OpenCL / OpenGL Texture Interoperability: An Image Blurring Case Study

Transcription

1 1 OpenCL / OpenGL Texture Interoperability: An Image Blurring Case Study Mike Bailey mjb@cs.oregonstate.edu opencl.opengl.rendertexture.pptx

2 OpenCL / OpenGL Texture Interoperability: The Basic Idea 2 Application Program: 1. Renders to an OpenGL Texture 2. Executes an OpenCL kernel 3. Renders from an OpenGL Texture OpenGL uses GPU to render to a texture OpenCL uses GPU, treating the input and output textures as image2d_t data types OpenGL uses GPU to render from a texture onto a quad Input Texture Output Texture

3 More OpenGL Rendering Context 3 The OpenGL Rendering Context contains all the characteristic information necessary to produce an image from geometry. This includes transformations, colors, lighting, textures, where to send the display, etc. Array Buffer Color Element Array Buffer Lighting Texture0 Texture1 Context Transformation Display Dest. Some of these characteristics have a default value (e.g., lines are white, the display goes to the screen) and some have nothing (e.g., no textures exist)

4 OpenCL Global Variables 4 GLuint GLuint GLuint double int FrameBuffer; DepthBuffer; RenderToTexture, RenderFromTexture; ElapsedTime; ShowPerformance; size_t GlobalWorkSize[3] = { SIZES, SIZET, 1 }; size_t LocalWorkSize[3] = { LOCAL_SIZE, LOCAL_SIZE, 1 }; cl_context cl_command_queue cl_device_id cl_kernel cl_platform_id cl_program cl_platform_id cl_mem cl_mem Context; CmdQueue; Device; Kernel; Platform; Program; PlatformID; ReadFromImage; WriteToImage; Note that the host application calls these cl_mem, but the kernel will call them image2d_t

5 5 How to Create Empty OpenGL Textures and a Non-screen Framebuffer glgenframebuffers( 1, &FrameBuffer ); glgenrenderbuffers( 1, &DepthBuffer ); glgentextures( 1, &RenderToTexture ); glgentextures( 1, &RenderFromTexture ); glbindframebuffer( GL_FRAMEBUFFER, FrameBuffer ); glbindrenderbuffer( GL_RENDERBUFFER, DepthBuffer ); glrenderbufferstorage( GL_RENDERBUFFER, GL_DEPTH_COMPONENT, SIZES, SIZET ); glframebufferrenderbuffer( GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, DepthBuffer ); glbindtexture( GL_TEXTURE_2D, RenderFromTexture ); glteximage2d( GL_TEXTURE_2D, 0, 4, SIZES, SIZET, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL ); gltexparameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP ); gltexparameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP ); gltexparameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ); gltexparameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glbindtexture( GL_TEXTURE_2D, RenderToTexture ); glteximage2d( GL_TEXTURE_2D, 0, 4, SIZES, SIZET, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL ); gltexparameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP ); gltexparameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP ); gltexparameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ); gltexparameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glframebuffertexture2d( GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, RenderToTexture, 0 ); GLenum status = glcheckframebufferstatus( GL_FRAMEBUFFER ); if( status!= GL_FRAMEBUFFER_COMPLETE ) fprintf( stderr, "FrameBuffer is not complete.\n" ); glbindframebuffer( GL_FRAMEBUFFER, 0 );

6 Turning those Textures into OpenCL Memory Objects 6 ReadFromImage = clcreatefromgltexture2d( Context, CL_MEM_READ_ONLY, GL_TEXTURE_2D, 0, RenderToTexture, &status ); WriteToImage = clcreatefromgltexture2d( Context, CL_MEM_WRITE_ONLY, GL_TEXTURE_2D, 0, RenderFromTexture, &status ); Note that the host application calls these cl_mem, but the kernel will call them image2d_t

7 Either OpenGL or OpenCL Can Use the Textures at a Time, but not Both 7 OpenGL renders to the first texture OpenCL acquires the textures Image Data in two OpenGL Texture Objects Each OpenCL kernel reads a pixel and its surrounding pixels from the first texture Each OpenCL kernel performs the blurring operation Each OpenCL kernel writes its pixel value back to the second texture OpenCL Releases the Textures OpenGL renders using the second texture

8 A Deceptively-Simple Main Program 8 int main( int argc, char *argv[ ] ) { glutinit( &argc, argv ); InitGraphics( ); InitLists( ); InitCL( ); Reset( ); InitGlui( ); glutmainloop( ); return 0; }

9 Setup the Kernel Arguments 9 void InitCL( ) {... // 10. setup the arguments to the Kernel object: status = clsetkernelarg( Kernel, 0, sizeof(cl_mem), &ReadFromImage ); status = clsetkernelarg( Kernel, 1, sizeof(cl_mem), &WriteToImage ); status = clsetkernelarg( Kernel, 2, sizeof(int), &ApplyFilter ); to Match the Kernel s Parameter List kernel void Filter( global read_only image2d_t readfromimage, global write_only image2d_t writetoimage, int applyfilter ) {... }

