Fixed some bias issues

Author: PearCoding

scenes/many_point_lights_scene.json

@@ -1,7 +1,8 @@
 {
 	"technique": {
 		"type": "path",
-		"max_depth": 64
+		"max_depth": 64,
+		"light_selector": "simple"
 	},
 	"camera": {
 		"type": "perspective",

src/artic/impl/light_hierarchy.art

@@ -47,13 +47,13 @@ mod light_hierarchy {
             1:f32
         }; 
 
-        entry.flux * cos_d / math_builtins::fmax[f32](0.0001, dist2)
+        all::safe_div(entry.flux * cos_d, dist2)
     }
 
     fn @get_left_prop(left: LightHierarchyEntry, right: LightHierarchyEntry, pos: Vec3) -> f32 {
         let cl = get_entry_cost(left, pos);
         let cr = get_entry_cost(right, pos);
-        cl / (cl + cr)
+        1 / (1 + cr/cl)
     }
 
     fn @random_select_left(rnd: &mut RndState, left: LightHierarchyEntry, right: LightHierarchyEntry, pos: Vec3) -> (bool, f32) {
@@ -65,9 +65,11 @@ mod light_hierarchy {
         let mut pdf   = 1:f32;
         let mut entry = load_entry(0, data);
         while !entry.is_leaf {
-            let (is_left, prop) = random_select_left(rnd, load_entry(entry.id, data), load_entry(entry.id+1, data), pos);
+            let left  = load_entry(entry.id, data);
+            let right = load_entry(entry.id+1, data);
+            let (is_left, prop) = random_select_left(rnd, left, right, pos);
 
-            entry = load_entry(all::select(is_left, entry.id, entry.id+1), data);
+            entry = all::select(is_left, left, right);
             pdf  *= all::select(is_left, prop, 1-prop);
         }
 
@@ -82,19 +84,14 @@ mod light_hierarchy {
             let left  = load_entry(entry.id, data);
             let right = load_entry(entry.id+1, data);
             let prop  = get_left_prop(left, right, pos);
+            let is_left = (code & 0x1) == 0;
 
-            if (code & 0x1) == 0 {
-                entry = left;
-                pdf  *= prop;
-            } else {
-                entry = right;
-                pdf  *= 1 - prop;
-            }
-
+            entry  = all::select(is_left, left, right);
+            pdf   *= all::select(is_left, prop, 1-prop);
             code >>= 1;
         }
 
-        all::select(entry.id == light.id, pdf, 0:f32)
+        pdf
     }
 }
 

src/artic/impl/light_selector.art

@@ -47,7 +47,7 @@ fn @make_uniform_light_selector(infinite_lights: LightTable, finite_lights: Ligh
 fn @make_cdf_light_selector(infinite_lights: LightTable, finite_lights: LightTable, sampler: cdf::CDF1D) -> LightSelector {
     if infinite_lights.count == 0 {
         LightSelector {
-            count     = sampler.func_size,
+            count     = finite_lights.count,
             sample    = @|rnd,_| { let s = sampler.sample_discrete(randf(rnd)); (finite_lights.get(s.off), s.pdf) },
             pdf       = @|light,_| sampler.pdf_discrete(light.id).pdf,
             infinites = infinite_lights,
@@ -57,7 +57,7 @@ fn @make_cdf_light_selector(infinite_lights: LightTable, finite_lights: LightTab
         let pdf_infinite_lights = 1 / (infinite_lights.count as f32);
         let infinite_ratio      = 0.5:f32;
         LightSelector {
-            count  = infinite_lights.count + sampler.func_size,
+            count  = infinite_lights.count + finite_lights.count,
             sample = @|rnd,_| {
                 let q = randf(rnd);
                 if q < infinite_ratio {
@@ -92,7 +92,7 @@ fn @make_hierarchy_light_selector(infinite_lights: LightTable, finite_lights: Li
         let infinite_ratio      = 0.5:f32;
         let hierarchy = make_light_hierarchy(finite_lights, data);
         LightSelector {
-            count     = finite_lights.count,
+            count     = infinite_lights.count + finite_lights.count,
             sample    = @|rnd, from_pos| {
                 let q = randf(rnd);
                 if q < infinite_ratio {

src/artic/render/light.art

@@ -97,7 +97,10 @@ struct LightTable {
     get:   fn (i32) -> Light
 }
 
-fn @make_empty_light_table() = LightTable {
-    count = 0,
+/// Set count, but return no valid light. Useful for miss shaders
+fn @make_proxy_light_table(count: i32) = LightTable {
+    count = count,
     get   = @|_| make_null_light(0)
 };
+
+fn @make_empty_light_table() = make_proxy_light_table(0);

src/backend/runtime/loader/LoaderLight.cpp

@@ -109,7 +109,7 @@ std::string LoaderLight::generate(ShadingTree& tree, bool skipFinite)
     stream << generateInfinite(tree);
 
     if (skipFinite)
-        stream << "  let finite_lights = make_empty_light_table();" << std::endl;
+        stream << "  let finite_lights = make_proxy_light_table(" << finiteLightCount() << ");" << std::endl;
     else
         stream << generateFinite(tree);
 
@@ -409,17 +409,20 @@ std::string LoaderLight::generateLightSelector(std::string type, ShadingTree& tr
 {
     const std::string uniformSelector = "  let light_selector = make_uniform_light_selector(infinite_lights, finite_lights);";
 
+    // If there is just a none or just a single light, do not bother with fancy selectors
+    if (lightCount() <= 1)
+        return uniformSelector;
+
     std::stringstream stream;
 
-    const bool fallbackLS = lightCount() <= 1;
-    if (!fallbackLS && type == "hierarchy") {
+    if (type == "hierarchy") {
         auto hierarchy = LightHierarchy::setup(mFiniteLights, tree);
         if (hierarchy.empty()) {
             stream << uniformSelector << std::endl;
         } else {
             stream << "  let light_selector = make_hierarchy_light_selector(infinite_lights, finite_lights, device.load_buffer(\"" << hierarchy.u8string() << "\"));" << std::endl;
         }
-    } else if (!fallbackLS && type == "simple") {
+    } else if (type == "simple") {
         auto cdf = generateLightSelectionCDF(tree);
         if (cdf.empty()) {
             stream << uniformSelector << std::endl;