SLNodeLOD.cpp

Go to the documentation of this file.

/**
 * \file      SLNodeLOD.cpp
 * \date      July 2021
 * \authors   Jan Dellsperger, Marcus Hudritsch
 * \copyright http://opensource.org/licenses/GPL-3.0
 * \remarks   Please use clangformat to format the code. See more code style on
 *            https://github.com/cpvrlab/SLProject4/wiki/SLProject-Coding-Style
*/
 
#include <SLSceneView.h>
#include <SLNodeLOD.h>
 
//-----------------------------------------------------------------------------
//! Adds an LOD node with forced decreasing min LOD coverage
/*!
 * The coverage value is the ratio of the nodes bounding rectangle in screen space
 * to the full viewport. The minLodCoverage value must be > 0.0 and < 1.0 and
 * < than the minLodCoverage of the last node in the LOD group. If the first
 * child node has e.g. a minLodCoverage of 0.1 it means that it will be visible
 * if its bounding rectangle covers more then 10% of the viewport. The first
 * child node in the group must be the one with the highest resolution.\n
 * @remarks It is important that during instantiation NO OpenGL functions (gl*) 
 * get called because this constructor will be most probably called in a parallel 
 * thread from within an SLScene::registerAssetsToLoad or SLScene::assemble 
 * function. All objects that get rendered have to do their OpenGL initialization 
 * when they are used the first time during rendering in the main thread.
 * \param childToAdd LOD child node pointer to add
 * \param minLodCoverage A value > 0 and < 1 and < than the minLodCoverage
 * of the last node in the LOD group
 * \param levelForSM Level to use for shadow mapping (0 uses the active level)
 */
void SLNodeLOD::addChildLOD(SLNode* childToAdd,
                            SLfloat minLodCoverage,
                            SLubyte levelForSM)
{
    assert(minLodCoverage > 0.0f &&
           minLodCoverage < 1.0f &&
           "SLNodeLOD::addChildLOD min. LOD limit must be > 0 and < 1");
 
    if (!_children.empty() &&
        _children[_children.size() - 1]->minLodCoverage() <= minLodCoverage)
        SL_EXIT_MSG("SLNodeLOD::addChildLOD: A new child LOD node must have a smaller LOD limit than the last one.");
 
    childToAdd->minLodCoverage(minLodCoverage);
    childToAdd->levelForSM(levelForSM);
    addChild(childToAdd);
 
    /* Set new node hidden, so they won't be shadowed if they are outside
     * the view frustum. Only the LOD algorithm in cullChildren3D can make
     * them visible */
    childToAdd->drawBits()->set(SL_DB_HIDDEN, true);
}
//-----------------------------------------------------------------------------
//! Culls the LOD children by evaluating the the screen space coverage
void SLNodeLOD::cullChildren3D(SLSceneView* sv)
{
    if (!_children.empty())
    {
        SLfloat rectCoverage = _aabb.rectCoverageInSS();
 
        // Set visibility (draw-bit SL_DB_HIDDEN) for each level
        for (SLint i = 0; i < _children.size(); ++i)
        {
            bool isVisible;
 
            if (i == 0)
                isVisible = rectCoverage >= _children[i]->minLodCoverage();
            else
                isVisible = rectCoverage < _children[i - 1]->minLodCoverage() &&
                            rectCoverage >= _children[i]->minLodCoverage();
 
            _children[i]->drawBits()->set(SL_DB_HIDDEN, !isVisible);
            _aabb.isVisible(isVisible);
 
            // cull check only the visible level
            if (isVisible)
                _children[i]->cull3DRec(sv);
        }
    }
}
//-----------------------------------------------------------------------------