Fix reflection on transparent areas of glass panes.

Author: leMaik

chunky/src/java/se/llbit/chunky/model/minecraft/GlassPaneModel.java

@@ -173,4 +173,53 @@ public Quad[] getQuads() {
   public Texture[] getTextures() {
     return textures;
   }
+
+  /**
+   * Intersects this glass pane model with the given ray.
+   * <p>
+   * Unlike {@link QuadModel#intersect(Ray, Scene)}, this method also registers
+   * hits in the transparent regions of the quads. In addition, biome tinting is
+   * disabled as a minor optimization, since it does not affect glass panes.
+   *
+   * @param ray   the ray to test for intersection
+   * @param scene the scene providing context for the intersection
+   * @return true if the glass pane was hit, false otherwise
+   */
+  @Override
+  public boolean intersect(Ray ray, Scene scene) {
+    boolean hit = false;
+    ray.t = Double.POSITIVE_INFINITY;
+
+    Quad[] quads = getQuads();
+    Texture[] textures = getTextures();
+
+    float[] color = null;
+    for (int i = 0; i < quads.length; ++i) {
+      Quad quad = quads[i];
+      if (quad.intersect(ray)) {
+        color = textures[i].getColor(ray.u, ray.v);
+        ray.t = ray.tNext;
+        if (quad.doubleSided)
+          ray.orientNormal(quad.n);
+        else
+          ray.setNormal(quad.n);
+        hit = true;
+      }
+    }
+
+    if (hit) {
+      double px = ray.o.x - Math.floor(ray.o.x + ray.d.x * Ray.OFFSET) + ray.d.x * ray.tNext;
+      double py = ray.o.y - Math.floor(ray.o.y + ray.d.y * Ray.OFFSET) + ray.d.y * ray.tNext;
+      double pz = ray.o.z - Math.floor(ray.o.z + ray.d.z * Ray.OFFSET) + ray.d.z * ray.tNext;
+      if (px < E0 || px > E1 || py < E0 || py > E1 || pz < E0 || pz > E1) {
+        // TODO this check is only really needed for wall torches
+        return false;
+      }
+
+      ray.color.set(color);
+      ray.distance += ray.t;
+      ray.o.scaleAdd(ray.t, ray.d);
+    }
+    return hit;
+  }
 }