feat: standardize NODATA values to Float.NaN

Author: znkim

mago-terrainer/src/main/java/com/gaia3d/terrain/tile/raster/TerrainRasterFormat.java

@@ -12,6 +12,7 @@ public final class TerrainRasterFormat {
     public static final int VERSION = 1;
     public static final int HEADER_SIZE_BYTES = 64;
     public static final int FLOAT_BYTES = Float.BYTES;
+    public static final float NO_DATA_VALUE = Float.NaN;
     public static final ByteOrder BYTE_ORDER = ByteOrder.LITTLE_ENDIAN;
 
 }

mago-terrainer/src/main/java/com/gaia3d/terrain/tile/raster/TerrainRasterWriter.java

@@ -31,16 +31,19 @@ public void write(Path path, GridCoverage2D coverage) throws IOException {
         Raster raster = coverage.getRenderedImage().getData();
         int width = raster.getWidth();
         int height = raster.getHeight();
-        float sourceNoDataValue = resolveNoDataValue(coverage);
-        float noDataValue = (float) GlobalOptions.getInstance().getNoDataValue();
+        double sourceNoDataValue = resolveNoDataValue(coverage);
+        double configuredNoDataValue = GlobalOptions.getInstance().getNoDataValue();
+        float noDataValue = TerrainRasterFormat.NO_DATA_VALUE;
         float[] elevations = new float[Math.multiplyExact(width, height)];
         int index = 0;
         int maxX = raster.getMinX() + width;
         int maxY = raster.getMinY() + height;
         for (int y = raster.getMinY(); y < maxY; y++) {
             for (int x = raster.getMinX(); x < maxX; x++) {
                 double sample = raster.getSampleDouble(x, y, 0);
-                elevations[index++] = isNoData(sample, sourceNoDataValue) ? noDataValue : (float) sample;
+                float elevation = (float) sample;
+                elevations[index++] = isNoData(sample, sourceNoDataValue, configuredNoDataValue) || !Float.isFinite(elevation)
+                        ? noDataValue : elevation;
             }
         }
 
@@ -51,14 +54,19 @@ public void write(Path path, GridCoverage2D coverage) throws IOException {
                 noDataValue, elevations));
     }
 
-    private float resolveNoDataValue(GridCoverage2D coverage) {
+    private double resolveNoDataValue(GridCoverage2D coverage) {
         NoDataContainer noData = CoverageUtilities.getNoDataProperty(coverage);
-        return noData == null ? Float.NaN : (float) noData.getAsSingleValue();
+        return noData == null ? Double.NaN : noData.getAsSingleValue();
     }
 
-    private boolean isNoData(double sample, float sourceNoDataValue) {
+    private boolean isNoData(double sample, double sourceNoDataValue, double configuredNoDataValue) {
         return !Double.isFinite(sample)
-                || (!Float.isNaN(sourceNoDataValue) && Double.compare(sample, sourceNoDataValue) == 0);
+                || matchesNoData(sample, sourceNoDataValue)
+                || matchesNoData(sample, configuredNoDataValue);
+    }
+
+    private boolean matchesNoData(double sample, double noDataValue) {
+        return !Double.isNaN(noDataValue) && Double.compare(sample, noDataValue) == 0;
     }
 
     private ByteBuffer createHeader(TerrainRasterData data) {

mago-terrainer/src/test/java/com/gaia3d/terrain/tile/raster/TerrainRasterReaderWriterTest.java

@@ -1,5 +1,6 @@
 package com.gaia3d.terrain.tile.raster;
 
+import com.gaia3d.command.GlobalOptions;
 import com.gaia3d.terrain.tile.core.*;
 import com.gaia3d.terrain.tile.elevation.*;
 import com.gaia3d.terrain.tile.generation.*;
@@ -8,16 +9,56 @@
 
 import org.junit.jupiter.api.Tag;
 import org.junit.jupiter.api.Test;
-
+import org.eclipse.imagen.PlanarImage;
+import org.eclipse.imagen.RasterFactory;
+import org.eclipse.imagen.TiledImage;
+import org.eclipse.imagen.media.range.NoDataContainer;
+import org.geotools.coverage.grid.GridCoverage2D;
+import org.geotools.coverage.grid.GridCoverageFactory;
+import org.geotools.coverage.util.CoverageUtilities;
+import org.geotools.geometry.jts.ReferencedEnvelope;
+import org.geotools.referencing.crs.DefaultGeographicCRS;
+
+import java.awt.image.DataBuffer;
+import java.awt.image.WritableRaster;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.HashMap;
+import java.util.Map;
 
 import static org.junit.jupiter.api.Assertions.*;
 
 class TerrainRasterReaderWriterTest {
 
+    @Test
+    @Tag("default")
+    void coverageWriterPreservesDoubleNoDataMarkerForComparison() throws Exception {
+        Path tempDir = Files.createTempDirectory("terrain-raster-double-nodata-");
+        Path rasterPath = tempDir.resolve("tile" + TerrainRasterFormat.EXTENSION);
+        GlobalOptions globalOptions = GlobalOptions.getInstance();
+        double previousNoData = globalOptions.getNoDataValue();
+        globalOptions.setNoDataValue(-9999.0);
+        GridCoverage2D coverage = createDoubleCoverage(
+                new double[]{-Double.MAX_VALUE, -9999.0, Double.NaN, 123.5}, -Double.MAX_VALUE);
+
+        try {
+            new TerrainRasterWriter().write(rasterPath, coverage);
+            TerrainRasterData read = new TerrainRasterReader().read(rasterPath);
+
+            assertTrue(Float.isNaN(read.noDataValue()));
+            assertTrue(Float.isNaN(read.getElevation(0, 0)));
+            assertTrue(Float.isNaN(read.getElevation(1, 0)));
+            assertTrue(Float.isNaN(read.getElevation(2, 0)));
+            assertEquals(123.5f, read.getElevation(3, 0));
+        } finally {
+            coverage.dispose(true);
+            globalOptions.setNoDataValue(previousNoData);
+            deleteRecursively(tempDir);
+        }
+    }
+
     @Test
     @Tag("default")
     void writerAndReaderRoundTripFloat32TerrainRaster() throws Exception {
@@ -108,6 +149,21 @@ void publicRasterDataConstructorRetainsDefensiveCopy() {
         assertEquals(10.0f, data.getElevation(0, 0));
     }
 
+    private GridCoverage2D createDoubleCoverage(double[] values, double noDataValue) {
+        WritableRaster raster = RasterFactory.createBandedRaster(DataBuffer.TYPE_DOUBLE, values.length, 1, 1, null);
+        for (int x = 0; x < values.length; x++) {
+            raster.setSample(x, 0, 0, values[x]);
+        }
+
+        TiledImage image = new TiledImage(0, 0, values.length, 1, 0, 0,
+                raster.getSampleModel(), PlanarImage.createColorModel(raster.getSampleModel()));
+        image.setData(raster);
+        Map<String, Object> properties = new HashMap<>();
+        CoverageUtilities.setNoDataProperty(properties, new NoDataContainer(noDataValue));
+        ReferencedEnvelope envelope = new ReferencedEnvelope(0.0, values.length, 0.0, 1.0, DefaultGeographicCRS.WGS84);
+        return new GridCoverageFactory().create("double-dem", image, envelope, null, null, properties);
+    }
+
     private void deleteRecursively(Path path) throws IOException {
         if (!Files.exists(path)) {
             return;