Fix water artifact when looking at water on the horizon/with low incidence angle (#935)

* Change all access to ray.n to use getter/setter so we can keep track of the geometry normal and the shading normal at the same time

* Take the real geometry normal into account when computing ray direction for reflection or refraction to not go through the geometry

* Make the code work even if the face faces the other direction.
Copy the vector in setN rather keeping a reference on it (caused issue when the vector was reused by the caller of setN)

* Oops bad rebase (more usage of setN)

* Add function to set and orient ray.n and use it everywhere to save on an allocation (and simplify the code)

* Rename normal related methods and add a bit of javadoc

Author: aTom3333

chunky/src/java/se/llbit/chunky/block/AttachedStem.java

@@ -69,8 +69,7 @@ public AttachedStem(String name, String facing) {
           ray.color.y *= Stem.stemColor[7][1];
           ray.color.z *= Stem.stemColor[7][2];
           ray.t = ray.tNext;
-          ray.n.set(quad.n);
-          ray.n.scale(-QuickMath.signum(ray.d.dot(quad.n)));
+          ray.orientNormal(quad.n);
           hit = true;
         }
       }
@@ -84,8 +83,7 @@ public AttachedStem(String name, String facing) {
         ray.color.y *= Stem.stemColor[7][1];
         ray.color.z *= Stem.stemColor[7][2];
         ray.t = ray.tNext;
-        ray.n.set(quad.n);
-        ray.n.scale(-QuickMath.signum(ray.d.dot(quad.n)));
+        ray.orientNormal(quad.n);
         hit = true;
       }
     }

chunky/src/java/se/llbit/chunky/block/Conduit.java

@@ -55,7 +55,7 @@ public Conduit() {
         float[] color = texture.getColor(ray.u, ray.v);
         if (color[3] > Ray.EPSILON) {
           ray.color.set(color);
-          ray.n.set(quad.n);
+          ray.setNormal(quad.n);
           ray.t = ray.tNext;
           hit = true;
         }

chunky/src/java/se/llbit/chunky/block/GrassBlock.java

@@ -4,6 +4,7 @@
 import se.llbit.chunky.resources.Texture;
 import se.llbit.math.AABB;
 import se.llbit.math.Ray;
+import se.llbit.math.Vector3;
 
 public class GrassBlock extends MinecraftBlock {
   private final static AABB aabb = new AABB(0, 1, 0, 1, 0, 1);
@@ -16,13 +17,14 @@ public GrassBlock() {
   @Override public boolean intersect(Ray ray, Scene scene) {
     ray.t = Double.POSITIVE_INFINITY;
     if (aabb.intersect(ray)) {
-      if (ray.n.y == -1) {
+      Vector3 n = ray.getNormal();
+      if (n.y == -1) {
         // Bottom face.
         Texture.dirt.getColor(ray);
         ray.t = ray.tNext;
       } else {
         float[] color;
-        if (ray.n.y > 0) {
+        if (n.y > 0) {
           color = Texture.grassTop.getColor(ray.u, ray.v);
         } else {
           color = Texture.grassSide.getColor(ray.u, ray.v);

chunky/src/java/se/llbit/chunky/block/Lava.java

@@ -58,8 +58,7 @@ public boolean isFullBlock() {
 
     boolean hit = false;
     if (bottom.intersect(ray)) {
-      ray.n.set(bottom.n);
-      ray.n.scale(-QuickMath.signum(ray.d.dot(bottom.n)));
+      ray.orientNormal(bottom.n);
       ray.t = ray.tNext;
       hit = true;
     }
@@ -70,24 +69,21 @@ public boolean isFullBlock() {
     int c3 = (0xF & (data >> CORNER_3)) % 8;
     Triangle triangle = Water.t012[c0][c1][c2];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       hit = true;
     }
     triangle = Water.t230[c2][c3][c0];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       ray.u = 1 - ray.u;
       ray.v = 1 - ray.v;
       hit = true;
     }
     triangle = Water.westt[c0][c3];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       double y = ray.t * ray.d.y + ray.o.y;
       double z = ray.t * ray.d.z + ray.o.z;
@@ -99,8 +95,7 @@ public boolean isFullBlock() {
     }
     triangle = Water.westb[c0];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       double y = ray.t * ray.d.y + ray.o.y;
       double z = ray.t * ray.d.z + ray.o.z;
@@ -112,8 +107,7 @@ public boolean isFullBlock() {
     }
     triangle = Water.eastt[c1][c2];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       double y = ray.t * ray.d.y + ray.o.y;
       double z = ray.t * ray.d.z + ray.o.z;
@@ -125,8 +119,7 @@ public boolean isFullBlock() {
     }
     triangle = Water.eastb[c1];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       double y = ray.t * ray.d.y + ray.o.y;
       double z = ray.t * ray.d.z + ray.o.z;
@@ -138,8 +131,7 @@ public boolean isFullBlock() {
     }
     triangle = Water.southt[c0][c1];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       double x = ray.t * ray.d.x + ray.o.x;
       double y = ray.t * ray.d.y + ray.o.y;
@@ -151,8 +143,7 @@ public boolean isFullBlock() {
     }
     triangle = Water.southb[c1];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       double x = ray.t * ray.d.x + ray.o.x;
       double y = ray.t * ray.d.y + ray.o.y;
@@ -164,8 +155,7 @@ public boolean isFullBlock() {
     }
     triangle = Water.northt[c2][c3];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       double x = ray.t * ray.d.x + ray.o.x;
       double y = ray.t * ray.d.y + ray.o.y;
@@ -177,8 +167,7 @@ public boolean isFullBlock() {
     }
     triangle = Water.northb[c2];
     if (triangle.intersect(ray)) {
-      ray.n.set(triangle.n);
-      ray.n.scale(QuickMath.signum(-ray.d.dot(triangle.n)));
+      ray.orientNormal(triangle.n);
       ray.t = ray.tNext;
       double x = ray.t * ray.d.x + ray.o.x;
       double y = ray.t * ray.d.y + ray.o.y;

