OpenSpace/modules/base/rendering/renderabletrail.h

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 * OpenSpace                                                                             *
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#ifndef __OPENSPACE_MODULE_BASE___RENDERABLETRAIL___H__
#define __OPENSPACE_MODULE_BASE___RENDERABLETRAIL___H__

#include <openspace/rendering/renderable.h>

#include <openspace/properties/misc/optionproperty.h>
#include <openspace/properties/misc/stringproperty.h>
#include <openspace/properties/scalar/boolproperty.h>
#include <openspace/properties/scalar/floatproperty.h>
#include <openspace/properties/scalar/intproperty.h>
#include <openspace/properties/vector/vec2property.h>
#include <openspace/properties/vector/vec3property.h>
#include <openspace/properties/vector/vec4property.h>
#include <ghoul/misc/managedmemoryuniqueptr.h>
#include <ghoul/opengl/ghoul_gl.h>
#include <ghoul/opengl/uniformcache.h>

namespace ghoul::opengl {
    class ProgramObject;
    class Texture;
} // namespace ghoul::opengl

namespace openspace {

namespace documentation { struct Documentation; }

class Translation;

/**
 * This is the base class for a trail that is drawn behind an arbitrary object. The two
 * concreate implementations are RenderableTrailOrbit, for objects that have a (roughly)
 * repeating orbit, and RenderableTrailTrajectory, for objects that are less orbit-like.
 * The main difference between two subclasses is that RenderableTrailOrbit updates itself
 * continously, whereas RenderableTrailTrajectory precomputes the entire trail in advance.
 *
 * This class is responsible for the rendering of the vertex buffer objects which are
 * filled by the subclasses. The buffers contain a list of TrailVBOLayout objects that is
 * the three dimensional position for each point along the line.
 *
 * Trails can be rendered either as lines, as points, or a combination of both with
 * varying colors, line thicknesses, or fading settings. If trails are rendered as points,
 * the RenderInformation's `stride` parameter determines the number of points between
 * larger points. A potential use case for this is showing the passage of time along a
 * trail by using a point separation of one hour and a subsampling of 4, you would get a
 * point every 15 minutes with every hourly point being bigger.
 *
 * The positions for each point along the trail is provided through a Translation object,
 * the type of which is specified in the dictionary that is passed to the constructor. A
 * typical implementation of Translation used for the trail would be a SpiceTranslation.
 */
class RenderableTrail : public Renderable {
public:
    const double DISTANCE_CULLING_RADII = 800.0;

    struct Appearance : properties::PropertyOwner {
        Appearance();

        /// Specifies the base color of the line before fading
        properties::Vec3Property lineColor;
        /// Settings that enables or disables the line fading
        properties::BoolProperty useLineFade;
        /// Line width for the line rendering part
        properties::FloatProperty lineWidth;
        /// Point size for the point rendering part
        properties::IntProperty pointSize;
        /// The option determining which rendering method to use
        properties::OptionProperty renderingModes;
        /// Specifies how much of the orbit should have a trail
        properties::FloatProperty lineLength;
        /// Specifies how much of the trail should be faded
        properties::FloatProperty lineFadeAmount;
    };

    virtual ~RenderableTrail() override = default;

    void initialize() override;
    void initializeGL() override;
    void deinitializeGL() override;

    bool isReady() const override;

    /**
     * The render method will set up the shader information and then render first the
     * information contained in the the `_primaryRenderInformation`, then the optional
     * `_floatingRenderInformation` using the provided \p data.
     *
     * \param data The data that is necessary to render this Renderable
     * \param rendererTask A place to store render tasks from this Renderable
     */
    void render(const RenderData& data, RendererTasks& rendererTask) override;

protected:
    explicit RenderableTrail(const ghoul::Dictionary& dictionary);

    /**
     * Get the trail position for a given time from the Translation object. The position
     * will be in the local coordinate system of the renderable.
     *
     * \param time The time for which to get the position
     * \return The position of the trail at the given time, in the local coordinate system
     */
    glm::dvec3 translationPosition(Time time) const;

    static documentation::Documentation Documentation();

    /// The layout of the VBOs (use float if sending as positions to shader)
    template <typename T>
    struct TrailVBOLayout {
        T x, y, z;
    };

    /// The backend storage for the vertex buffer object containing all points for this
    /// trail.
    std::vector<TrailVBOLayout<float>> _vertexArray;

    /// The index array that is potentially used in the draw call. If this is empty, no
    /// element draw call is used.
    std::vector<unsigned int> _indexArray;

    /// The Translation object that provides the position of the individual trail points
    ghoul::mm_unique_ptr<Translation> _translation;

    /**
     * The RenderInformation contains information filled in by the concrete subclasses to
     * be used by this class.
     */
    struct RenderInformation {
        enum class VertexSorting {
            /// Newer vertices have a lower index than older ones
            NewestFirst = 0,
            /// Older vertices have a lower index than newer ones
            OldestFirst,
            /// No ordering in the vertices; no fading applied
            NoSorting
        };
        /// The first element in the vertex buffer to be rendered
        GLint first = 0;
        /// The number of values to be rendered
        GLsizei count = 0;
        /// The stride between 'major' points in the array
        int stride = 1;
        /// Sorting of the vertices; required for correct fading
        VertexSorting sorting = VertexSorting::NoSorting;

        /// Local model matrix transformation, used for rendering in camera space
        glm::dmat4 _localTransform = glm::dmat4(1.0);

        /// The vertex array object for this RenderInformation
        GLuint _vaoID = 0;
        /// The main vertex buffer object
        GLuint _vBufferID = 0;
        /// The optional index buffer object
        GLuint _iBufferID = 0;
    };

    /// Primary set of information about the main rendering parts
    RenderInformation _primaryRenderInformation;
    /// Optional render information that contains information about the last, floating
    /// part of the trail
    RenderInformation _floatingRenderInformation;
    /// Render information that contains information about trail segments after the
    /// object point (renderableTrailTrajectory)
    RenderInformation _secondaryRenderInformation;

    /// Flag used to determine if we use a split trail or not during rendering
    bool _useSplitRenderMode = false;
    /// Number of unique vertices used when rendering segmented trails
    int _nUniqueVertices = 0;

private:
    void internalRender(bool renderLines, bool renderPoints,
        const RenderData& data,
        const glm::dmat4& modelTransform,
        RenderInformation& info, int nVertices, int ringOffset,
        bool useSplitRenderMode = false, int numberOfUniqueVertices = 0,
        int floatingOffset = 0);

   Appearance _appearance;

    /// Program object used to render the data stored in RenderInformation
    ghoul::opengl::ProgramObject* _programObject = nullptr;
#ifdef __APPLE__
    UniformCache(opacity, modelViewTransform, projectionTransform, color, useLineFade,
        lineLength, lineFadeAmount, vertexSortingMethod, idOffset, nVertices, stride,
        pointSize, renderPhase, useSplitRenderMode, floatingOffset, numberOfUniqueVertices
    ) _uniformCache;
#else
    UniformCache(opacity, modelViewTransform, projectionTransform, color, useLineFade,
        lineLength, lineFadeAmount, vertexSortingMethod, idOffset, nVertices, stride,
        pointSize, renderPhase, viewport, lineWidth, floatingOffset, useSplitRenderMode,
        numberOfUniqueVertices
    ) _uniformCache;
#endif
};

} // namespace openspace

#endif // __OPENSPACE_MODULE_BASE___RENDERABLETRAIL___H__