From 900d19a41bc1886e7a809d99d6119b12235a4f0a Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 20 Jul 2024 10:57:17 +0100
Subject: Initial commit of basic shadow depth map creation

---
 game/scenary/foliage.cpp        |  3 +++
 game/scenary/foliage.h          |  2 ++
 gfx/gl/shaders/shadowStencil.fs |  0
 gfx/gl/shaders/shadowStencil.vs | 11 +++++++++
 gfx/gl/shadowStenciller.cpp     | 51 +++++++++++++++++++++++++++++++++++++++++
 gfx/gl/shadowStenciller.h       | 21 +++++++++++++++++
 6 files changed, 88 insertions(+)
 create mode 100644 gfx/gl/shaders/shadowStencil.fs
 create mode 100644 gfx/gl/shaders/shadowStencil.vs
 create mode 100644 gfx/gl/shadowStenciller.cpp
 create mode 100644 gfx/gl/shadowStenciller.h

diff --git a/game/scenary/foliage.cpp b/game/scenary/foliage.cpp
index 73d285f..870adb0 100644
--- a/game/scenary/foliage.cpp
+++ b/game/scenary/foliage.cpp
@@ -17,6 +17,9 @@ Foliage::postLoad()
 	texture = getTexture();
 	bodyMesh->configureVAO(instanceVAO)
 			.addAttribs<LocationVertex, &LocationVertex::first, &LocationVertex::second>(instances.bufferName(), 1);
+	ShadowStenciller ss;
+	ss.renderStencil(shadowStencil, *bodyMesh, {-4000, -4000, 0}, {4000, 4000, 8000});
+	Texture::saveDepth(shadowStencil, std::format("/tmp/stencil-{}.tga", id).c_str());
 }
 
 void
diff --git a/game/scenary/foliage.h b/game/scenary/foliage.h
index 0a4261c..5367d44 100644
--- a/game/scenary/foliage.h
+++ b/game/scenary/foliage.h
@@ -2,6 +2,7 @@
 
 #include "assetFactory/asset.h"
 #include "gfx/gl/instanceVertices.h"
+#include "gfx/gl/shadowStenciller.h"
 #include "gfx/models/texture.h"
 #include "gfx/renderable.h"
 
@@ -19,6 +20,7 @@ public:
 	mutable InstanceVertices<LocationVertex> instances;
 	void render(const SceneShader &) const override;
 	void shadows(const ShadowMapper &) const override;
+	glTexture shadowStencil = ShadowStenciller::createStencilTexture(256, 256);
 
 protected:
 	friend Persistence::SelectionPtrBase<std::shared_ptr<Foliage>>;
diff --git a/gfx/gl/shaders/shadowStencil.fs b/gfx/gl/shaders/shadowStencil.fs
new file mode 100644
index 0000000..e69de29
diff --git a/gfx/gl/shaders/shadowStencil.vs b/gfx/gl/shaders/shadowStencil.vs
new file mode 100644
index 0000000..4f4c250
--- /dev/null
+++ b/gfx/gl/shaders/shadowStencil.vs
@@ -0,0 +1,11 @@
+#version 330 core
+#extension GL_ARB_shading_language_420pack : enable
+
+include(`meshIn.glsl')
+uniform mat4 viewProjection;
+
+void
+main()
+{
+	gl_Position = viewProjection * vec4(position, 1);
+}
diff --git a/gfx/gl/shadowStenciller.cpp b/gfx/gl/shadowStenciller.cpp
new file mode 100644
index 0000000..6d5fa40
--- /dev/null
+++ b/gfx/gl/shadowStenciller.cpp
@@ -0,0 +1,51 @@
+#include "shadowStenciller.h"
+#include "config/types.h"
+#include "gfx/gl/program.h"
+#include "gfx/gl/shaders/vs-shadowStencil.h"
+#include "gfx/models/mesh.h"
+#include "glArrays.h"
+#include "gl_traits.h"
+#include "maths.h"
+#include <stdexcept>
+
+ShadowStenciller::ShadowStenciller() : shadowCaster {shadowStencil_vs}
+{
+	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+	glDrawBuffer(GL_NONE);
+	glReadBuffer(GL_NONE);
+	glBindFramebuffer(GL_FRAMEBUFFER, 0);
+}
+
+glTexture
+ShadowStenciller::createStencilTexture(GLsizei width, GLsizei height)
+{
+	glTexture stencil;
+	glBindTexture(GL_TEXTURE_2D, stencil);
+	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+
+	glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+	glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, width, height, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, nullptr);
+
+	return stencil;
+}
+
+void
+ShadowStenciller::renderStencil(const glTexture & stencil, const MeshBase & mesh, const RelativePosition3D & mins,
+		const RelativePosition3D & maxs) const
+{
+	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+	glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, stencil, 0);
+	if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
+		throw std::runtime_error("Stencil framebuffer not complete!");
+	}
+	glUseProgram(shadowCaster);
+	glClear(GL_DEPTH_BUFFER_BIT);
+	glViewport(0, 0, 256, 256);
+	glEnable(GL_DEPTH_TEST);
+	const auto extents = glm::ortho(mins.x, maxs.x, mins.z, maxs.z, mins.y, maxs.y);
+	const auto lightDir = glm::lookAt({}, north, up);
+	glUniform(viewProjectionLoc, extents * lightDir);
+	mesh.Draw();
+}
diff --git a/gfx/gl/shadowStenciller.h b/gfx/gl/shadowStenciller.h
new file mode 100644
index 0000000..460fa68
--- /dev/null
+++ b/gfx/gl/shadowStenciller.h
@@ -0,0 +1,21 @@
+#pragma once
+
+#include "config/types.h"
+#include "gfx/gl/program.h"
+#include "gfx/models/mesh.h"
+#include "glArrays.h"
+
+class ShadowStenciller {
+public:
+	ShadowStenciller();
+
+	[[nodiscard]]
+	static glTexture createStencilTexture(GLsizei width, GLsizei height);
+	void renderStencil(const glTexture &, const MeshBase &, const RelativePosition3D & mins,
+			const RelativePosition3D & maxs) const;
+
+private:
+	glFrameBuffer fbo;
+	Program shadowCaster;
+	Program::UniformLocation viewProjectionLoc {shadowCaster, "viewProjection"};
+};
-- 
cgit v1.2.3