From 0abc4a258a31c62473d2235f2f5c072817a29c75 Mon Sep 17 00:00:00 2001
From: Leonardo Zide <leozide@gmail.com>
Date: Sat, 23 Feb 2019 11:33:39 -0800
Subject: [PATCH] Enabled polygon offset (with a smaller offset) for opaque
 triangles so they don't z fight with lines.

---
 common/lc_context.cpp | 36 +++++++++++++++++++++++++++++++-----
 common/lc_context.h   |  9 +++++++++
 common/lc_scene.cpp   |  2 ++
 qt/lc_qglwidget.cpp   |  3 ---
 4 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/common/lc_context.cpp b/common/lc_context.cpp
index 889fe059..1a00163a 100644
--- a/common/lc_context.cpp
+++ b/common/lc_context.cpp
@@ -35,6 +35,7 @@ lcContext::lcContext()
 	mTexture2D = 0;
 	mTexture2DMS = 0;
 	mTextureCubeMap = 0;
+	mPolygonOffset = LC_POLYGON_OFFSET_NONE;
 	mLineWidth = 1.0f;
 #ifndef LC_OPENGLES
 	mMatrixMode = GL_MODELVIEW;
@@ -241,9 +242,6 @@ void lcContext::SetDefaultState()
 	else
 		glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
-	glDisable(GL_POLYGON_OFFSET_FILL);
-	glPolygonOffset(0.5f, 0.1f);
-
 	if (gSupportsVertexBufferObject)
 	{
 		glBindBuffer(GL_ARRAY_BUFFER_ARB, 0);
@@ -294,6 +292,9 @@ void lcContext::SetDefaultState()
 	glBindTexture(GL_TEXTURE_CUBE_MAP, 0);
 	mTextureCubeMap = 0;
 
+	glDisable(GL_POLYGON_OFFSET_FILL);
+	mPolygonOffset = LC_POLYGON_OFFSET_NONE;
+
 	glLineWidth(1.0f);
 	mLineWidth = 1.0f;
 
@@ -387,6 +388,31 @@ void lcContext::SetViewport(int x, int y, int Width, int Height)
 	glViewport(x, y, Width, Height);
 }
 
+void lcContext::SetPolygonOffset(lcPolygonOffset PolygonOffset)
+{
+	if (mPolygonOffset == PolygonOffset)
+		return;
+
+	switch (PolygonOffset)
+	{
+	case LC_POLYGON_OFFSET_NONE:
+		glDisable(GL_POLYGON_OFFSET_FILL);
+		break;
+
+	case LC_POLYGON_OFFSET_OPAQUE:
+		glPolygonOffset(0.25f, 0.1f);
+		glEnable(GL_POLYGON_OFFSET_FILL);
+		break;
+
+	case LC_POLYGON_OFFSET_TRANSLUCENT:
+		glPolygonOffset(0.5f, 0.1f);
+		glEnable(GL_POLYGON_OFFSET_FILL);
+		break;
+	}
+
+	mPolygonOffset = PolygonOffset;
+}
+
 void lcContext::SetLineWidth(float LineWidth)
 {
 	if (LineWidth == mLineWidth)
@@ -408,14 +434,14 @@ void lcContext::BeginTranslucent()
 {
 	glEnable(GL_BLEND);
 	glDepthMask(GL_FALSE);
-	glEnable(GL_POLYGON_OFFSET_FILL);
+	SetPolygonOffset(LC_POLYGON_OFFSET_TRANSLUCENT);
 }
 
 void lcContext::EndTranslucent()
 {
 	glDepthMask(GL_TRUE);
 	glDisable(GL_BLEND);
-	glDisable(GL_POLYGON_OFFSET_FILL);
+	SetPolygonOffset(LC_POLYGON_OFFSET_OPAQUE);
 }
 
 void lcContext::BindTexture2D(GLuint Texture)
diff --git a/common/lc_context.h b/common/lc_context.h
index 242ddd56..64f5b227 100644
--- a/common/lc_context.h
+++ b/common/lc_context.h
@@ -100,6 +100,13 @@ public:
 	int mHeight = 0;
 };
 
+enum lcPolygonOffset
+{
+	LC_POLYGON_OFFSET_NONE,
+	LC_POLYGON_OFFSET_OPAQUE,
+	LC_POLYGON_OFFSET_TRANSLUCENT
+};
+
 class lcContext
 {
 public:
@@ -139,6 +146,7 @@ public:
 
 	void SetMaterial(lcMaterialType MaterialType);
 	void SetViewport(int x, int y, int Width, int Height);
+	void SetPolygonOffset(lcPolygonOffset PolygonOffset);
 	void SetLineWidth(float LineWidth);
 	void SetSmoothShading(bool Smooth);
 	void BeginTranslucent();
@@ -222,6 +230,7 @@ protected:
 	GLuint mTexture2D;
 	GLuint mTexture2DMS;
 	GLuint mTextureCubeMap;
+	lcPolygonOffset mPolygonOffset;
 	float mLineWidth;
 	int mMatrixMode;
 	bool mTextureEnabled;
diff --git a/common/lc_scene.cpp b/common/lc_scene.cpp
index fe9af45c..eff2d121 100644
--- a/common/lc_scene.cpp
+++ b/common/lc_scene.cpp
@@ -72,6 +72,8 @@ void lcScene::DrawRenderMeshes(lcContext* Context, int PrimitiveTypes, bool Enab
 
 	if (DrawTranslucent)
 		Context->BeginTranslucent();
+	else
+		Context->SetPolygonOffset(LC_POLYGON_OFFSET_OPAQUE);
 
 	for (int MeshIndex : Meshes)
 	{
diff --git a/qt/lc_qglwidget.cpp b/qt/lc_qglwidget.cpp
index 204a89c2..3a208aec 100644
--- a/qt/lc_qglwidget.cpp
+++ b/qt/lc_qglwidget.cpp
@@ -159,9 +159,6 @@ QSize lcQGLWidget::sizeHint() const
 
 void lcQGLWidget::initializeGL()
 {
-	glDisable(GL_POLYGON_OFFSET_FILL);
-	glPolygonOffset(0.5f, 0.1f);
-
 	glEnable(GL_DEPTH_TEST);
 	glDepthFunc(GL_LEQUAL);
 	glDepthMask(GL_TRUE);