From 6e7b980096e8d48da57c278c6e3c66f0e9b71a2b Mon Sep 17 00:00:00 2001
From: JackCarterSmith <jackcartersmith@jcsmith.fr>
Date: Sat, 14 Dec 2024 19:01:28 +0100
Subject: [PATCH] Experiment on simplified LoH

Another try of camera model for horizon
---
 Engine/Graphics/3DRenderer.cpp | 49 ++++++++++++++++++++++------------
 1 file changed, 32 insertions(+), 17 deletions(-)

diff --git a/Engine/Graphics/3DRenderer.cpp b/Engine/Graphics/3DRenderer.cpp
index a5f8ac6..bb687d3 100644
--- a/Engine/Graphics/3DRenderer.cpp
+++ b/Engine/Graphics/3DRenderer.cpp
@@ -31,14 +31,12 @@
 static bool VertexClipTest(M3D_F4& V, sf::Vector2f& RTsize, float gb_factor);
 
 Graphic3DRenderer::Graphic3DRenderer() {
-    mRTSize = {1280.f, 324.f};
-
     if (mMainCamera == nullptr) {
         mMainCamera = std::make_unique<Camera>();
         mMainCamera->SetPosition(0.0f, 1.5f, -8.0f);
-        mMainCamera->SetFrustrum(75.0f, mRTSize.x/mRTSize.y, 1.0f, 100.f);
-        mMainCamera->UpdateCamView();
     }
+    SetRTSize(1280.f, 324.f);
+    mMainCamera->UpdateCamView();
 
     // Fill world object list to render
     mRenderList.clear();
@@ -60,7 +58,7 @@ Graphic3DRenderer::~Graphic3DRenderer() {}
 
 void Graphic3DRenderer::SetRTSize(unsigned int w, unsigned int h) {
     mRTSize.x = w; mRTSize.y = h;
-    mMainCamera->SetFrustrum(90.0f, mRTSize.x/mRTSize.y, 1.0f, 100.f);
+    mMainCamera->SetFrustrum(75.0f, mRTSize.x/mRTSize.y, 1.0f, 100.f);
 }
 
 void Graphic3DRenderer::UpdateCamera(CAMERA_MOVE type, const float value) {
@@ -126,10 +124,10 @@ void Graphic3DRenderer::Draw(sf::RenderTexture& context) {
     const float sgRatio = ComputeSGRatio();
     sf::RectangleShape gndRect;
     if (mMainCamera->GetPos3f().y >= 0) {
-        gndRect.setSize(sf::Vector2f(1280, mRTSize.y * (1.f - sgRatio)));
-        gndRect.setPosition(sf::Vector2f(0, mRTSize.y * sgRatio));
+        gndRect.setSize(sf::Vector2f(mRTSize.x, mRTSize.y * sgRatio));
+        gndRect.setPosition(sf::Vector2f(0, mRTSize.y * (1.f - sgRatio)));
     } else {
-        gndRect.setSize(sf::Vector2f(1280, mRTSize.y * sgRatio));
+        gndRect.setSize(sf::Vector2f(mRTSize.x, mRTSize.y * (1.f - sgRatio)));
         gndRect.setPosition(sf::Vector2f(0, 0));
     }
     gndRect.setFillColor(sf::Color::Green);
@@ -233,20 +231,37 @@ void Graphic3DRenderer::UpdateInternalTestObjects() {
     mRenderList[2]->SetRotation(thetaAngle3, 0.f, thetaAngle3 * 0.5f);
     mRenderList[3]->SetRotation(0.f, thetaAngle, 0.f);
 }
-
+#include <iostream>
+// Compute the screen ratio between the ground and the sky (aka. Line of Horizon)
 inline float Graphic3DRenderer::ComputeSGRatio() {
     // FoV angle for Y axis is recovered using frustrum FoV and apply RT screen ratio to it
-    const float fovYAngle = M3D_Deg2Rad(mMainCamera->GetFoV() * (mRTSize.y/mRTSize.x));
+    //const double fovYAngleDiv2 = M3D_Deg2Rad(mMainCamera->GetFoV() * mRTSize.y / mRTSize.x) * 0.5f;
+    const double fovYAngle = M3D_Deg2Rad(mMainCamera->GetFoV()) * mRTSize.y / mRTSize.x;
     // Get the camera pitch angle over camera FoV ratio
-    float sgRatio = M3D_ScalarASinEst(mMainCamera->GetLook3f().y) / fovYAngle;
+    //const float theta = M3D_ScalarASin(-mMainCamera->GetLook3f().y) * (fovYAngleDiv2 + 0.2047198f) / M3D_PIDIV2;
+    const float theta = M3D_ScalarASin(-mMainCamera->GetLook3f().y);
+    
+    // Simple approach, real (infinite) horizon (w/o camera height and far screen calculation)
+    double sgRatio = 0.5f + std::tan(((theta / M3D_PI) / fovYAngle) * M3D_PIDIV4);
+    std::cout << (theta / M3D_PI) << ' ' << fovYAngle << ' ' << sgRatio << std::endl;
+    // Finite ground (to far plan), camera height impact the ground "level" -- KEEP FOR FURTHER USE
+    /*double sgRatio = -(mMainCamera->GetPos3f().y * 0.1f * M3D_ScalarCos(fovYAngleDiv2) - 101.f * M3D_ScalarSin(fovYAngleDiv2 + theta))
+                    / (2.f * 101.f * M3D_ScalarSin(fovYAngleDiv2) * M3D_ScalarCos(theta));
+    std::cout << fovYAngleDiv2 << ' ' << theta << ' ' << sgRatio << std::endl;*/
+    /*double p0 = 101.f / M3D_ScalarCos(fovYAngleDiv2);
+    double pf = mMainCamera->GetPos3f().y * 0.1f / M3D_ScalarSin(theta+fovYAngleDiv2);
+    double gh = (std::abs(p0 - pf) * M3D_ScalarSin(theta+fovYAngleDiv2)) / M3D_ScalarCos(theta);
+    double sh = 2.f * 101.f * std::tan(fovYAngleDiv2);
+    double sgRatio = gh / sh;
+    std::cout << fovYAngleDiv2 << ' ' << theta << " p0:" << p0 << " pf:" << pf << " gh:" << gh << " sh:" << sh << ' ' << sgRatio << std::endl;*/
 
-    // Clamp and re-scale
-    if (sgRatio > M3D_PIDIV2)  
-        sgRatio = M3D_PIDIV2;
-    else if (sgRatio < -M3D_PIDIV2)
-        sgRatio = -M3D_PIDIV2;
+    // Clamp
+    if (sgRatio > 1.f)  
+        sgRatio = 1.f;
+    else if (sgRatio < 0.f)
+        sgRatio = 0.f;
 
-    return ((sgRatio - M3D_PIDIV2) / M3D_PI) + 1.f;
+    return sgRatio;
 }
 
 inline static bool VertexClipTest(M3D_F4& V, sf::Vector2f& RTsize, float gb_factor) {