195 lines
8.9 KiB
C
195 lines
8.9 KiB
C
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#pragma once
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#include "Library.h"
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#include "RasterOverlayDetails.h"
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#include <CesiumGeometry/QuadtreeTileID.h>
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#include <CesiumGeospatial/Ellipsoid.h>
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#include <CesiumGeospatial/Projection.h>
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#include <glm/fwd.hpp>
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#include <optional>
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#include <string_view>
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#include <vector>
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namespace CesiumGltf {
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struct Model;
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}
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namespace CesiumRasterOverlays {
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/**
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* @brief A collection of utilities useful for operations involving raster
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* overlay tiles.
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*/
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struct CESIUMRASTEROVERLAYS_API RasterOverlayUtilities {
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/**
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* @brief Texture coordinates will be stored in the glTF under the following
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* name, appended with a number. See \ref
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* createRasterOverlayTextureCoordinates.
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*/
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static constexpr std::string_view DEFAULT_TEXTURE_COORDINATE_BASE_NAME =
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"_CESIUMOVERLAY_";
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/**
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* @brief Creates texture coordinates for mapping {@link RasterOverlay} tiles
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* to a glTF model.
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*
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* Generates new texture coordinates for the `gltf` using the given
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* `projections`. The first new texture coordinate (`u` or `s`) will be 0.0 at
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* the `minimumX` of the given `rectangle` and 1.0 at the `maximumX`. The
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* second texture coordinate (`v` or `t`) will be 0.0 at the `minimumY` of
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* the given `rectangle` and 1.0 at the `maximumY`.
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*
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* Coordinate values for vertices in between these extremes are determined by
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* projecting the vertex position with the `projection` and then computing the
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* fractional distance of that projected position between the minimum and
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* maximum.
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*
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* Projected positions that fall outside the `globeRectangle` will be clamped
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* to the edges, so the coordinate values will never be less then 0.0 or
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* greater than 1.0.
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*
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* These texture coordinates are stored in the provided glTF, and a new
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* primitive attribute is added to each primitive for each projection. The new
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* primitive attributes are named with `textureCoordinateAttributeBaseName`
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* followed by a number, starting with `firstTextureCoordinateID` and
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* incrementing for each projection. For example, if
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* `textureCoordinateAttributeBaseName` is
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* `_CESIUMOVERLAY_` and `firstTextureCoordinateID` is 0 (the defaults), then
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* the texture coordinates for the first projection will be stored in an
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* attribute named `_CESIUMOVERLAY_0`, the second will be in
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* `_CESIUMOVERLAY_1`, and so on.
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*
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* @param gltf The glTF model.
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* @param modelToEcefTransform The transformation of this glTF to ECEF
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* coordinates.
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* @param globeRectangle The rectangle that all projected vertex positions are
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* expected to lie within. If this parameter is std::nullopt, it is computed
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* from the vertices.
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* @param projections The projections for which to generate texture
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* coordinates. There is a linear relationship between the coordinates of this
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* projection and the generated texture coordinates.
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* @param invertVCoordinate True if the V texture coordinate should be
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* inverted so that it is 1.0 at the Southern end of the rectangle and 0.0 at
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* the Northern end. This is useful with images that use the typical North-up
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* orientation.
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* @param textureCoordinateAttributeBaseName The base name to use for the
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* texture coordinate attributes, without a number on the end. Defaults to
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* {@link DEFAULT_TEXTURE_COORDINATE_BASE_NAME}.
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* @param firstTextureCoordinateID The texture coordinate ID of the first
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* projection.
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* @return The details of the generated texture coordinates.
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*/
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static std::optional<RasterOverlayDetails>
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createRasterOverlayTextureCoordinates(
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CesiumGltf::Model& gltf,
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const glm::dmat4& modelToEcefTransform,
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const std::optional<CesiumGeospatial::GlobeRectangle>& globeRectangle,
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std::vector<CesiumGeospatial::Projection>&& projections,
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bool invertVCoordinate = false,
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const std::string_view& textureCoordinateAttributeBaseName =
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DEFAULT_TEXTURE_COORDINATE_BASE_NAME,
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int32_t firstTextureCoordinateID = 0);
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/**
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* @brief Creates a new glTF model from one of the quadtree children of the
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* given parent model.
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*
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* The parent model subdivision is guided by texture coordinates. These
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* texture coordinates must follow a map projection, and the parent tile is
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* divided into quadrants as divided by this map projection. To create the
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* necessary texture coordinates, use
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* {@link createRasterOverlayTextureCoordinates}.
