From d8464a28c6066931dd638653e2a082e2640191dc Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan.goodliffe@octal.co.uk>
Date: Wed, 18 Feb 2026 17:14:31 +0000
Subject: Fix up the preFrame process to use both frustums

(camera and directional light frustums)
This has made the whole preFrame process far more fiddly and repetitive
than I'd like, but it does work. Maybe we can tidy it up later.
---
 gfx/gl/shadowMapper.cpp | 60 ++++++++++++++++++++++++++++---------------------
 1 file changed, 34 insertions(+), 26 deletions(-)

(limited to 'gfx/gl/shadowMapper.cpp')

diff --git a/gfx/gl/shadowMapper.cpp b/gfx/gl/shadowMapper.cpp
index 7035162..a73caa0 100644
--- a/gfx/gl/shadowMapper.cpp
+++ b/gfx/gl/shadowMapper.cpp
@@ -31,7 +31,7 @@ ShadowMapper::ShadowMapper(const TextureAbsCoord & s) :
 	landmess {shadowLandmass_vert}, dynamicPointInst {shadowDynamicPointInst_vert},
 	dynamicPointInstWithTextures {shadowDynamicPointInstWithTextures_vert, shadowDynamicPointInstWithTextures_geom,
 			shadowDynamicPointInstWithTextures_frag},
-	size {s}
+	size {s}, frustum {{}, {}, {}}
 {
 	glDebugScope _ {depthMap};
 	glBindTexture(GL_TEXTURE_2D_ARRAY, depthMap);
@@ -82,6 +82,37 @@ ShadowMapper::getBandViewExtents(const Camera & camera, const glm::mat4 & lightV
 	return bandViewExtents;
 }
 
+const Frustum &
+ShadowMapper::preFrame(const LightDirection & dir, const Camera & camera)
+{
+	const auto lightViewDir = glm::lookAt({}, dir.vector(), up);
+	const auto lightViewPoint = camera.getPosition();
+	const auto bandViewExtents = getBandViewExtents(camera, lightViewDir);
+	using ExtentsBoundingBox = AxisAlignedBoundingBox<RelativeDistance>;
+	definitions.clear();
+	sizes.clear();
+	std::ranges::transform(bandViewExtents | std::views::pairwise, std::back_inserter(definitions),
+			[&lightViewDir, this](const auto & band) mutable {
+				const auto & [near, far] = band;
+				auto extents = ExtentsBoundingBox::fromPoints(std::span {near.begin(), far.end()});
+				extents.min.z -= 10'000.F;
+				extents.max.z += 10'000.F;
+				const auto lightProjection = glm::ortho(
+						extents.min.x, extents.max.x, extents.min.y, extents.max.y, -extents.max.z, -extents.min.z);
+				sizes.emplace_back(extents.max - extents.min);
+				return lightProjection * lightViewDir;
+			});
+
+	ExtentsBoundingBox extents {lightViewPoint, lightViewPoint};
+	for (const auto & point : bandViewExtents.back()) {
+		extents += point;
+	}
+	const auto lightProjection
+			= glm::ortho(extents.min.x, extents.max.x, extents.min.y, extents.max.y, -extents.max.z, -extents.min.z);
+	frustum = {lightViewPoint, lightViewDir, lightProjection};
+	return frustum;
+}
+
 ShadowMapper::Definitions
 ShadowMapper::update(const SceneProvider & scene, const LightDirection & dir, const Camera & camera) const
 {
@@ -100,39 +131,16 @@ ShadowMapper::update(const SceneProvider & scene, const LightDirection & dir, co
 	glClear(GL_DEPTH_BUFFER_BIT);
 	glViewport(0, 0, size.x, size.y);
 
-	const auto lightViewDir = glm::lookAt({}, dir.vector(), up);
 	const auto lightViewPoint = camera.getPosition();
-	const auto bandViewExtents = getBandViewExtents(camera, lightViewDir);
-	Definitions out;
-	Sizes sizes;
-	using ExtentsBoundingBox = AxisAlignedBoundingBox<RelativeDistance>;
-	std::ranges::transform(bandViewExtents | std::views::pairwise, std::back_inserter(out),
-			[&lightViewDir, &sizes](const auto & band) mutable {
-				const auto & [near, far] = band;
-				auto extents = ExtentsBoundingBox::fromPoints(std::span {near.begin(), far.end()});
-				extents.min.z -= 10'000.F;
-				extents.max.z += 10'000.F;
-				const auto lightProjection = glm::ortho(
-						extents.min.x, extents.max.x, extents.min.y, extents.max.y, -extents.max.z, -extents.min.z);
-				sizes.emplace_back(extents.max - extents.min);
-				return lightProjection * lightViewDir;
-			});
 	for (const auto p : std::initializer_list<const ShadowProgram *> {
 				 &landmess, &dynamicPoint, &dynamicPointInst, &dynamicPointInstWithTextures, &stencilShadowProgram}) {
-		p->setView(out, sizes, lightViewPoint);
-	}
-	ExtentsBoundingBox extents {lightViewPoint, lightViewPoint};
-	for (const auto & point : bandViewExtents.back()) {
-		extents += point;
+		p->setView(definitions, sizes, lightViewPoint);
 	}
-	const auto lightProjection
-			= glm::ortho(extents.min.x, extents.max.x, extents.min.y, extents.max.y, -extents.max.z, -extents.min.z);
-	Frustum frustum {lightViewPoint, lightViewDir, lightProjection};
 	scene.shadows(*this, frustum);
 
 	glCullFace(GL_BACK);
 
-	return out;
+	return definitions;
 }
 
 ShadowMapper::ShadowProgram::ShadowProgram(const Shader & vs) : Program {vs, commonShadowPoint_geom} { }
-- 
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