From bf2f4cb236fcf7b6d5e637f820781cc5d20b94e1 Mon Sep 17 00:00:00 2001
From: Hleb Valoshka <375gnu@gmail.com>
Date: Wed, 20 Nov 2019 20:34:54 +0300
Subject: [PATCH] Replace gluPerspective with own implementation

---
 src/celengine/render.cpp | 24 +++++++-----------------
 src/celengine/vecgl.h    | 10 ++++++++++
 src/celmath/geomutil.h   | 28 ++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 17 deletions(-)

diff --git a/src/celengine/render.cpp b/src/celengine/render.cpp
index ce04b611..49eb2caa 100644
--- a/src/celengine/render.cpp
+++ b/src/celengine/render.cpp
@@ -2479,9 +2479,7 @@ void Renderer::draw(const Observer& observer,
     pixelSize = calcPixelSize(fov, (float) windowHeight);
 
     // Set up the projection we'll use for rendering stars.
-    gluPerspective(fov,
-                   (float) windowWidth / (float) windowHeight,
-                   NEAR_DIST, FAR_DIST);
+    glMatrix(Perspective(fov, getAspectRatio(), NEAR_DIST, FAR_DIST));
 
     // Set the modelview matrix
     glMatrixMode(GL_MODELVIEW);
@@ -3337,11 +3335,9 @@ void Renderer::draw(const Observer& observer,
             // Set up a perspective projection using the current interval's near and
             // far clip planes.
             glMatrixMode(GL_PROJECTION);
-            glLoadIdentity();
-            gluPerspective(fov,
-                           (float) windowWidth / (float) windowHeight,
-                           nearPlaneDistance,
-                           farPlaneDistance);
+            glLoadMatrix(Perspective(fov, getAspectRatio(),
+                                     nearPlaneDistance,
+                                     farPlaneDistance));
             glMatrixMode(GL_MODELVIEW);
 
             Frustum intervalFrustum(degToRad(fov),
@@ -3494,10 +3490,7 @@ void Renderer::draw(const Observer& observer,
     renderForegroundAnnotations(FontNormal);
 
     glMatrixMode(GL_PROJECTION);
-    glLoadIdentity();
-    gluPerspective(fov,
-                   (float) windowWidth / (float) windowHeight,
-                   NEAR_DIST, FAR_DIST);
+    glLoadMatrix(Perspective(fov, getAspectRatio(), NEAR_DIST, FAR_DIST));
     glMatrixMode(GL_MODELVIEW);
 
     if (!selectionVisible && (renderFlags & ShowMarkers))
@@ -6747,11 +6740,8 @@ void DSORenderer::process(DeepSkyObject* const & dso,
 
                     glMatrixMode(GL_PROJECTION);
                     glPushMatrix();
-                    glLoadIdentity();
-                    gluPerspective(fov,
-                                   (float) wWidth / (float) wHeight,
-                                   nearZ,
-                                   farZ);
+                    float t = (float) wWidth / (float) wHeight;
+                    glLoadMatrix(Perspective(fov, t, nearZ, farZ));
                     glMatrixMode(GL_MODELVIEW);
                 }
 
diff --git a/src/celengine/vecgl.h b/src/celengine/vecgl.h
index 55a78755..08f75f15 100644
--- a/src/celengine/vecgl.h
+++ b/src/celengine/vecgl.h
@@ -77,6 +77,16 @@ inline void glMatrix(const Eigen::Matrix4d& m)
     glMultMatrixd(m.data());
 }
 
+inline void glLoadMatrix(const Eigen::Matrix4f& m)
+{
+    glLoadMatrixf(m.data());
+}
+
+inline void glLoadMatrix(const Eigen::Matrix4d& m)
+{
+    glLoadMatrixd(m.data());
+}
+
 inline void glScale(const Eigen::Vector3f& scale)
 {
     glScalef(scale.x(), scale.y(), scale.z());
diff --git a/src/celmath/geomutil.h b/src/celmath/geomutil.h
index 0aa51936..9ed8e720 100644
--- a/src/celmath/geomutil.h
+++ b/src/celmath/geomutil.h
@@ -87,6 +87,34 @@ Project(const Eigen::Matrix<T, 3, 1>& from,
     return true;
 }
 
+/*! Return an perspective projection matrix
+ */
+template<class T> Eigen::Matrix<T, 4, 4>
+Perspective(T fovy, T aspect, T nearZ, T farZ)
+{
+    if (aspect == T(0.0))
+        return Eigen::Matrix<T, 4, 4>::Identity();
+
+    T deltaZ = farZ - nearZ;
+    if (deltaZ == T(0.0))
+        return Eigen::Matrix<T, 4, 4>::Identity();
+
+    T angle = degToRad(fovy / 2);
+    T sine = sin(angle);
+    if (sine == T(0.0))
+        return Eigen::Matrix<T, 4, 4>::Identity();
+    T ctg = cos(angle) / sine;
+
+    Eigen::Matrix<T, 4, 4> m = Eigen::Matrix<T, 4, 4>::Identity();
+    m(0, 0) = ctg / aspect;
+    m(1, 1) = ctg;
+    m(2, 2) = -(farZ + nearZ) / deltaZ;
+    m(2, 3) = T(-2.0) * nearZ * farZ / deltaZ;
+    m(3, 2) = T(-1.0);
+    m(3, 3) = T(0.0);
+    return m;
+}
+
 }; // namespace celmath
 
 #endif // _CELMATH_GEOMUTIL_H_