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*
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* @param parentModel The parent model to upsample.
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* @param childID The quadtree tile ID of the child model. This is used to
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* determine which of the four children of the parent tile to generate.
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* @param hasInvertedVCoordinate True if the V texture coordinate has 0.0 as
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* the Northern-most coordinate; False if the V texture coordinate has 0.0 as
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* the Southern-most coordiante.
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* @param textureCoordinateAttributeBaseName The base name of the attribute
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* that holds the projected texture coordinates. The `textureCoordinateIndex`
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* is appended to this name. Defaults to
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* {@link DEFAULT_TEXTURE_COORDINATE_BASE_NAME}.
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* @param textureCoordinateIndex The index of the texture coordinate set to
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* use. For example, if `textureCoordinateAttributeBaseName` is
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* `_CESIUMOVERLAY_` and this parameter is 0 (the defaults), then the texture
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* coordinates are read from a vertex attribute named `_CESIUMOVERLAY_0`.
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* @param ellipsoid The {@link CesiumGeospatial::Ellipsoid}.
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* @return The upsampled model.
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*/
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static std::optional<CesiumGltf::Model> upsampleGltfForRasterOverlays(
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const CesiumGltf::Model& parentModel,
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CesiumGeometry::UpsampledQuadtreeNode childID,
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bool hasInvertedVCoordinate = false,
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const std::string_view& textureCoordinateAttributeBaseName =
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DEFAULT_TEXTURE_COORDINATE_BASE_NAME,
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int32_t textureCoordinateIndex = 0,
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const CesiumGeospatial::Ellipsoid& ellipsoid =
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CesiumGeospatial::Ellipsoid::WGS84);
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/**
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* @brief Computes the desired screen pixels for a raster overlay texture.
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*
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* This method is used to determine the appropriate number of "screen pixels"
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* to use for a raster overlay texture to be attached to a glTF (which is
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* usually a 3D Tiles tile). In other words, how detailed should the texture
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* be? The answer depends, of course, on how close we'll get to the model. If
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* we're going to get very close, we'll need a higher-resolution raster
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* overlay texture than if we will stay far away from it.
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*
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* In 3D Tiles, we can only get so close to a model before it switches to the
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* next higher level-of-detail by showing its children instead. The switch
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* distance is controlled by the `geometric error` of the tile, as well as by
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* the `maximum screen space error` of the tileset. So this method requires
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* both of those parameters.
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*
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* The answer also depends on the size of the model on the screen at this
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* switch distance. To determine that, this method takes a projection and a
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* rectangle that bounds the tile, expressed in that projection. This
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* rectangle is projected onto the screen at the switch distance, and the size
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* of that rectangle on the screen is the `target screen pixels` returned by
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* this method.
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*
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* The `target screen pixels` returned here may be further modified by the
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* raster overlay's {@link RasterOverlayTileProvider::getTile} method. In particular, it
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* will usually be divided by the raster overlay's `maximum screen space
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* error` of the raster overlay (not to be confused with the `maximum screen
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* space error` of the tileset, mentioned above).
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*
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* @param geometricError The geometric error of the tile.
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* @param maximumScreenSpaceError The maximum screen-space error used to
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* render the tileset.
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* @param projection The projection in which the `rectangle` parameter is
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* provided.
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* @param rectangle The 2D extent of the tile, expressed in the `projection`.
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* @param ellipsoid The ellipsoid with which computations are performed.
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* @return The desired screen pixels.
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*/
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static glm::dvec2 computeDesiredScreenPixels(
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double geometricError,
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double maximumScreenSpaceError,
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const CesiumGeospatial::Projection& projection,
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const CesiumGeometry::Rectangle& rectangle,
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const CesiumGeospatial::Ellipsoid& ellipsoid CESIUM_DEFAULT_ELLIPSOID);
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/**
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* @brief Computes the texture translation and scale necessary to align a
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* raster overlay with the given rectangle on geometry whose texture
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* coordinates were computed using a different rectangle.
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*
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* @param geometryRectangle The geometry rectangle used to the compute the
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* texture coordinates.
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* @param overlayRectangle The rectangle covered by the raster overlay
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* texture.
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* @return The translation in X and Y, and the scale in Z and W.
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*/
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static glm::dvec4 computeTranslationAndScale(
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const CesiumGeometry::Rectangle& geometryRectangle,
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const CesiumGeometry::Rectangle& overlayRectangle);
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};
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} // namespace CesiumRasterOverlays
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