Direct access to OpenGL texture memory
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CONFIDENTIAL ©2013 GlobalLogic Inc. by Rostyslav Lesovyi OpenGL's texture DMA DMA stands for Direct Memory Access
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This presentation regards working with graphic applications, and in particular it deals with OpenGL's texture direct memory access. Presentation by Rostyslav Lesovyi, Software engineer, GlobalLogic. Mobile TechTalk, Lviv, 2014. More details - www.globallogic.com.ua/press-releases/mobile-techtalk-lviv/
Transcript of Direct access to OpenGL texture memory
CONFIDENTIAL©2013 GlobalLogic Inc.
by Rostyslav Lesovyi
OpenGL's texture DMADMA stands for Direct Memory Access
©2013 GlobalLogic Inc. CONFIDENTIAL
CONFIDENTIAL
• Async texture upload
• Rapid updates of texture or its parts
• Texture data download
Problems
CONFIDENTIAL
• Simple download/upload
• Shared OpenGL contexts
• PBO (Pixel Buffer Objects)
• EGLImage and GraphicBuffer
Solutions
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Pros:
• very easy to use and understand
Cons:
• super slow!!!
• operates in a single thread
• glTexImage2D/glTexSubImage2D for upload• glReadPixels for download
Simple download/upload
CONFIDENTIAL
• create background thread
• create shared OpenGL context
• attach context to background thread
• use glTexImage2D, glTexSubImage2D or glReadPixels
What to do
Shared OpenGL contexts
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EGLContext context =egl.eglCreateContext(display, config, parentContext, null);
EGLSurface surface =egl.eglCreatePbufferSurface(display, config, surfaceAttributes);
Shared context creation:
Shared OpenGL contexts
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EGLContext context =egl.eglCreateContext(display, config, parentContext, null);
EGLSurface surface =egl.eglCreatePbufferSurface(display, config, surfaceAttributes);
Shared OpenGL contexts
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Pros:
• relatively easy to use
• full threading support
Cons:
• relying on slow functions
Shared OpenGL contexts
More info:https://github.com/pcwalton/test-async-texture-upload
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Pixel Buffer Objects
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Pixel Buffer ObjectsPros:
• relatively easy to use
• supports asynchronous upload/download
Cons:
• Android 4.3+ / OpenGL ES 3.0
• hard to use for two-ways texture updates
• still copies from PBO to CPU and vice versa
More info:http://www.songho.ca/opengl/gl_pbo.html
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EGLImage and GraphicBuffer
= Texture image data (actual pixels)
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EGLImage and GraphicBufferPros:
• direct access to texture’s pixel data
• can be accessed by any thread
• supported by Android 2.0.1+
Cons:
• requires NDK
• requires usage of ARM library
More info:https://wiki.mozilla.org/Platform/GFX/Gralloc
CONFIDENTIAL©2013 GlobalLogic Inc.
Q&A
CONFIDENTIAL©2013 GlobalLogic Inc.
Thank you
