convex y-aligned prism intersection checking

docs/src/progress/renderertodo.md

@@ -2033,6 +2033,7 @@ Fix physics destruction on server via ServerLODComponent
 More job data scaffolding
 Config class cleanup
 Fix jobs data, simplify block chunk gen algo
+Convex y-aligned prism intersection checking
 
 
 

src/main/java/electrosphere/util/math/GeomUtils.java

@@ -688,5 +688,41 @@ public class GeomUtils {
         }
         return false;
     }
+
+    /**
+     * Checks if a point falls within a prism or not
+     * @param point The point
+     * @param prismPoints The points defining the base of the prism
+     * @return true if the point is within the prism, false otherwise
+     */
+    public static boolean pointIntersectsConvexPrism(Vector3d point, Vector3d[] prismPoints, double height){
+        //error check quad definition
+        if(height <= 0){
+            throw new Error("Quad has invalid height! " + height);
+        }
+        if(prismPoints.length < 3){
+            throw new Error("Too few points! " + prismPoints.length);
+        }
+        //make sure the base is on the same y level
+        for(int i = 1; i < prismPoints.length; i++){
+            if(prismPoints[i].y != prismPoints[0].y){
+                throw new Error("Quadrilateral isn't aligned along y axis " + prismPoints[0].y + " " + prismPoints[i].y + " " + i);
+            }
+        }
+        //outside of y-bounds
+        if(point.y < prismPoints[0].y || point.y > prismPoints[0].y + height){
+            return false;
+        }
+        //check if the point is within the x-z quadrilaterial
+        int crossings = 0;
+        for(int i = 0; i < prismPoints.length; i++){
+            Vector3d point1 = prismPoints[i];
+            Vector3d point2 = prismPoints[(i + 1) % prismPoints.length];
+            if (((point1.z > point.z) != (point2.z > point.z)) && (point.x < (point2.x - point1.x) * (point.z - point1.z) / (point2.z - point1.z) + point1.x)) {
+                crossings++;
+            }
+        }
+        return (crossings % 2 == 1);
+    }
     
 }

src/test/java/electrosphere/util/math/GeomUtilsTests.java

@@ -112,4 +112,72 @@ public class GeomUtilsTests {
         assertTrue(GeomUtils.pointIntersectsSpline(new Vector3d(524298.0,10,524288.0), testSpline, 3));
     }
 
+    @UnitTest
+    public void test_pointIntersectsConvexPrism_1(){
+        //prism
+        Vector3d[] basePoints = new Vector3d[]{
+            new Vector3d(0,0,0),
+            new Vector3d(3,0,10),
+            new Vector3d(10,0,10),
+            new Vector3d(10,0,7),
+        };
+        double height = 2;
+
+        //point
+        Vector3d testPt = new Vector3d(5,1,5);
+
+        assertTrue(GeomUtils.pointIntersectsConvexPrism(testPt, basePoints, height));
+    }
+
+    @UnitTest
+    public void test_pointIntersectsConvexPrism_2(){
+        //prism
+        Vector3d[] basePoints = new Vector3d[]{
+            new Vector3d(0,0,0),
+            new Vector3d(3,0,10),
+            new Vector3d(10,0,10),
+            new Vector3d(10,0,7),
+        };
+        double height = 2;
+
+        //point
+        Vector3d testPt = new Vector3d(10,1,5);
+
+        assertFalse(GeomUtils.pointIntersectsConvexPrism(testPt, basePoints, height));
+    }
+
+    @UnitTest
+    public void test_pointIntersectsConvexPrism_3(){
+        //prism
+        Vector3d[] basePoints = new Vector3d[]{
+            new Vector3d(0,0,0),
+            new Vector3d(3,0,10),
+            new Vector3d(10,0,10),
+            new Vector3d(10,0,7),
+        };
+        double height = 2;
+
+        //point
+        Vector3d testPt = new Vector3d(10,5,5);
+
+        assertFalse(GeomUtils.pointIntersectsConvexPrism(testPt, basePoints, height));
+    }
+
+    @UnitTest
+    public void test_pointIntersectsConvexPrism_4(){
+        //prism
+        Vector3d[] basePoints = new Vector3d[]{
+            new Vector3d(0,0,0),
+            new Vector3d(3,0,10),
+            new Vector3d(10,0,10),
+            new Vector3d(10,0,7),
+        };
+        double height = 2;
+
+        //point
+        Vector3d testPt = new Vector3d(10,-1,5);
+
+        assertFalse(GeomUtils.pointIntersectsConvexPrism(testPt, basePoints, height));
+    }
+
 }