 support on MacOS?
Finally I found the way: I have to enable it on JUCE side. When JUCE's OpenGL context is created, I must explicitly set expected OpenGL version by setOpenGLVersionRequired( juce::OpenGLContext::openGL3_2 ) before using it.
IMPORTANT: this would still lead failure to a compile to #version 130 shader, as Apple would strictly deprecate all old features prior to specified API version. A simple workaround is to dynamically prepend a version declaration according to system type, as GLSL 1.3.0 features is mostly included by GLSL 1.5.0.
I am trying to make use of some ES 3.1 features, and it's unclear if this is supported:
I notice that there is an OpenGL ES 3.1 header in the emscripten repository which defines some of the functions I'm looking for, and I can include them successfully in my project. However, they are not available when I try to link:
error: undefined symbol: glDispatchCompute (referenced by top-level compiled C/C++ code)
warning: _glDispatchCompute may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
The documentation says that OpenGL ES3 is supported if I specify -s FULL_ES3=1 (which I am doing).
Since there are headers for it, is this functionality available? If so, how do I enable support for it? (Does it require manually loading extensions or enabling experimental support in emscripten, for example?)
First thing to realize, is that decent Browsers currently implement only WebGL 1.0 (based on OpenGL ES 2.0) and WebGL 2.0 (based on OpenGL ES 3.0). So that Emscripten SDK may implement only features presented by WebGL 2.0 + extensions, and, unfortunately, Compute Shaders are not presented in any way in WebGL (and there are no more plans to add this functionality in future).
By the way, WebGL 2.0 support has been added to Safari 15 (iOS 15) only this (2021) year, so that even OpenGL ES 2.0 will not work on all devices.
I notice that there is an OpenGL ES 3.1 header in the emscripten
The extra <GLES3\gl3*.h> headers are there not because Emscripten implements all of them, but because this is a common way to distribute OpenGL ES 3.x headers that existing applications may rely on to conditionally load / use OpenGL ES 3.x functions at runtime, when they available.
The documentation says that OpenGL ES3 is supported if I specify -s FULL_ES3=1 (which I am doing).
I think that documentation is more or less clear about what FULL_ES3=1 adds:
To enable OpenGL ES 3.0 emulation, specify the emcc option -s FULL_ES3=1 when linking the final executable (.js/.html) of the project.
This adds emulation for mapping memory blocks to client side memory.
There is no word about OpenGL ES 3.1 here, nor a reason to expect a wonder from Emscripten, as I can barely imagine a reasonable hardware-accelerated way to emulate things like Compute Shaders on top of OpenGL ES 3.0. And software emulation would be certainly of no use for most applications.
WebGPU 1.0 that promised to appear mid '2022, is more capable than WebGL 2.0. So that WebGPU developers already see that at one time native WebGL 2.0 implementation in the Browsers could be replaced by a WebAssembly module implementing this legacy API on top of WebGPU - but in some very distant future. The same could also bring OpenGL ES 3.1/3.2 features to Emscripten SDK - at least theoretically, if somebody will be still interested to work on this.
I know that OpenGL ES 2.0 standard threw out all the methods that can achieve the same results only keeping one. This is the result why static pipeline is removed from the specification and only dynamic pipeline is present. But it is strange that I use this code and it works:
glColor3f(0, 1, 1);//white
glBegin(GL_LINE_LOOP);
glVertex2f(lower.x, lower.y);
glVertex2f(upper.x, lower.y);
glVertex2f(upper.x, upper.y);
glVertex2f(lower.x, upper.y);
glEnd();
This API function I use belong to static pipeline, right as I draw without using a shader. BTW I do this is cocos2d-x 3.5 that is based on OpenGL ES 2.0.
BTW I do this is cocos2d-x 3.5 that is based on OpenGL ES 2.0.
From the cocos2d-x github page (my emphasis):
OpenGL ES 2.0 (mobile) / OpenGL 2.1 (desktop) based
You are very likely not using an GLES2 context at all, but a GL 2.1 one, which does support all of those legacy features like the fixed function pipeline and immediate mode.
Note that the immediate mode (glBegin/glEnd) was never a feature of GLES, not even in 1.x which did implement the fixed-function pipeline. It does only exist in legacy desktop GL. Your code will fail if you run it on mobile devices.
I'm trying to build OpenSceneGraph 3.2 for the Ubuntu armhf architecture, but I'm getting a compile error about a symbol not found. The symbol in question is glReadBuffer. I looked at GLES2/gl2.h header, and indeed, that symbol is not there. However, the symbol is present in GLES3/gl3.h, and documentation online suggests that the function was added in OpenGL ES 3.0. However, I did find a function named glReadBufferNV in GLES2/gl2ext.h (which is not #include'd in the source files.
I'm wondering if glReadBufferNV can be used instead of glReadBuffer, and what might be the possible side effects. I'm suspecting that the NV stands for Nvidia, and that it is a Nvidia-only implementation. Is this correct? If so, is there any way to get glReadBuffer in OpenGL ES 2.0 (I am under the impression that OpenSceneGraph can be built under OpenGL ES 2.0)?
Edit: As it turned out, the code that builds this portion of OpenSceneGraph was excluded when building with OpenGL ES or OpenGL 3.0. However, I'm still interested in what's special about glReadBufferNV.
As your research suggests, glReadBuffer was added to ES for 3.0; it is not defined in 2.0. Prior to that, as per the header file you found, an extension defined glReadBufferNV — specifically the NV_read_buffer extension.
So what's happened is that something wasn't in the spec, at least Nvidia thought it would be useful, so they've implemented an OpenGL extension, which has subsequently been discussed at Khronos, had all the edge cases or ambiguities dealt with and has eventually made its way into the core spec.
That's generally how GL development proceeds: extensions come along to provide functionality that's not yet in the main library, they're discussed and refined and adopted into the core spec if appropriate.
Comparing the official specification for glReadBuffer with the extension documentation, the extension has a few ties into other extensions that you wouldn't expect to make it into the core spec (e.g. COLOR_ATTACHMENTi_NV is supported as a source) but see resolved issue 7:
Version 6 of this specification isn't compatible with OpenGL ES 3.0.
For contexts without a back buffer, this extension makes FRONT the
default read buffer. ES 3.0 instead calls it BACK.
How can this be harmonized?
RESOLVED: Update the specification to match ES 3.0 behavior. This
introduces a backwards incompatibility, but few applications are
expected to be affected. In the EGL ecosystem where ES 2.0 is
prevalent, only pixmaps have no backbuffer and their usage remains
limited.
So the extension has retroactively been modified to bring it into line with what was agreed for the core spec.
I see that glFenceSync does not exist in OpenGL ES 2.0, it was added only in OpenGL ES 3.0.
Does OpenGL ES 2.0 offer any alternative of syncing between CPU and GPU, aside from the brutal force glFinish?
You have different calls in OpenGL ES 2.0 that give some insight into different matters concerning GL, but mainly, you're left with glFinish only.
In glext.h.
GL_API GLsync glFenceSyncAPPLE(GLenum condition, GLbitfield flags) __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_6_0);
I am pretty sure this is what you want. Anyway available only on iOS 6.0 or later.