From c38b987a01800d49d70d425d111a9962cbefcd30 Mon Sep 17 00:00:00 2001
From: IntegratedQuantum <jahe788@gmail.com>
Date: Mon, 28 Aug 2023 21:17:11 +0200
Subject: [PATCH] Fix the value range of the floating point depth buffer.

Now I can make the near plane tiny without causing any z-fighting.
---
 src/main.zig     | 2 ++
 src/renderer.zig | 7 ++++---
 src/vec.zig      | 8 ++++----
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index b3bde17f..67e6ed89 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -714,6 +714,8 @@ pub fn main() !void {
 
 	c.glCullFace(c.GL_BACK);
 	c.glEnable(c.GL_BLEND);
+	c.glClipControl(c.GL_LOWER_LEFT, c.GL_ZERO_TO_ONE);
+	c.glDepthFunc(c.GL_GREATER);
 	c.glBlendFunc(c.GL_SRC_ALPHA, c.GL_ONE_MINUS_SRC_ALPHA);
 	Window.GLFWCallbacks.framebufferSize(undefined, Window.width, Window.height);
 	var lastTime = std.time.nanoTimestamp();
diff --git a/src/renderer.zig b/src/renderer.zig
index 38eb825d..a6b2f00d 100644
--- a/src/renderer.zig
+++ b/src/renderer.zig
@@ -28,7 +28,7 @@ const Mat4f = vec.Mat4f;
 
 /// The number of milliseconds after which no more chunk meshes are created. This allows the game to run smoother on movement.
 const maximumMeshTime = 12;
-const zNear = 0.1; // TODO: Handle closer surfaces in a special function.
+const zNear = 1e-10;
 
 var fogShader: graphics.Shader = undefined;
 var fogUniforms: struct {
@@ -131,6 +131,7 @@ pub fn renderWorld(world: *World, ambientLight: Vec3f, skyColor: Vec3f, playerPo
 	_ = world;
 	worldFrameBuffer.bind();
 	gpu_performance_measuring.startQuery(.clear);
+	c.glClearDepth(0.0);
 	worldFrameBuffer.clear(Vec4f{skyColor[0], skyColor[1], skyColor[2], 1});
 	gpu_performance_measuring.stopQuery();
 	game.camera.updateViewMatrix();
@@ -203,7 +204,7 @@ pub fn renderWorld(world: *World, ambientLight: Vec3f, skyColor: Vec3f, playerPo
 	c.glUniform1f(chunk.meshing.transparentUniforms.@"waterFog.density", waterFog.density);
 
 	c.glBlendFunc(c.GL_SRC_ALPHA, c.GL_SRC1_COLOR);
-	c.glDepthFunc(c.GL_LEQUAL);
+	c.glDepthFunc(c.GL_GEQUAL);
 	c.glDepthMask(c.GL_FALSE);
 	{
 		var i: usize = meshes.len;
@@ -214,7 +215,7 @@ pub fn renderWorld(world: *World, ambientLight: Vec3f, skyColor: Vec3f, playerPo
 		}
 	}
 	c.glDepthMask(c.GL_TRUE);
-	c.glDepthFunc(c.GL_LESS);
+	c.glDepthFunc(c.GL_GREATER);
 	c.glBlendFunc(c.GL_SRC_ALPHA, c.GL_ONE_MINUS_SRC_ALPHA);
 	gpu_performance_measuring.stopQuery();
 //		NormalChunkMesh.bindTransparentShader(ambientLight, directionalLight.getDirection(), time);
diff --git a/src/vec.zig b/src/vec.zig
index 71c90809..c6cdc717 100644
--- a/src/vec.zig
+++ b/src/vec.zig
@@ -175,10 +175,10 @@ pub const Mat4f = struct {
 		const tanX = aspect*tanY;
 		return Mat4f { // Taken from https://chaosinmotion.com/2010/09/06/goodbye-far-clipping-plane/
 			.columns = [4]Vec4f { // Keep in mind that this is the transpose!
-				Vec4f{1/tanX, 0,          0,  0},
-				Vec4f{0,      1/tanY,     0,  0},
-				Vec4f{0,      0,          0, -1},
-				Vec4f{0,      0,      -near,  0},
+				Vec4f{1/tanX, 0,         0,  0},
+				Vec4f{0,      1/tanY,    0,  0},
+				Vec4f{0,      0,         0, -1},
+				Vec4f{0,      0,      near,  0},
 			}
 		};
 	}