Improve shadow rendering with non-default camera FOV (#11385)

* Adjust minimum filter radius for perspective

* Expand shadow frustum when camera FOV changes, reuse FOV distance adjustment from numeric.cpp

* Read shadow_soft_radius setting as float

* Use adaptive filter radius to accomodate for PSM distortion

* Adjust filter radius for texture resolution

3 files changed, 27 insertions, 17 deletions

diff --git a/src/client/shader.cpp b/src/client/shader.cpp
index 355366bd3..0b35c37af 100644
--- a/src/client/shader.cpp
+++ b/src/client/shader.cpp
@@ -740,7 +740,7 @@ ShaderInfo ShaderSource::generateShader(const std::string &name,
 		s32 shadow_filter = g_settings->getS32("shadow_filters");
 		shaders_header << "#define SHADOW_FILTER " << shadow_filter << "\n";
 
-		float shadow_soft_radius = g_settings->getS32("shadow_soft_radius");
+		float shadow_soft_radius = g_settings->getFloat("shadow_soft_radius");
 		if (shadow_soft_radius < 1.0f)
 			shadow_soft_radius = 1.0f;
 		shaders_header << "#define SOFTSHADOWRADIUS " << shadow_soft_radius << "\n";
diff --git a/src/client/shadows/dynamicshadows.cpp b/src/client/shadows/dynamicshadows.cpp
index 775cdebce..17b711a61 100644
--- a/src/client/shadows/dynamicshadows.cpp
+++ b/src/client/shadows/dynamicshadows.cpp
@@ -33,29 +33,34 @@ void DirectionalLight::createSplitMatrices(const Camera *cam)
 	v3f newCenter;
 	v3f look = cam->getDirection();
 
+	// camera view tangents
+	float tanFovY = tanf(cam->getFovY() * 0.5f);
+	float tanFovX = tanf(cam->getFovX() * 0.5f);
+
+	// adjusted frustum boundaries
+	float sfNear = shadow_frustum.zNear;
+	float sfFar = adjustDist(shadow_frustum.zFar, cam->getFovY());
+
+	// adjusted camera positions
 	v3f camPos2 = cam->getPosition();
 	v3f camPos = v3f(camPos2.X - cam->getOffset().X * BS,
 			camPos2.Y - cam->getOffset().Y * BS,
 			camPos2.Z - cam->getOffset().Z * BS);
-	camPos += look * shadow_frustum.zNear;
-	camPos2 += look * shadow_frustum.zNear;
-	float end = shadow_frustum.zNear + shadow_frustum.zFar;
-	newCenter = camPos + look * (shadow_frustum.zNear + 0.05f * end);
-	v3f world_center = camPos2 + look * (shadow_frustum.zNear + 0.05f * end);
-	// Create a vector to the frustum far corner
-	// @Liso: move all vars we can outside the loop.
-	float tanFovY = tanf(cam->getFovY() * 0.5f);
-	float tanFovX = tanf(cam->getFovX() * 0.5f);
+	camPos += look * sfNear;
+	camPos2 += look * sfNear;
 
-	const v3f &viewUp = cam->getCameraNode()->getUpVector();
-	// viewUp.normalize();
+	// center point of light frustum
+	float end = sfNear + sfFar;
+	newCenter = camPos + look * (sfNear + 0.05f * end);
+	v3f world_center = camPos2 + look * (sfNear + 0.05f * end);
 
+	// Create a vector to the frustum far corner
+	const v3f &viewUp = cam->getCameraNode()->getUpVector();
 	v3f viewRight = look.crossProduct(viewUp);
-	// viewRight.normalize();
 
 	v3f farCorner = look + viewRight * tanFovX + viewUp * tanFovY;
 	// Compute the frustumBoundingSphere radius
-	v3f boundVec = (camPos + farCorner * shadow_frustum.zFar) - newCenter;
+	v3f boundVec = (camPos + farCorner * sfFar) - newCenter;
 	radius = boundVec.getLength() * 2.0f;
 	// boundVec.getLength();
 	float vvolume = radius * 2.0f;
diff --git a/src/util/numeric.cpp b/src/util/numeric.cpp
index 99e4cfb5c..702ddce95 100644
--- a/src/util/numeric.cpp
+++ b/src/util/numeric.cpp
@@ -159,7 +159,7 @@ bool isBlockInSight(v3s16 blockpos_b, v3f camera_pos, v3f camera_dir,
 	return true;
 }
 
-s16 adjustDist(s16 dist, float zoom_fov)
+inline float adjustDist(float dist, float zoom_fov)
 {
 	// 1.775 ~= 72 * PI / 180 * 1.4, the default FOV on the client.
 	// The heuristic threshold for zooming is half of that.
@@ -167,8 +167,13 @@ s16 adjustDist(s16 dist, float zoom_fov)
 	if (zoom_fov < 0.001f || zoom_fov > threshold_fov)
 		return dist;
 
-	return std::round(dist * std::cbrt((1.0f - std::cos(threshold_fov)) /
-		(1.0f - std::cos(zoom_fov / 2.0f))));
+	return dist * std::cbrt((1.0f - std::cos(threshold_fov)) /
+		(1.0f - std::cos(zoom_fov / 2.0f)));
+}
+
+s16 adjustDist(s16 dist, float zoom_fov)
+{
+	return std::round(adjustDist((float)dist, zoom_fov));
 }
 
 void setPitchYawRollRad(core::matrix4 &m, const v3f &rot)