94 lines
3.4 KiB
Go
94 lines
3.4 KiB
Go
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package svg
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import (
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"fmt"
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"math"
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"strings"
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"b612.me/astro/basic"
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"b612.me/astro/internal/svgmap"
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)
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func transitMapOrthographicCenter(transit basic.PlanetTransitResult) svgmap.GeoPoint {
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if !transit.HasExternal {
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if center, ok := transitMapVisibilityCenter(basic.PlanetTransitVisibilityColumns(transit)); ok {
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return center
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}
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}
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return solarEclipseSubsolarPoint(transitMapContactsOf(transit).greatest)
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}
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func transitMapVisibilityCenter(columns []basic.PlanetTransitVisibilityColumn) (svgmap.GeoPoint, bool) {
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var momentX, momentY, momentZ float64
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for index, column := range columns {
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weight := 0.0
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if index > 0 {
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weight += (column.Longitude - columns[index-1].Longitude) / 2
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}
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if index+1 < len(columns) {
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weight += (columns[index+1].Longitude - column.Longitude) / 2
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}
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longitude := column.Longitude * math.Pi / 180
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for _, interval := range column.Intervals {
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lower, upper := interval[0]*math.Pi/180, interval[1]*math.Pi/180
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horizontalMoment := (upper-lower)/2 + (math.Sin(2*upper)-math.Sin(2*lower))/4
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verticalMoment := (math.Sin(upper)*math.Sin(upper) - math.Sin(lower)*math.Sin(lower)) / 2
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momentX += weight * horizontalMoment * math.Cos(longitude)
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momentY += weight * horizontalMoment * math.Sin(longitude)
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momentZ += weight * verticalMoment
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}
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}
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if math.Sqrt(momentX*momentX+momentY*momentY+momentZ*momentZ) < 1e-12 {
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return svgmap.GeoPoint{}, false
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}
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return svgmap.GeoPoint{
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Longitude: math.Atan2(momentY, momentX) * 180 / math.Pi,
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Latitude: math.Atan2(momentZ, math.Hypot(momentX, momentY)) * 180 / math.Pi,
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}, true
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}
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func transitMapProjectionLabel(projection svgmap.Projection, hasExternal bool, language string) string {
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if projection != svgmap.ProjectionOrthographic {
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return eclipseMapProjectionLabel(projection, language)
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}
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if language == "en" {
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center := "the subsolar point at greatest"
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if !hasExternal {
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center = "the topocentric visible footprint"
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}
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return "Orthographic globe projection, centred on " + center + "; one hemisphere only"
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}
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center := "凌甚太阳直射点"
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if !hasExternal {
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center = "站心可见区中心"
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}
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return "正射球面投影，视点取" + center + "，只画朝向视点的半个地球"
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}
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func writeTransitMapPartialRegions(builder *strings.Builder, frame svgmap.Frame, transit basic.PlanetTransitResult) {
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fmt.Fprintf(builder, `<g class="transit-visibility-regions" data-source="%s" clip-path="url(#transit-map-clip)">`, eclipseMapSourceTransitPartialVisibility)
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var path strings.Builder
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for _, polygon := range basic.PlanetTransitVisibilityPolygons(transit) {
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points := make([]svgmap.GeoPoint, len(polygon))
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for index, point := range polygon {
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points[index] = svgmap.GeoPoint{Longitude: point.Longitude, Latitude: point.Latitude}
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}
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path.WriteString(lunarEclipseGeoPolygonPath(points, frame))
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}
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if path.Len() > 0 {
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fmt.Fprintf(builder, `<path class="transit-partial-region" d="%s" fill="%s" fill-opacity="%.2f" fill-rule="nonzero"/>`, path.String(), transitMapColorPartial, transitMapPartialFillOpacity)
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}
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builder.WriteString(`</g>`)
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}
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func transitMapGeometryNote(transit basic.PlanetTransitResult, language string) string {
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text := fmt.Sprintf("γ %.4f", transit.Gamma)
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if transit.Series.Number != 0 {
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if language == "en" {
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text += fmt.Sprintf(" | Series %d (%d yr)", transit.Series.Number, transit.Series.PeriodYears)
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} else {
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text += fmt.Sprintf(" | 周期族 %d（%d 年）", transit.Series.Number, transit.Series.PeriodYears)
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}
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}
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return text
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}
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