vec4 GpuParrallelReductionApp::findMindMax()
{
// init the programs, fbo and texture used for the parrallel reduction
static gl::FboRef sReductionFbo, sReadFbo;
static gl::Texture2dRef sReductionTexture0;
static gl::GlslProgRef sReductionProg, sCopyProg;
auto startingSize = mFbo->getSize() / 2;
if( !sReductionFbo || sReductionFbo->getSize() != startingSize ) {
sReductionTexture0 = gl::Texture2d::create( startingSize.x, startingSize.y, gl::Texture2d::Format().minFilter( GL_NEAREST_MIPMAP_NEAREST ).magFilter( GL_NEAREST ).mipmap().immutableStorage() );
sReductionFbo = gl::Fbo::create( startingSize.x, startingSize.y, gl::Fbo::Format()
.attachment( GL_COLOR_ATTACHMENT0, sReductionTexture0 )
.disableDepth() );
sReductionProg = gl::GlslProg::create( loadAsset( "minMax.vert" ), loadAsset( "minMax.frag" ) );
}
// start reduction profiling
static auto sTimer0 = gl::QueryTimeSwapped::create();
sTimer0->begin();
// attach the main level of the texture
gl::ScopedFramebuffer scopedFbo( sReductionFbo );
glFramebufferTexture2D( GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, sReductionTexture0->getId(), 0 );
// start by blitting the main fbo into the reduction one
mFbo->blitTo( sReductionFbo, mFbo->getBounds(), sReductionFbo->getBounds(), GL_NEAREST );
// bind the reduction program and texture and disable blending
gl::ScopedMatrices scopedMatrices;
gl::ScopedGlslProg scopedGlsl( sReductionProg );
gl::ScopedBlend scopedBlend( false );
gl::ScopedTextureBind scopedTexBind0( sReductionTexture0, 0 );
sReductionProg->uniform( "uTex0", 0 );
// iterate trough each mipmap level
int numMipMaps = gl::Texture2d::requiredMipLevels( startingSize.x, startingSize.y, 0 );
for( int level = 1; level < numMipMaps; ++level ) {
// attach the current mipmap level to the framebuffer and limit texture sampling to the previous level
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, level - 1 );
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, level - 1 );
glFramebufferTexture2D( GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, sReductionTexture0->getId(), level );
// get the current mipmap size and update uniforms
vec2 size = gl::Texture2d::calcMipLevelSize( level, sReductionFbo->getWidth(), sReductionFbo->getHeight() );
sReductionProg->uniform( "uInvSize", vec2( 1.0f ) / vec2( size ) );
// render a fullscreen quad
gl::ScopedViewport scopedViewport( ivec2( 0 ), size );
gl::setMatricesWindow( size.x, size.y );
gl::drawSolidRect( Rectf( vec2( 0.0f ), vec2( size ) ) );
}
// stop reduction profiling
sTimer0->end();
mReductionTime = sTimer0->getElapsedMilliseconds();
// start readback profiling
static auto sTimer1 = gl::QueryTimeSwapped::create();
sTimer1->begin();
// read back to the cpu and find the max value
vec4 max( 0.0f );
ivec2 readSize = gl::Texture2d::calcMipLevelSize( numMipMaps - 1, startingSize.x, startingSize.y );
Surface8u surface( readSize.x, readSize.y, true );
glGetTexImage( sReductionTexture0->getTarget(), numMipMaps - 1, GL_RGBA, GL_UNSIGNED_BYTE, surface.getData() );
auto it = surface.getIter();
while( it.line() ) { while( it.pixel() ) {
max = glm::max( max, vec4( it.r(), it.g(), it.b(), it.a() ) );
} }
// stop readback profiling
sTimer1->end();
mReadBackTime = sTimer1->getElapsedMilliseconds();
return max;
}
void PTWeekend::cleanup()
{
GLuint textureName = imgTex->getId();
glDeleteTextures(1, &textureName);
}
