Michael I GoldMichael I GoldNVIDIA CorporationNVIDIA Corporation

OpenGL InteroperabilityOpenGL Interoperability

What is Interoperability?

•Share memory objects between APIs or contexts within an API

•Share within a device, or between devices

• Implicit or explicit synchronization

Who can play?

•CUDA•OpenCL•OpenGL•Direct3D

CUDA Interoperability

• Import OpenGL buffer objects as CUDA device pointers–Read or write buffer memory directly

from a kernel

– Implicit synchronization within a CPU thread

•Texture support coming soon

CUDA Interop: ExampleApplication

OpenGLdriver

CUDAdriver

Quadro or GeForce

display

Tesla or

GeForceInterop

fast

•Multi-card interop fastest with GL on Quadro. Transfer between cards w/o CPU intervention

•GeForce performs indirect copy, functional but slower

Interop

faster

CUDA example: Initalization// Create a GL buffer object

glBindBuffer(GL_PIXEL_UNPACK_BUFFER, buffer);

glBufferData(GL_PIXEL_UNPACK_BUFFER, buffer_size, NULL, GL_STREAM_COPY);

// Register the buffer object for CUDA interop

cuGLRegisterBufferObject(buffer);

cuGLSetBufferObjectMapFlags(buffer, CU_GL_MAP_RESOURCE_FLAGS_WRITE_DISCARD);

CUDA example: Per-frame usage// map the buffer, invoke a kernel to populate it, and release it back to OpenGL

cuGLMapBufferObjectAsync(&dptr, &size, buffer, stream);

call_kernel(dptr, size);

cuGLUnmapBufferObjectAsync(&dptr, &size, buffer, stream);

// Use the buffer as a pixel buffer object to populate a texture

glTexSubImage2D( … , NULL);

CUDA resources

•Drivers, Toolkit and SDKhttp://www.nvidia.com/cuda

•Forumshttp://forums.nvidia.com

OpenCL Interoperability

•Analogous to CUDA–Create cl_mem from textures and

buffers

•Requires explicit synchronization

OpenCL Shared Objects

OpenCL 3D image object

OpenGL renderbuffer

OpenGL buffer OpenCL buffer object

OpenGL texture 2D(or cubemap face)

OpenGL texture 3D

OpenCL 2D image object

OpenCL 2D image object

clCreateFromGLBuffer

clCreateFromGLTexture2D

clCreateFromGLTexture3D

clCreateFromGLRenderbuffer

OpenGL OpenCL

OpenGL Interoperability• Copy between image objects

– 3D memcpy

– No format conversions

• Copy between dimensionalities– E.g. A slice of a 3D texture and a face of a cubemap

are treated equally

• Copy between GPUs– Complements WGL_NV_gpu_affinity

OpenGL Interop: ExampleApplication

OpenGLdriver

OpenGLdriver

Quadro

display

Quadro

Interop

fast

•Quadro only

•Transfer between cards, no host copy

•Rendering window constrained to affinity GPU

GPU affinity

Offscreen buffer

OpenGL Interop: UsagewglCopyImageSubDataNV(

hSrcRC, srcName, srcTarget, srcLevel, srcX, srcY, srcZ,

hDstRC, dstName, dstTarget, dstLevel, dstX, dstY, dstZ,

width, height, depth);

OpenGL Interop: Resources• NV_copy_image extension specification

http://developer.download.nvidia.com/ opengl/specs/GL_NV_copy_image.txt

• NV_gpu_affinity extension specificationhttp://developer.download.nvidia.com/

opengl/specs/WGL_NV_gpu_affinity.txt

Direct3D Interoperability

• Import Direct3D buffer and image resources into OpenGL

– Vertex and Index buffers -> buffer objects

– Textures and surfaces -> textures and renderbuffers

• Currently WinXP / Direct3D 9 only

• Experimental extension– WGL_NVX_DX_interop

Direct3D Interop: ExampleApplication

OpenGLdriver

DXdriver

Quadroor

GeForce

display

Interop

fast

•OGL can map DX buffers, not the other way

•Single GPU only (at this time)