chunky/src/java/se/llbit/chunky/block/Log.java

@@ -81,7 +81,7 @@ public Log(String name, Texture side, Texture top, String axis) {
         ray.u = (1 - uv_x) * ray.u + uv_x * ray.v;
         ray.v = uv_x * u + (1 - uv_x) * ray.v;
         texture[textureIndex[direction][i]].getColor(ray);
-        ray.n.set(side.n);
+        ray.setNormal(side.n);
         ray.t = ray.tNext;
         hit = true;
       }

chunky/src/java/se/llbit/chunky/block/NetherPortal.java

@@ -49,7 +49,7 @@ public NetherPortal(String axis) {
       return false;
     }
     texture.getColor(ray);
-    ray.n.set(quad[axis].n);
+    ray.setNormal(quad[axis].n);
     ray.t = ray.tNext;
     ray.distance += ray.t;
     ray.o.scaleAdd(ray.t, ray.d);

chunky/src/java/se/llbit/chunky/block/OrientedTexturedBlock.java

@@ -105,7 +105,7 @@ public boolean intersect(Ray ray, Scene scene) {
       if (side.intersect(ray)) {
         rotateUV(ray, i);
         texture[textureOrientationMap[facing][i]].getColor(ray);
-        ray.n.set(side.n);
+        ray.setNormal(side.n);
         ray.t = ray.tNext;
         hit = true;
       }

chunky/src/java/se/llbit/chunky/block/SeaPickle.java

@@ -730,7 +730,7 @@ public boolean intersect(Ray ray, Scene scene) {
         if (color[3] > Ray.EPSILON) {
           ray.color.set(color);
           texture.getColor(ray);
-          ray.n.set(quad.n);
+          ray.setNormal(quad.n);
           ray.t = ray.tNext;
           hit = true;
         }
@@ -742,7 +742,7 @@ public boolean intersect(Ray ray, Scene scene) {
           float[] color = texture.getColor(ray.u, ray.v);
           if (color[3] > Ray.EPSILON) {
             ray.color.set(color);
-            ray.n.set(quad.n);
+            ray.setNormal(quad.n);
             ray.t = ray.tNext;
             hit = true;
           }

chunky/src/java/se/llbit/chunky/block/Slab.java

@@ -50,7 +50,7 @@ public Slab(String name, Texture texture, String type) {
   @Override public boolean intersect(Ray ray, Scene scene) {
     ray.t = Double.POSITIVE_INFINITY;
     if (aabb[half].intersect(ray)) {
-      if (ray.n.y != 0) {
+      if (ray.getNormal().y != 0) {
         topTexture.getColor(ray);
       } else {
         sideTexture.getColor(ray);

chunky/src/java/se/llbit/chunky/block/SnowCovered.java

@@ -3,6 +3,7 @@
 import se.llbit.chunky.renderer.scene.Scene;
 import se.llbit.chunky.resources.Texture;
 import se.llbit.math.Ray;
+import se.llbit.math.Vector3;
 
 public class SnowCovered extends MinecraftBlock {
   private final Block block;
@@ -17,9 +18,10 @@ public SnowCovered(Block block) {
     ray.t = Double.POSITIVE_INFINITY;
     boolean hit = block.intersect(ray, scene);
     if (hit) {
-      if (ray.n.y == 0) {
+      Vector3 n = ray.getNormal();
+      if (n.y == 0) {
         Texture.snowSide.getColor(ray);
-      } else if (ray.n.y > 0) {
+      } else if (n.y > 0) {
         Texture.snowBlock.getColor(ray);
       }
     }