From 6b4ae04f5eee3fb9cd71156d97bdb90cf55c938e Mon Sep 17 00:00:00 2001
From: Sergey Lipskiy <gonetz@ngs.ru>
Date: Thu, 16 Mar 2017 14:56:20 +0700
Subject: [PATCH] Rewrite polygons drawing in N64 depth compare mode.

Fixed #1418: Various regressions since PR2.0 with N64 depth compare enabled
---
 .../OpenGLContext/opengl_BufferedDrawer.cpp   | 19 ++++++++++++++-----
 .../OpenGLContext/opengl_UnbufferedDrawer.cpp | 14 ++++++++++----
 src/gSP.cpp                                   |  2 --
 3 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/src/Graphics/OpenGLContext/opengl_BufferedDrawer.cpp b/src/Graphics/OpenGLContext/opengl_BufferedDrawer.cpp
index d1ca5fda..bda1e8e1 100644
--- a/src/Graphics/OpenGLContext/opengl_BufferedDrawer.cpp
+++ b/src/Graphics/OpenGLContext/opengl_BufferedDrawer.cpp
@@ -189,9 +189,6 @@ void BufferedDrawer::_updateTrianglesBuffers(const graphics::Context::DrawTriang
 
 void BufferedDrawer::drawTriangles(const graphics::Context::DrawTriangleParameters & _params)
 {
-	if (config.frameBufferEmulation.N64DepthCompare != 0)
-		glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
-
 	_updateTrianglesBuffers(_params);
 
 	if (config.generalEmulation.enableHWLighting != 0)
@@ -202,8 +199,20 @@ void BufferedDrawer::drawTriangles(const graphics::Context::DrawTriangleParamete
 		return;
 	}
 
-	glDrawElementsBaseVertex(GLenum(_params.mode), _params.elementsCount, GL_UNSIGNED_BYTE,
-		(char*)nullptr + m_trisBuffers.ebo.pos - _params.elementsCount, m_trisBuffers.vbo.pos - _params.verticesCount);
+	if (config.frameBufferEmulation.N64DepthCompare == 0) {
+		glDrawElementsBaseVertex(GLenum(_params.mode), _params.elementsCount, GL_UNSIGNED_BYTE,
+			(char*)nullptr + m_trisBuffers.ebo.pos - _params.elementsCount, m_trisBuffers.vbo.pos - _params.verticesCount);
+		return;
+	}
+
+	// Draw polygons one by one
+	const GLint eboStartPos = m_trisBuffers.ebo.pos - _params.elementsCount;
+	const GLint vboStartPos = m_trisBuffers.vbo.pos - _params.verticesCount;
+	for (GLint i = 0; i < _params.elementsCount; i += 3) {
+		glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
+		glDrawElementsBaseVertex(GLenum(_params.mode), 3, GL_UNSIGNED_BYTE,
+			(char*)nullptr + eboStartPos + i, vboStartPos);
+	}
 }
 
 void BufferedDrawer::drawLine(f32 _width, SPVertex * _vertices)
diff --git a/src/Graphics/OpenGLContext/opengl_UnbufferedDrawer.cpp b/src/Graphics/OpenGLContext/opengl_UnbufferedDrawer.cpp
index cbfe0853..5ac9c32c 100644
--- a/src/Graphics/OpenGLContext/opengl_UnbufferedDrawer.cpp
+++ b/src/Graphics/OpenGLContext/opengl_UnbufferedDrawer.cpp
@@ -38,9 +38,6 @@ bool UnbufferedDrawer::_updateAttribPointer(u32 _index, const void * _ptr)
 
 void UnbufferedDrawer::drawTriangles(const graphics::Context::DrawTriangleParameters & _params)
 {
-	if (config.frameBufferEmulation.N64DepthCompare != 0)
-		glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
-
 	{
 		m_cachedAttribArray->enableVertexAttribArray(triangleAttrib::position, true);
 		const void * ptr = &_params.vertices->x;
@@ -84,7 +81,16 @@ void UnbufferedDrawer::drawTriangles(const graphics::Context::DrawTriangleParame
 		return;
 	}
 
-	glDrawElements(GLenum(_params.mode), _params.elementsCount, GL_UNSIGNED_BYTE, _params.elements);
+	if (config.frameBufferEmulation.N64DepthCompare == 0) {
+		glDrawElements(GLenum(_params.mode), _params.elementsCount, GL_UNSIGNED_BYTE, _params.elements);
+		return;
+	}
+
+	// Draw polygons one by one
+	for (GLint i = 0; i < _params.elementsCount; i += 3) {
+		glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
+		glDrawElements(GLenum(_params.mode), 3, GL_UNSIGNED_BYTE, (u8*)_params.elements + i);
+	}
 }
 
 void UnbufferedDrawer::drawRects(const graphics::Context::DrawRectParameters & _params)
diff --git a/src/gSP.cpp b/src/gSP.cpp
index bfb00b49..25bcbfa7 100644
--- a/src/gSP.cpp
+++ b/src/gSP.cpp
@@ -60,8 +60,6 @@ void gSPTriangle(s32 v0, s32 v1, s32 v2)
 		if (drawer.isClipped(v0, v1, v2))
 			return;
 		drawer.addTriangle(v0, v1, v2);
-		if (config.frameBufferEmulation.N64DepthCompare != 0)
-			drawer.drawTriangles();
 	}
 
 	frameBufferList().setBufferChanged();