From 5ec74c35fb1f2524add7fd03ace78667f93edb2e Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 7 Sep 2024 12:35:03 +0100
Subject: Populate all layers of shadow stencil with view from all around

---
 gfx/gl/shaders/shadowStencil.gs |  6 +++---
 gfx/gl/shadowStenciller.cpp     | 18 ++++++++++++++++--
 gfx/gl/shadowStenciller.h       |  1 +
 3 files changed, 20 insertions(+), 5 deletions(-)

(limited to 'gfx')

diff --git a/gfx/gl/shaders/shadowStencil.gs b/gfx/gl/shaders/shadowStencil.gs
index eea4643..2c3f9bd 100644
--- a/gfx/gl/shaders/shadowStencil.gs
+++ b/gfx/gl/shaders/shadowStencil.gs
@@ -6,7 +6,7 @@ include(`materialDetail.glsl')
 layout(triangles) in;
 layout(triangle_strip, max_vertices = 24) out;
 
-uniform mat4 viewProjection;
+uniform mat4 viewProjection[8];
 in vec3 FragPos[];
 in vec2 TexCoords[];
 flat in MaterialDetail Material[];
@@ -16,9 +16,9 @@ flat out MaterialDetail gMaterial;
 void
 main()
 {
-	for (gl_Layer = 0; gl_Layer < 8; ++gl_Layer) {
+	for (gl_Layer = 0; gl_Layer < viewProjection.length(); ++gl_Layer) {
 		for (int v = 0; v < FragPos.length(); ++v) {
-			gl_Position = viewProjection * vec4(FragPos[v], 1);
+			gl_Position = viewProjection[gl_Layer] * vec4(FragPos[v], 1);
 			gTexCoords = TexCoords[v];
 			gMaterial = Material[v];
 			EmitVertex();
diff --git a/gfx/gl/shadowStenciller.cpp b/gfx/gl/shadowStenciller.cpp
index 1063b71..da2b3a0 100644
--- a/gfx/gl/shadowStenciller.cpp
+++ b/gfx/gl/shadowStenciller.cpp
@@ -6,9 +6,18 @@
 #include "gfx/models/mesh.h"
 #include "glArrays.h"
 #include "gl_traits.h"
+#include "maths.h"
 #include <stdexcept>
 
-ShadowStenciller::ShadowStenciller() : shadowCaster {shadowStencil_vs, shadowStencil_gs, shadowStencil_fs}
+namespace {
+	static constexpr std::array<float, 8> anglesEigthPi {-3, -2, -1, 0, 1, 2, 3, 4};
+	static const auto angles = anglesEigthPi * [](auto ep) {
+		return rotate_yaw(ep * quarter_pi);
+	};
+}
+
+ShadowStenciller::ShadowStenciller() :
+	shadowCaster {shadowStencil_vs, shadowStencil_gs, shadowStencil_fs}, viewProjections {}
 {
 	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
 	glDrawBuffer(GL_NONE);
@@ -20,6 +29,9 @@ void
 ShadowStenciller::setLightDirection(const Direction3D & lightDir, const Direction3D & lightDirUp)
 {
 	lightDirMat = glm::lookAt(-lightDir, {}, lightDirUp);
+	viewProjections = angles * [this](const auto & a) {
+		return lightDirMat * a;
+	};
 }
 
 glTexture
@@ -58,6 +70,8 @@ ShadowStenciller::renderStencil(const glTexture & stencil, const MeshBase & mesh
 	const auto & size = mesh.getDimensions().size;
 	const auto extentsMat
 			= glm::translate(glm::ortho(-size, size, -size, size, -size, size), {-centre.x, -centre.z, -centre.y});
-	glUniform(viewProjectionLoc, extentsMat * lightDirMat);
+	glUniform(viewProjectionLoc, std::span<const glm::mat4> {viewProjections * [&](const auto & vp) {
+		return extentsMat * vp;
+	}});
 	mesh.Draw();
 }
diff --git a/gfx/gl/shadowStenciller.h b/gfx/gl/shadowStenciller.h
index 925f82a..2edb955 100644
--- a/gfx/gl/shadowStenciller.h
+++ b/gfx/gl/shadowStenciller.h
@@ -20,4 +20,5 @@ private:
 	Program::RequiredUniformLocation viewProjectionLoc {shadowCaster, "viewProjection"};
 
 	glm::mat4 lightDirMat {};
+	std::array<glm::mat4, 8> viewProjections;
 };
-- 
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