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| − | = Project Report = | + | = Development Logs = |
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| | == Project Plan == | | == Project Plan == |
| − | BRL-CAD has one of the oldest and fastest parallel ray tracing implementations around but it doesn't currently leverage the GPU very much. With implicit geometry and constructive solid geometry (CSG) Boolean operations, it also has a very different approach to ray tracing that has its own set of academic challenges.
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| − | The project here was to introduce a GPGPU pipeline into BRL-CAD using OpenCL for existing primitives and parallelize them for faster computation compared to the non-GPGPU implementation.
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| − | Some of the primitives that were planned to be converted in this 2020 season of Google Summer of Code are polyhedron with an arbitrary number (ARBN), FASTGEN4 CLINE, hyperboloids of one sheet (HYP), etc.
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| | == Patches Submitted == | | == Patches Submitted == |
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| − | Following patches include modifications for better functioning and resolution of bugs encountered while rendering via OpenCL in MGED terminal.
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| − | * OpenCL_CMAKE: https://sourceforge.net/p/brlcad/patches/549/
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| − | * OpenCL rendering bug: https://sourceforge.net/p/brlcad/patches/551/
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| − | Following are the patches submitted for OpenCL versions of some of the primitives.
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| | * CLINE: https://sourceforge.net/p/brlcad/patches/541/ | | * CLINE: https://sourceforge.net/p/brlcad/patches/541/ |
| | * ARBN: https://sourceforge.net/p/brlcad/patches/543/ | | * ARBN: https://sourceforge.net/p/brlcad/patches/543/ |
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| | * METABALL: https://sourceforge.net/p/brlcad/patches/548/ | | * METABALL: https://sourceforge.net/p/brlcad/patches/548/ |
| | * HYP: https://sourceforge.net/p/brlcad/patches/553/ | | * HYP: https://sourceforge.net/p/brlcad/patches/553/ |
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| | + | * OpenCL_CMAKE: https://sourceforge.net/p/brlcad/patches/549/ |
| | + | * OpenCL rendering bug: https://sourceforge.net/p/brlcad/patches/551/ |
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| | == To Do List == | | == To Do List == |
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| − | * '''Memory Allocation''' : One of the major challenges I faced was finding the OpenCL counterpart of bu_malloc which works fine while passing the variables from .c to .cl file. While I tried with malloc as is used normally in C programs, it apparently didn't work. The renderings were simply not occurring in the OpenCL version. Hence, the HYP and SUPERELL primitives, which didn't use the bu_malloc command, rendered easily while others didn't. The patches submitted above have no compilation or computation error. If the memory allocation thing works, they'd render just as fine.
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| − | * '''Using Printf statement''': Another issue where I got stuck was being unable to use printf statement in OpenCL files. The strategy to debug opencl kernels using printf is to enable printf command by passing enumerations stated below in an array of context properties to the function, clCreateContext, which creates opencl context as follows:
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| − | <pre>
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| − | CL_PRINTF_CALLBACK_ARM 0x40B0
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| − | CL_PRINTF_BUFFERSIZE_ARM 0x40B1
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| − | cl_context_properties context_properties[] =
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| − | {
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| − | CL_PRINTF_CALLBACK_ARM, (cl_context_properties)printf_callback,
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| − | CL_PRINTF_BUFFERSIZE_ARM, (cl_context_properties)0x100000,
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| − | CL_CONTEXT_PLATFORM, (cl_context_properties)platform,
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| − | 0
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| − | };
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| − | </pre>
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| − | This enables the device side printf built in function for OpenCL C versions prior to 1.2. It also extends the cl_context_properties enumeration to allow a user defined printf callback and/or printf buffer size. OpenCL kernel code then has access to:
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| − | #pragma OPENCL EXTENSION cl_arm_printf : enable
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| − | This pragma must be enabled for a kernel to have access to the printf built in function in OpenCL C versions prior to 1.2.
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| − | For the purpose of debugging in mged I used bu_log instead of printf by passing following array of context properties
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| − | <pre>
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| − | cl_context_properties context_properties[] =
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| − | {
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| − | CL_PRINTF_CALLBACK_ARM, (cl_context_properties)bu_log,
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| − | CL_PRINTF_BUFFERSIZE_ARM, (cl_context_properties)0x100000,
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| − | CL_CONTEXT_PLATFORM, (cl_context_properties)platform,
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| − | 0
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| − | };
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| − | </pre>
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| − | But unfortunately this doesn't work and reports error that context cannot be created. This needs further investigation. The print statement would also be useful for debugging the memory allocation issue, as to where and why it is failing.
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| − | == References ==
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| − | * '''Project Plan''': https://brlcad.org/wiki/User:Rishabhsuthar32/GSoC20/Project
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| − | * '''Development Logs''': https://brlcad.org/wiki/User:Rishabhsuthar32/GSoC20/Log
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