From 5273a03417b0bb1b1f9f0baabee22466c8ea440c Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Wed, 4 Mar 2026 03:12:26 +0000
Subject: Update stencils and billboards less often

No need to update these every frame when little of nothing has changed.
Instead, track the angle previously rendered and updated only when the
new angle has diverged sufficiently from this. Larger updates update
more frequently.
---
 gfx/gl/billboardPainter.cpp | 13 +++++++++----
 gfx/gl/billboardPainter.h   |  4 +++-
 gfx/gl/sceneRenderer.cpp    |  2 +-
 gfx/gl/shadowStenciller.cpp |  9 ++++++++-
 gfx/gl/shadowStenciller.h   |  2 ++
 5 files changed, 23 insertions(+), 7 deletions(-)

(limited to 'gfx')

diff --git a/gfx/gl/billboardPainter.cpp b/gfx/gl/billboardPainter.cpp
index 06e13ca..58fdce6 100644
--- a/gfx/gl/billboardPainter.cpp
+++ b/gfx/gl/billboardPainter.cpp
@@ -1,6 +1,4 @@
 #include "billboardPainter.h"
-#include "gfx/models/mesh.h"
-#include "glArrays.h"
 #include "gl_traits.h"
 #include "gldebug.h"
 #include "maths.h"
@@ -15,7 +13,7 @@ const auto VIEWS = []<GLint... Ep>(std::integer_sequence<GLint, Ep...>) {
 }(std::make_integer_sequence<GLint, BillboardPainter::VIEW_ANGLES<GLint>>());
 
 BillboardPainter::BillboardPainter() :
-	program {billboardPainter_vert, billboardPainter_geom, billboardPainter_frag}, view {}
+	program {billboardPainter_vert, billboardPainter_geom, billboardPainter_frag}, angle {}, view {}
 {
 	glDebugScope _ {fbo};
 	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
@@ -28,11 +26,18 @@ BillboardPainter::BillboardPainter() :
 }
 
 void
-BillboardPainter::setView(const glm::mat4 & newView)
+BillboardPainter::setView(const Angle newAngle, const glm::mat4 & newView)
 {
+	angle = newAngle;
 	view = newView;
 }
 
+Angle
+BillboardPainter::getAngle() const
+{
+	return angle;
+}
+
 glTextures<3>
 BillboardPainter::createBillBoardTextures(GLsizei width, GLsizei height)
 {
diff --git a/gfx/gl/billboardPainter.h b/gfx/gl/billboardPainter.h
index 4ce7b10..33c807c 100644
--- a/gfx/gl/billboardPainter.h
+++ b/gfx/gl/billboardPainter.h
@@ -15,7 +15,8 @@ public:
 
 	[[nodiscard]]
 	static glTextures<3> createBillBoardTextures(GLsizei width, GLsizei height);
-	void setView(const glm::mat4 &);
+	void setView(Angle angle, const glm::mat4 &);
+	[[nodiscard]] Angle getAngle() const;
 	void renderBillBoard(const glTextures<3> &, const MeshBase &, Texture::AnyPtr texture) const;
 
 private:
@@ -24,5 +25,6 @@ private:
 	Program::RequiredUniformLocation viewProjectionLoc {program, "viewProjection"};
 	Program::RequiredUniformLocation viewLoc {program, "view"};
 
+	Angle angle;
 	glm::mat4 view;
 };
diff --git a/gfx/gl/sceneRenderer.cpp b/gfx/gl/sceneRenderer.cpp
index efa08ef..15dde1b 100644
--- a/gfx/gl/sceneRenderer.cpp
+++ b/gfx/gl/sceneRenderer.cpp
@@ -83,7 +83,7 @@ SceneRenderer::preFrame(const SceneProvider & scene, const LightDirection lightD
 {
 	glDebugScope _ {output};
 	const auto lightView = shadowMapper.preFrame(lightDirection, camera);
-	billboardPainter.setView(camera.getView());
+	billboardPainter.setView(std::asin(camera.getForward().z), camera.getView());
 	scene.forEachRenderable([&lightView, this](Renderable * renderable) {
 		renderable->preFrame(camera, lightView);
 		renderable->updateBillboard(billboardPainter);
diff --git a/gfx/gl/shadowStenciller.cpp b/gfx/gl/shadowStenciller.cpp
index 7a0fc9b..19c8bef 100644
--- a/gfx/gl/shadowStenciller.cpp
+++ b/gfx/gl/shadowStenciller.cpp
@@ -10,7 +10,7 @@
 #include <stdexcept>
 
 ShadowStenciller::ShadowStenciller() :
-	shadowCaster {shadowStencil_vert, shadowStencil_geom, shadowStencil_frag}, viewProjections {}
+	shadowCaster {shadowStencil_vert, shadowStencil_geom, shadowStencil_frag}, lightDir {}, viewProjections {}
 {
 	glDebugScope _ {fbo};
 	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
@@ -22,6 +22,7 @@ ShadowStenciller::ShadowStenciller() :
 void
 ShadowStenciller::setLightDirection(const LightDirection & lightDir)
 {
+	this->lightDir = lightDir.position();
 	viewProjections = [&lightDir]<GLint... Ep>(std::integer_sequence<GLint, Ep...>) {
 		constexpr float STEP = two_pi / STENCIL_ANGLES<decltype(two_pi)>;
 		return std::array {rotate_pitch<4>(half_pi - lightDir.position().y)
@@ -29,6 +30,12 @@ ShadowStenciller::setLightDirection(const LightDirection & lightDir)
 	}(std::make_integer_sequence<GLint, STENCIL_ANGLES<GLint>>());
 }
 
+Direction2D
+ShadowStenciller::getLightDirection() const
+{
+	return lightDir;
+}
+
 glTexture
 ShadowStenciller::createStencilTexture(GLsizei width, GLsizei height)
 {
diff --git a/gfx/gl/shadowStenciller.h b/gfx/gl/shadowStenciller.h
index f774ac7..27ad9f9 100644
--- a/gfx/gl/shadowStenciller.h
+++ b/gfx/gl/shadowStenciller.h
@@ -16,6 +16,7 @@ public:
 	[[nodiscard]]
 	static glTexture createStencilTexture(GLsizei width, GLsizei height);
 	void setLightDirection(const LightDirection & lightDir);
+	[[nodiscard]] Direction2D getLightDirection() const;
 	void renderStencil(const glTexture &, const MeshBase &, Texture::AnyPtr texture) const;
 
 private:
@@ -23,5 +24,6 @@ private:
 	Program shadowCaster;
 	Program::RequiredUniformLocation viewProjectionLoc {shadowCaster, "viewProjection"};
 
+	Direction2D lightDir;
 	std::array<glm::mat4, STENCIL_ANGLES<size_t>> viewProjections;
 };
-- 
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