The answer has to do with a commonly used feature of OpenGL, called face culling. Face culling is an option for the OpenGL environment which allows the rendering pipeline to ignore not calculate or draw the back face of a shape, saving time, memory and processing cycles:.
If you try to use the face culling feature without knowing which sides of your shapes are the front and back, your OpenGL graphics are going to look a bit thin, or possibly not show up at all. So, always define the coordinates of your OpenGL shapes in a counterclockwise drawing order. Note: It is possible to set an OpenGL environment to treat the clockwise face as the front face, but doing so requires more code and is likely to confuse experienced OpenGL developers when you ask them for help.
Beginning with Android 2. OpenGL ES 2. OpenGL ES 3. The 1. You should carefully consider the graphics requirements and choose the API version that works best for your application.
For more information on checking for availability of the 3. Texture compression can significantly increase the performance of your OpenGL application by reducing memory requirements and making more efficient use of memory bandwidth. Caution: The ETC1 format is supported by most Android devices, but is not guaranteed to be available.
Note: The ETC1 texture compression format does not support textures with a transparency alpha channel. If your application requires textures with transparency, you should investigate other texture compression formats available on your target devices. This texture format offers excellent compression ratios with high visual quality and the format also supports transparency alpha channel. You should investigate texture compression support on the devices you are are targeting to determine what compression types your application should support.
In order to determine what texture formats are supported on a given device, you must query the device and review the OpenGL extension names , which identify what texture compression formats and other OpenGL features are supported by the device. Some commonly supported texture compression formats are as follows:.
Warning: These texture compression formats are not supported on all devices. Support for these formats can vary by manufacturer and device. For information on how to determine what texture compression formats are on a particular device, see the next section.
Using this declaration enables filtering by external services such as Google Play, so that your app is installed only on devices that support the formats your app requires. For details, see OpenGL manifest declarations. These extensions include texture compressions, but typically also include other extensions to the OpenGL feature set. To determine what texture compression formats, and other OpenGL extensions, are supported on a particular device:. Warning: The results of this call vary by device model!
You must run this call on several target devices to determine what compression types are commonly supported. Packaging these extensions together encourages a consistent set of functionality across devices, while allowing developers to take full advantage of the latest crop of mobile GPU devices.
The AEP also improves support for images, shader storage buffers, and atomic counters in fragment shaders. In addition, the platform version must support it. The following code snippet shows an example of how to do so:. If the method returns true, AEP is supported. You can specify the minimum version of the API your application requires in your manifest , but you may also want to take advantage of features in a newer API at the same time.
Before using OpenGL ES features from a version higher than the minimum required in your application manifest, your application should check the version of the API available on the device. You can do this in one of two ways:. The following code example demonstrates how to check the OpenGL ES version by creating a minimum supported context first, and then checking the version string:. OpenGL ES 1. While performance, compatibility, convenience, control and other factors may influence your decision, you should pick an OpenGL API version based on what you think provides the best experience for your users.
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You might need to learn some more math concepts, but after you get to the intermediate level. But that totally depends upon you. You can pass over many things with the help of different libraries.
Therefore, OpenGL is a completely functional API that is primitive-level and allowing the programmer to effectively address and take advantage of graphics hardware.
A large number of high-level libraries as well as applications use OpenGL because of its performance, programming ease, extensibility as well as widespread support. This has been a guide to OpenGL in Android. You can also go through our other suggested articles to learn more —. Submit Next Question. By signing up, you agree to our Terms of Use and Privacy Policy.
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