1 files changed, 24 insertions, 0 deletions
diff --git a/resources/shaders/algorithms/normal.frag b/resources/shaders/algorithms/normal.frag
new file mode 100644
index 0000000..0f61544
--- /dev/null
+++ b/resources/shaders/algorithms/normal.frag
@@ -0,0 +1,24 @@
+// Requirements:
+// #define NORMAL_ACCURACY 0.01
+// GetDist: (vec3 position) => float
+// GetDist should return the closest object point distance from position (in the whole scene)
+
+/**
+ * Compute the normal of an object at a given surface point
+ * this can be usefull for lighting etc..
+ * This function exploit the fact that the gradient on a given surface point in 3D space
+ * given the normal direction (source: https://fr.wikipedia.org/wiki/Gradient#Dimension_3_:_gradient_normal_%C3%A0_une_surface_en_un_point,_plan_tangent)
+ * 
+ * 
+ */
+vec3 GetNormal(vec3 point_position) {
+	float point_distance = GetDist(point_position);
+    vec2 epsilon = vec2(NORMAL_ACCURACY, 0); // Just a convenient way to use NORMAL_ACCURACY and 0
+    // Compute the gradient
+    vec3 gradient = point_distance - vec3(
+        GetDist(point_position-epsilon.xyy),
+        GetDist(point_position-epsilon.yxy),
+        GetDist(point_position-epsilon.yyx));
+    
+    return normalize(gradient);
+}
+\ No newline at end of file