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.

4 files changed, 48 insertions, 26 deletions

diff --git a/gfx/gl/sceneRenderer.cpp b/gfx/gl/sceneRenderer.cpp
index 5e8241f..d005dfa 100644
--- a/gfx/gl/sceneRenderer.cpp
+++ b/gfx/gl/sceneRenderer.cpp
@@ -77,6 +77,12 @@ SceneRenderer::resize(ScreenAbsCoord newSize)
 	shader.setViewPort({0, 0, size.x, size.y});
 }
 
+std::pair<const Frustum &, const Frustum &>
+SceneRenderer::preFrame(const LightDirection & lightDirection)
+{
+	return {camera, shadowMapper.preFrame(lightDirection, camera)};
+}
+
 void
 SceneRenderer::render(const SceneProvider & scene) const
 {
diff --git a/gfx/gl/sceneRenderer.h b/gfx/gl/sceneRenderer.h
index 05921a1..2ec8057 100644
--- a/gfx/gl/sceneRenderer.h
+++ b/gfx/gl/sceneRenderer.h
@@ -18,6 +18,7 @@ public:
 	void resize(ScreenAbsCoord size);
 
 	void render(const SceneProvider &) const;
+	std::pair<const Frustum &, const Frustum &> preFrame(const LightDirection &);
 	void setAmbientLight(const RGB & colour) const;
 	void setDirectionalLight(const RGB & colour, const LightDirection & direction, const SceneProvider &) const;
 
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} { }
diff --git a/gfx/gl/shadowMapper.h b/gfx/gl/shadowMapper.h
index 951e29c..82374cb 100644
--- a/gfx/gl/shadowMapper.h
+++ b/gfx/gl/shadowMapper.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "config/types.h"
+#include "gfx/frustum.h"
 #include "gfx/gl/shadowStenciller.h"
 #include "lib/glArrays.h"
 #include "program.h"
@@ -22,6 +23,7 @@ public:
 	using Definitions = std::vector<glm::mat4x4>;
 	using Sizes = std::vector<RelativePosition3D>;
 
+	const Frustum & preFrame(const LightDirection & direction, const Camera &);
 	[[nodiscard]] Definitions update(const SceneProvider &, const LightDirection & direction, const Camera &) const;
 
 	class ShadowProgram : public Program {
@@ -77,5 +79,10 @@ private:
 	glFrameBuffer depthMapFBO;
 	glTexture depthMap;
 	TextureAbsCoord size;
+
+	Definitions definitions;
+	Sizes sizes;
+	Frustum frustum;
+
 	mutable ShadowStenciller shadowStenciller;
 };