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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