10 OpenCL Does Its Computing in the Middle of the Display Callback 10 glbindframebuffer( GL_FRAMEBUFFER, FrameBuffer ); glfinish( ); << draw the scene >> // do the opencl computing: cl_int status = clenqueueacquireglobjects( CmdQueue, 1, &ReadFromImage, 0, NULL, NULL ); status = clenqueueacquireglobjects( CmdQueue, 1, &WriteToImage, 0, NULL, NULL ); // 11. enqueue the Kernel object for execution: status = clsetkernelarg( Kernel, 2, sizeof(int), &ApplyFilter ); // because this is from a dynamic checkbox cl_event wait; status = clenqueuendrangekernel( CmdQueue, Kernel, 2, NULL, GlobalWorkSize, LocalWorkSize, 0, NULL, &wait ); clfinish( CmdQueue ); // do the opengl drawing with the computed texture: status = clenqueuereleaseglobjects( CmdQueue, 1, &ReadFromImage, 0, NULL, NULL ); status = clenqueuereleaseglobjects( CmdQueue, 1, &WriteToImage, 0, NULL, NULL ); // render to the real framebuffer :

11 OpenCL Does Its Computing in the Middle of the Display Callback // render to the real framebuffer : 11 glbindframebuffer( GL_FRAMEBUFFER, 0 ); glclear( GL_COLOR_BUFFER_BIT GL_DEPTH_BUFFER_BIT ); glenable( GL_DEPTH_TEST ); glshademodel( GL_FLAT ); vx = glutget( GLUT_WINDOW_WIDTH ); vy = glutget( GLUT_WINDOW_HEIGHT ); V = vx < vy? vx : vy; // minimum dimension Xl = ( vx - v ) / 2; yb = ( vy - v ) / 2; glviewport( xl, yb, v, v ); gldisable( GL_DEPTH_TEST ); glmatrixmode( GL_PROJECTION ); glloadidentity( ); gluortho2d( 0., 100., 0., 100. ); glmatrixmode( GL_MODELVIEW ); glloadidentity( ); glenable( GL_TEXTURE_2D ); glbindtexture( GL_TEXTURE_2D, RenderFromTexture ); gltexenvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE ); glbegin( GL_QUADS ); gltexcoord2f( 0., 0. ); glvertex2f( 0., 0. ); gltexcoord2f( 1., 0. ); glvertex2f( 100., 0. ); gltexcoord2f( 1., 1. ); glvertex2f( 100., 100. ); gltexcoord2f( 0., 1. ); glvertex2f( 0., 100. ); glend( ); gldisable( GL_TEXTURE_2D );

12 13. Clean-up 12 void Quit( ) { Glui->close( ); glutsetwindow( MainWindow ); glfinish( ); glutdestroywindow( MainWindow ); // 13. clean everything up: clreleasekernel( Kernel ); clreleaseprogram( Program ); clreleasecommandqueue( CmdQueue ); clreleasememobject( ReadFromImage ); clreleasememobject( WriteToImage ); } exit( 0 );

13 typedef float4 color; rendertexture.cl 13 kernel void Filter( global read_only image2d_t readfromimage, global write_only image2d_t writetoimage, int applyfilter ) { const sampler_t SAMPLER = CLK_NORMALIZED_COORDS_FALSE CLK_ADDRESS_CLAMP_TO_EDGE CLK_FILTER_LINEAR; int is = get_global_id( 0 ); int it = get_global_id( 1 ); int2 ist00 = (int2)( is, it ); color c00 = read_imagef( readfromimage, SAMPLER, ist00 ); if( applyfilter == 0 ) { write_imagef( writetoimage, ist00, c00 ); return; } int2 istp0 = ist00 + (int2)( 1, 0 ); int2 istm0 = ist00 - (int2)( 1, 0 ); int2 ist0p = ist00 + (int2)( 0, 1 ); int2 ist0m = ist00 - (int2)( 0, 1 ); int2 istpp = ist00 + (int2)( 1, 1 ); int2 istmm = ist00 - (int2)( 1, 1 ); int2 istpm = ist00 + (int2)( 1, -1 ); int2 istmp = ist00 - (int2)( 1, -1 ); } color cp0 = read_imagef( readfromimage, SAMPLER, istp0 ); color cm0 = read_imagef( readfromimage, SAMPLER, istm0 ); color c0p = read_imagef( readfromimage, SAMPLER, ist0p ); color c0m = read_imagef( readfromimage, SAMPLER, ist0m ); color cpp = read_imagef( readfromimage, SAMPLER, istpp ); color cmm = read_imagef( readfromimage, SAMPLER, istmm ); color cpm = read_imagef( readfromimage, SAMPLER, istpm ); color cmp = read_imagef( readfromimage, SAMPLER, istmp ); color result = ( 4.*c *(cp0 + cm0 + c0p + c0m) + (cpp + cmm + cpm + cmp) ) / 16.; result.w = 1.; // alpha write_imagef( writetoimage, (int2)( is, it ), result ); 3x3 Blur Filter:

14 14 Original 3x3 Blur Filter

15 Jane Parallel s Performance 15 MegaPixels / Second Local Work Group Size