From 29658ef3de4c99b00a279e245ebde3c43e7b84f7 Mon Sep 17 00:00:00 2001
From: Luke Benstead <kazade@gmail.com>
Date: Fri, 15 May 2020 20:43:55 +0100
Subject: [PATCH] Revert to more traditional GL depth values to fix ortho

---
 GL/draw.c                        | 14 +-------------
 samples/Makefile                 |  1 +
 samples/depth_funcs_ortho/main.c |  3 ++-
 3 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/GL/draw.c b/GL/draw.c
index 1a3f4f1..527e7dd 100644
--- a/GL/draw.c
+++ b/GL/draw.c
@@ -939,24 +939,12 @@ GL_FORCE_INLINE void divide(SubmissionTarget* target) {
     /* Perform perspective divide on each vertex */
     Vertex* vertex = _glSubmissionTargetStart(target);
 
-    /* PVR expects with invW or invZ as the final depth coordinate,
-     * but there are issues with that. Using invW means that orthographic
-     * projections fail (because W is always 1). invZ fails when stuff is near
-     * the near plane (because it ends up <= 0) so what we do is take invZ
-     * and add the near-plane distance (plus an epsilon value) to take it above 0
-     * then invert that. */
-
-    Matrix4x4* proj = _glGetProjectionMatrix();
-    float m22 = (*proj)[10];
-    float m32 = (*proj)[14];
-    float zNear = MATH_Fast_Divide((2.0f * m32), (2.0f * m22 - 2.0f));
-
     ITERATE(target->count) {
         float f = MATH_Fast_Invert(vertex->w);
         vertex->xyz[0] *= f;
         vertex->xyz[1] *= f;
         vertex->xyz[2] = MATH_Fast_Invert(
-            vertex->xyz[2] + zNear + 0.05f
+            (vertex->xyz[2] * f) * 0.5f + 0.55f
         );
         ++vertex;
     }
diff --git a/samples/Makefile b/samples/Makefile
index 49a78d8..959e9d8 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -31,3 +31,4 @@ all:
 	$(KOS_MAKE) -C mipmap all
 	$(KOS_MAKE) -C lights all
 	$(KOS_MAKE) -C depth_funcs_alpha_testing
+	$(KOS_MAKE) -C depth_funcs_ortho
diff --git a/samples/depth_funcs_ortho/main.c b/samples/depth_funcs_ortho/main.c
index 234a628..01a3639 100644
--- a/samples/depth_funcs_ortho/main.c
+++ b/samples/depth_funcs_ortho/main.c
@@ -30,7 +30,8 @@ void ReSizeGLScene(int Width, int Height)
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
 
-    //gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f);
+    glOrtho(0.0, 640.0, 0.0, 480.0, 0.0, 1.0);
+
     glMatrixMode(GL_MODELVIEW);
 }