OpenSpace/modules/globebrowsing/rendering/chunkrenderer.h

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* OpenSpace                                                                             *
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* Copyright (c) 2014-2016                                                               *
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#ifndef __CHUNK_RENDERER_H__
#define __CHUNK_RENDERER_H__

#include <memory>
#include <glm/glm.hpp>

// open space includes
#include <openspace/rendering/renderable.h>
#include <modules/globebrowsing/geometry/geodetic2.h>
#include <modules/globebrowsing/geometry/ellipsoid.h>
#include <modules/globebrowsing/meshes/grid.h>
#include <modules/globebrowsing/rendering/layershadermanager.h>
#include <modules/globebrowsing/tile/tileselector.h>
#include <modules/globebrowsing/chunk/chunknode.h>

#include <ghoul/opengl/textureunit.h>

namespace ghoul {
namespace opengl {
    class ProgramObject;
}
}

namespace openspace {
namespace globebrowsing {

    class ChunkRenderer {
    public:
        ChunkRenderer(std::shared_ptr<Grid> grid,
            std::shared_ptr<LayerManager> layerManager);

        /**
         Chooses to render a chunk either locally or globally depending on the chunklevel
         of the <code>Chunk</code>.
        */
        void renderChunk(const Chunk& chunk, const RenderData& data);
        void update();

    private:
        /**
         Chunks can be rendered either globally or locally. Global rendering is performed
         in the model space of the globe. With global rendering, the vertex positions
         of a chunk are calculated in the vertex shader by transforming the geodetic
         coordinates of the chunk to model space coordinates. We can only achieve floating
         point precision by doing this which means that the camera too close to a global
         tile will lead to jagging. We only render global chunks for lower chunk levels.
        */
        void renderChunkGlobally(const Chunk& chunk, const RenderData& data);

        /**
         Local rendering of chunks are done using linear interpolation in camera space.
         All four corner points of the chunk are calculated in double precision on the
         CPU and transformed to camera space with double precision matrix transforms.
         These positions can then be cast to floats and uploaded to the vertex shader.
         The vertex shader rendering performs linear interpolation between the four
         corner points to get the resulting chunk. This means that there will be an error
         due to the curvature of the globe. The smaller the patch is (with higher chunk
         levels) the better the approximation becomes. This is why we only render local
         chunks for higher chunk levels.
        */
        void renderChunkLocally(const Chunk& chunk, const RenderData& data);


        ProgramObject* getActivatedProgramWithTileData(
            std::shared_ptr<LayerShaderManager> layeredShaderManager,
            std::shared_ptr<GPULayerManager> gpuLayerManager,
            const Chunk& chunk);

        // shared pointer to a grid which can be the same for all rendered chunks.
        std::shared_ptr<Grid> _grid;
        std::shared_ptr<LayerManager> _layerManager;

        // Two different shader programs. One for global and one for local rendering.
        std::shared_ptr<LayerShaderManager> _globalLayerShaderManager;
        std::shared_ptr<LayerShaderManager> _localLayerShaderManager;

        // Layered texture uniforms are chached in the uniform ID handles.
        std::shared_ptr<GPULayerManager> _globalGpuLayerManager;
        std::shared_ptr<GPULayerManager> _localGpuLayerManager;
    };

} // namespace globebrowsing
} // namespace openspace

#endif  // __CHUNK_RENDERER_H__