Hi, I am trying to implement a histogram using the new compute shader support, but I don't seem to be able to read from a texture. I am new to compute shaders, so I might be missing something obvious.
I have attached a modified version of the osgcomputeshaders.cpp file in which I simply load the blueFlowers.png file from the OSG data set, then compute the intensity of each pixel and write it to targetTex. The image comes out black, though. Am I missing something? Thank you! Cheers, Michael ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=53500#53500
/* -*-c++-*- OpenSceneGraph example, osgcomputeshaders. * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ // Written by Wang Rui // This example can work only if GL version is 4.3 or greater #include <osg/Texture2D> #include <osg/Geometry> #include <osg/Geode> #include <osgDB/ReadFile> #include <osgGA/StateSetManipulator> #include <osgViewer/Viewer> #include <osgViewer/ViewerEventHandlers> static char* computeSrc = { "#version 430\n" "uniform image2D targetTex;\n" "uniform sampler2D flowersTexture;\n" "layout (local_size_x = 16, local_size_y = 16) in;\n" "void main() {\n" " ivec2 storePos = ivec2(gl_GlobalInvocationID.xy);\n" " vec4 c = texture2D(flowersTexture, vec2(storePos) / vec2(512,512));\n" " float L = 0.2126 * c.r + 0.7152 * c.g + 0.0722 * c.b;\n" " imageStore(targetTex, storePos, vec4(L, 0.0, 0.0, 0.0));\n" "}\n" }; int main( int argc, char** argv ) { osg::ArgumentParser arguments( &argc, argv ); osg::ref_ptr<osg::Texture2D> flowersTexture = new osg::Texture2D(osgDB::readImageFile("Images/blueFlowers.png")); //flowersTexture->bindToImageUnit(1, osg::Texture::READ_ONLY, GL_RGBA8); // Create the texture as both the output of compute shader and the input of a normal quad osg::ref_ptr<osg::Texture2D> tex2D = new osg::Texture2D; tex2D->setTextureSize( 512, 512 ); tex2D->setFilter( osg::Texture2D::MIN_FILTER, osg::Texture2D::LINEAR ); tex2D->setFilter( osg::Texture2D::MAG_FILTER, osg::Texture2D::LINEAR ); tex2D->setInternalFormat( GL_R32F ); tex2D->setSourceFormat( GL_RED ); tex2D->setSourceType( GL_FLOAT ); tex2D->bindToImageUnit( 0, osg::Texture::WRITE_ONLY ); // So we can use 'image2D' in the compute shader // The compute shader can't work with other kinds of shaders // It also requires the work group numbers. Setting them to 0 will disable the compute shader osg::ref_ptr<osg::Program> computeProg = new osg::Program; computeProg->setComputeGroups( 512/16, 512/16, 1 ); computeProg->addShader( new osg::Shader(osg::Shader::COMPUTE, computeSrc) ); // Create a node for outputting to the texture. // It is OK to have just an empty node here, but seems inbuilt uniforms like osg_FrameTime won't work then. // TODO: maybe we can have a custom drawable which also will implement glMemoryBarrier? osg::Node* sourceNode = osgDB::readNodeFile("axes.osgt"); if ( !sourceNode ) sourceNode = new osg::Node; sourceNode->setDataVariance( osg::Object::DYNAMIC ); sourceNode->getOrCreateStateSet()->setAttributeAndModes( computeProg.get() ); sourceNode->getOrCreateStateSet()->addUniform( new osg::Uniform("targetTex", (int)0) ); sourceNode->getOrCreateStateSet()->addUniform( new osg::Uniform("flowersTexture", (int)1) ); sourceNode->getOrCreateStateSet()->setTextureAttributeAndModes( 0, tex2D.get() ); sourceNode->getOrCreateStateSet()->setTextureAttributeAndModes( 1, flowersTexture.get() ); // Display the texture on a quad. We will also be able to operate on the data if reading back to CPU side osg::Geometry* geom = osg::createTexturedQuadGeometry( osg::Vec3(), osg::Vec3(1.0f,0.0f,0.0f), osg::Vec3(0.0f,0.0f,1.0f) ); osg::ref_ptr<osg::Geode> quad = new osg::Geode; quad->addDrawable( geom ); quad->getOrCreateStateSet()->setMode( GL_LIGHTING, osg::StateAttribute::OFF ); quad->getOrCreateStateSet()->setTextureAttributeAndModes( 0, tex2D.get() ); // Create the scene graph and start the viewer osg::ref_ptr<osg::Group> scene = new osg::Group; scene->addChild( sourceNode ); scene->addChild( quad.get() ); osgViewer::Viewer viewer; viewer.addEventHandler( new osgGA::StateSetManipulator(viewer.getCamera()->getOrCreateStateSet()) ); viewer.addEventHandler( new osgViewer::StatsHandler ); viewer.addEventHandler( new osgViewer::WindowSizeHandler ); viewer.setSceneData( scene.get() ); return viewer.run(); }
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