From 680b0215fcd8781e894079ffb4140da04dffe326 Mon Sep 17 00:00:00 2001
From: vladislavbelov <vladislavbelov@wildfiregames.com>
Date: Sat, 26 Feb 2022 21:49:32 +0000
Subject: [PATCH] Adds depth bias to PipelineState and its management to
 CDeviceCommandContext.

Refs #2368

This was SVN commit r26495.
---
 source/renderer/TerrainOverlay.cpp            | 17 ++++++-----------
 source/renderer/backend/PipelineState.cpp     |  3 +++
 source/renderer/backend/PipelineState.h       |  3 +++
 .../backend/gl/DeviceCommandContext.cpp       | 19 +++++++++++++++++++
 4 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/source/renderer/TerrainOverlay.cpp b/source/renderer/TerrainOverlay.cpp
index 75d05a4bad..5bd634970e 100644
--- a/source/renderer/TerrainOverlay.cpp
+++ b/source/renderer/TerrainOverlay.cpp
@@ -124,14 +124,6 @@ void TerrainOverlay::RenderBeforeWater(
 	UNUSED2(deviceCommandContext);
 #warning TODO: implement TerrainOverlay::RenderOverlays for GLES
 #else
-	// To ensure that outlines are drawn on top of the terrain correctly (and
-	// don't Z-fight and flicker nastily), draw them as QUADS with the LINE
-	// PolygonMode, and use PolygonOffset to pull them towards the camera.
-	// (See e.g. http://www.opengl.org/resources/faq/technical/polygonoffset.htm)
-	glPolygonOffset(-1.f, -1.f);
-	//glEnable(GL_POLYGON_OFFSET_LINE);
-	glEnable(GL_POLYGON_OFFSET_FILL);
-
 	StartRender();
 
 	ssize_t min_i, min_j, max_i, max_j;
@@ -149,9 +141,6 @@ void TerrainOverlay::RenderBeforeWater(
 			ProcessTile(deviceCommandContext, m_i, m_j);
 
 	EndRender();
-
-	//glDisable(GL_POLYGON_OFFSET_LINE);
-	glDisable(GL_POLYGON_OFFSET_FILL);
 #endif
 }
 
@@ -226,6 +215,12 @@ void TerrainOverlay::RenderTile(
 		Renderer::Backend::BlendOp::ADD;
 	pipelineStateDesc.rasterizationState.cullMode =
 		drawHidden ? Renderer::Backend::CullMode::NONE : Renderer::Backend::CullMode::BACK;
+	// To ensure that outlines are drawn on top of the terrain correctly (and
+	// don't Z-fight and flicker nastily), use detph bias to pull them towards
+	// the camera.
+	pipelineStateDesc.rasterizationState.depthBiasEnabled = true;
+	pipelineStateDesc.rasterizationState.depthBiasConstantFactor = -1.0f;
+	pipelineStateDesc.rasterizationState.depthBiasSlopeFactor = -1.0f;
 	overlayTech->BeginPass();
 	deviceCommandContext->SetGraphicsPipelineState(pipelineStateDesc);
 
diff --git a/source/renderer/backend/PipelineState.cpp b/source/renderer/backend/PipelineState.cpp
index b1cc0d8411..162dc357b2 100644
--- a/source/renderer/backend/PipelineState.cpp
+++ b/source/renderer/backend/PipelineState.cpp
@@ -57,6 +57,9 @@ GraphicsPipelineStateDesc MakeDefaultGraphicsPipelineStateDesc()
 	desc.rasterizationState.polygonMode = PolygonMode::FILL;
 	desc.rasterizationState.cullMode = CullMode::BACK;
 	desc.rasterizationState.frontFace = FrontFace::COUNTER_CLOCKWISE;
+	desc.rasterizationState.depthBiasEnabled = false;
+	desc.rasterizationState.depthBiasConstantFactor = 0.0f;
+	desc.rasterizationState.depthBiasSlopeFactor = 0.0f;
 	return desc;
 }
 
diff --git a/source/renderer/backend/PipelineState.h b/source/renderer/backend/PipelineState.h
index d14dc48430..6a4e08cb1a 100644
--- a/source/renderer/backend/PipelineState.h
+++ b/source/renderer/backend/PipelineState.h
@@ -154,6 +154,9 @@ struct RasterizationStateDesc
 	PolygonMode polygonMode;
 	CullMode cullMode;
 	FrontFace frontFace;
+	bool depthBiasEnabled;
+	float depthBiasConstantFactor;
+	float depthBiasSlopeFactor;
 };
 
 // TODO: Add a shader program to the graphics pipeline state.
diff --git a/source/renderer/backend/gl/DeviceCommandContext.cpp b/source/renderer/backend/gl/DeviceCommandContext.cpp
index 1d0407ba6b..a5f4291f33 100644
--- a/source/renderer/backend/gl/DeviceCommandContext.cpp
+++ b/source/renderer/backend/gl/DeviceCommandContext.cpp
@@ -590,6 +590,25 @@ void CDeviceCommandContext::SetGraphicsPipelineStateImpl(
 			glFrontFace(GL_CCW);
 	}
 
+#if !CONFIG2_GLES
+	if (force ||
+		currentRasterizationStateDesc.depthBiasEnabled != nextRasterizationStateDesc.depthBiasEnabled)
+	{
+		if (nextRasterizationStateDesc.depthBiasEnabled)
+			glEnable(GL_POLYGON_OFFSET_FILL);
+		else
+			glDisable(GL_POLYGON_OFFSET_FILL);
+	}
+	if (force ||
+		currentRasterizationStateDesc.depthBiasConstantFactor != nextRasterizationStateDesc.depthBiasConstantFactor ||
+		currentRasterizationStateDesc.depthBiasSlopeFactor != nextRasterizationStateDesc.depthBiasSlopeFactor)
+	{
+		glPolygonOffset(
+			nextRasterizationStateDesc.depthBiasSlopeFactor,
+			nextRasterizationStateDesc.depthBiasConstantFactor);
+	}
+#endif
+
 	m_GraphicsPipelineStateDesc = pipelineStateDesc;
 }