From 568f2450eb03329e6f5c58b5da93877367e508e1 Mon Sep 17 00:00:00 2001
From: Nico de Poel <ndepoel@gmail.com>
Date: Wed, 25 Jan 2023 11:40:10 +0100
Subject: [PATCH] Added a new lighting sampler to take advantage of the
 improved lightmap indexing: use a pseudo-random jitter pattern to take
 multiple light samples in an area around the sample point, from all
 surrounding faces at a shallow angle. This further smooths out the lighting
 and reduces artifacts, while also better representing each face's entire
 lightmap.

---
 bsp.h        | 34 +++++++++++++++++++++++++++++++---
 lighting.cpp | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 lighting.h   |  1 +
 main.cpp     |  2 +-
 4 files changed, 81 insertions(+), 4 deletions(-)

diff --git a/bsp.h b/bsp.h
index f954e57..97447e0 100644
--- a/bsp.h
+++ b/bsp.h
@@ -35,13 +35,42 @@ typedef struct                 // The BSP file header
                                  // nummodels = Size/sizeof(model_t)
 } dheader_t;
 
-typedef struct
+typedef struct Plane
 {
     vec3_t normal;               // Vector orthogonal to plane (Nx,Ny,Nz)
                                 // with Nx2+Ny2+Nz2 = 1
     scalar_t dist;               // Offset to plane, along the normal vector.
                                  // Distance from (0,0,0) to the plane
     long    type;                // Type of plane, depending on normal vector.
+
+    double pointDistance(const Vec3& point) const
+    {
+        return normal.dotProduct(point) - dist;
+    }
+
+    void getTangents(Vec3& tangent, Vec3& bitangent) const
+    {
+        Vec3 dir;
+        switch (type)
+        {
+        case 0:
+        case 3:
+            dir = Vec3(0.f, 1.f, 0.f);
+            break;
+        case 1:
+        case 4:
+        default:
+            dir = Vec3(0.f, 0.f, 1.f);
+            break;
+        case 2:
+        case 5:
+            dir = Vec3(1.f, 0.f, 0.f);
+            break;
+        }
+
+        tangent = normal.crossProduct(dir).normalized();
+        bitangent = tangent.crossProduct(normal);
+    }
 } plane_t;
 
 typedef struct BoundBox                 // Bounding Box, Float values
@@ -238,8 +267,7 @@ typedef struct World
             const plane_t* plane = &planes[face->plane_id];
 
             // Check if the point lies on the face's plane (it's not strictly necessary to do this, but this check makes the whole function a lot faster)
-            double pointPlaneDist = point.dotProduct(plane->normal) - plane->dist;
-            if (fabs(pointPlaneDist) > 0.001)
+            if (fabs(plane->pointDistance(point)) > 0.001)
                 continue;
 
             // Check if the point is contained within the face's polygon
diff --git a/lighting.cpp b/lighting.cpp
index 03167c4..bde36fd 100644
--- a/lighting.cpp
+++ b/lighting.cpp
@@ -373,3 +373,51 @@ unsigned char compute_faceVertex_light4(const world_t* world, const face_t* refF
 	// We should always end up with at least one sample (that from refFace itself), so if we divide by zero here something is very much wrong
 	return (unsigned char)(light / numSamples);
 }
+
+unsigned char compute_faceVertex_light5(const world_t* world, const face_t* refFace, const FaceBounds& faceBounds, Vec3 point)
+{
+	const int phaseCount = 18;
+	const float sampleRange = 16;	// Increasing this value allows lightmap samples from further away
+
+	if (refFace->lightmap < 0)
+		return 0;
+
+	auto faces = world->facesWithPoint(point);
+	if (faces.empty())
+		return 0;
+
+	const Plane* refPlane = &world->planes[refFace->plane_id];
+	Vec3 refNormal = refFace->side ? -refPlane->normal : refPlane->normal;
+
+	Vec3 tangent, bitangent;
+	refPlane->getTangents(tangent, bitangent);
+
+	Vec3 jitter;
+	unsigned int light = 0, numSamples = 0;
+	for (int index = 0; index < phaseCount; ++index)
+	{
+		getJitterOffset(&jitter.x, &jitter.y, index, phaseCount);
+		Vec3 jitteredPoint = point + (tangent * jitter.x + bitangent * jitter.y) * sampleRange;
+
+		for (auto faceIter = faces.begin(); faceIter != faces.end(); ++faceIter)
+		{
+			const face_t* face = *faceIter;
+			const plane_t* plane = &world->planes[face->plane_id];
+			vec3_t normal = face->side ? -plane->normal : plane->normal;
+
+			// Check if the face is at a shallow angle with the reference face
+			double dot = normal.dotProduct(refNormal);
+			if (dot < 0.5)
+				continue;
+
+			unsigned char sample;
+			if (!sample_lightmap(world, face, faceBounds.find(face)->second, jitteredPoint, &sample))
+				continue;
+
+			light += sample + (0xFF - face->baselight);
+			numSamples++;
+		}
+	}
+
+	return (unsigned char)(light / numSamples);
+}
diff --git a/lighting.h b/lighting.h
index 75ea3f7..b010a79 100644
--- a/lighting.h
+++ b/lighting.h
@@ -29,3 +29,4 @@ unsigned char compute_faceVertex_light2(const world_t* world, const face_t* face
 
 SurfaceList group_surfaces(const world_t* world, const VertexFaces& vertexFaces);
 unsigned char compute_faceVertex_light4(const world_t* world, const face_t* refFace, const FaceBounds& faceBounds, Vec3 point);
+unsigned char compute_faceVertex_light5(const world_t* world, const face_t* refFace, const FaceBounds& faceBounds, Vec3 point);
diff --git a/main.cpp b/main.cpp
index 68b6a4b..0176e7c 100644
--- a/main.cpp
+++ b/main.cpp
@@ -217,7 +217,7 @@ int process_faces(const world_t* world, const std::vector<ps1bsp_texture_t>& tex
 		{
 			ps1bsp_facevertex_t& faceVertex = outFaceVertices[outFace.firstFaceVertex + faceVertIdx];
 			const vertex_t* vertex = &world->vertices[faceVertex.index];
-			faceVertex.light = compute_faceVertex_light4(world, face, faceBounds, vertex->toVec());
+			faceVertex.light = compute_faceVertex_light5(world, face, faceBounds, vertex->toVec());
 			faceVertex.light = (short)((float)faceVertex.light * 1.5f);
 			if (faceVertex.light > 255)
 				faceVertex.light = 255;