diff -r eee644f88e93 -r 3af627f7a40f src/gl/partrenderer.cpp
--- a/src/gl/partrenderer.cpp	Sat Feb 08 00:08:57 2020 +0200
+++ b/src/gl/partrenderer.cpp	Thu Feb 13 12:51:27 2020 +0200
@@ -33,7 +33,8 @@
 	model{model},
 	documents{documents},
 	colorTable{colorTable},
-	compiler{new gl::Compiler{this->colorTable, this}}
+	compiler{new gl::Compiler{this->colorTable, this}},
+	gridProgram{this}
 {
 	this->setMouseTracking(true);
 }
@@ -42,6 +43,11 @@
 {
 }
 
+static QVector3D vec3FromQColor(const QColor& color)
+{
+	return {(float)color.redF(), (float)color.greenF(), (float)color.blueF()};
+}
+
 void PartRenderer::initializeGL()
 {
 	this->initializeOpenGLFunctions();
@@ -49,6 +55,8 @@
 	{
 		abort();
 	}
+	this->gridProgram.emplace(this);
+	this->gridProgram->initialize();
 	this->compiler->initialize();
 	this->compiler->build(this->model, this->documents, this->renderPreferences);
 	this->initialized = true;
@@ -67,6 +75,7 @@
 		0.1f,
 		10000.f);
 	this->compiler->setUniformMatrix("projectionMatrix", this->projectionMatrix);
+	this->gridProgram->setProjectionMatrix(this->projectionMatrix);
 }
 
 static GLenum getGlTypeForArrayClass(const gl::ArrayClass vboClass)
@@ -88,17 +97,12 @@
 {
 	glEnable(GL_DEPTH_TEST);
 	glShadeModel(GL_SMOOTH);
-	glEnable(GL_MULTISAMPLE);
 	this->renderScene();
 }
 
-static QVector3D vec3FromQColor(const QColor& color)
-{
-	return {(float)color.redF(), (float)color.greenF(), (float)color.blueF()};
-}
-
 void PartRenderer::renderScene()
 {
+	this->checkForGLErrors();
 	if (this->renderPreferences.lineAntiAliasing && this->renderPreferences.style != gl::RenderStyle::PickScene)
 	{
 		glEnable(GL_LINE_SMOOTH);
@@ -122,6 +126,7 @@
 		glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
 		this->compiler->setUniform("useLighting", GL_FALSE);
 	}
+	this->checkForGLErrors();
 	this->compiler->setUniform("selectedColor", vec3FromQColor(this->renderPreferences.selectedColor));
 	this->compiler->setUniform("highlighted", this->highlighted.value);
 	this->checkForGLErrors();
@@ -164,6 +169,10 @@
 		this->renderAllArrays();
 		break;
 	}
+	glEnable(GL_BLEND);
+	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+	this->gridProgram->draw();
+	glDisable(GL_BLEND);
 	glDisable(GL_POLYGON_OFFSET_FILL);
 }
 
@@ -182,6 +191,7 @@
 	const double z  = 2 * std::exp(this->zoom) * (1 + this->compiler->modelDistance());
 	this->viewMatrix = glm::lookAt(glm::vec3{0, 0, z}, {0, 0, 0}, {0, -1, 0});
 	this->compiler->setUniformMatrix("viewMatrix", this->viewMatrix);
+	this->gridProgram->setViewMatrix(this->viewMatrix);
 }
 
 void PartRenderer::renderVao(const gl::ArrayClass arrayClass)
@@ -197,6 +207,11 @@
 
 void PartRenderer::checkForGLErrors()
 {
+	gl::checkForGLErrors(this);
+}
+
+void gl::checkForGLErrors(QWidget* parent)
+{
 	GLenum glError;
 	QStringList errors;
 	while ((glError = glGetError()) != GL_NO_ERROR)
@@ -206,12 +221,12 @@
 	}
 	if (not errors.isEmpty())
 	{
-		QMessageBox box{this};
+		QMessageBox box{parent};
 		box.setIcon(QMessageBox::Critical);
-		box.setText(tr("Failed to render: %1").arg(errors.join("\n")));
-		box.setWindowTitle(tr("Rendering error"));
+		box.setText(QObject::tr("OpenGL error: %1").arg(errors.join("\n")));
+		box.setWindowTitle(QObject::tr("OpenGL error"));
 		box.setStandardButtons(QMessageBox::Close);
-		box.button(QMessageBox::Close)->setText(tr("Damn it"));
+		box.button(QMessageBox::Close)->setText(QObject::tr("Damn it"));
 		box.exec();
 	}
 }
@@ -231,7 +246,9 @@
 		const glm::quat q_x = glm::angleAxis(scalar * move_x, glm::vec3{0, -1, 0});
 		const glm::quat q_y = glm::angleAxis(scalar * move_y, glm::vec3{-1, 0, 0});
 		this->modelQuaternion = q_x * q_y * this->modelQuaternion;
-		this->compiler->setUniformMatrix("modelMatrix", glm::mat4_cast(this->modelQuaternion));
+		const glm::mat4 modelMatrix = glm::mat4_cast(this->modelQuaternion);
+		this->compiler->setUniformMatrix("modelMatrix", modelMatrix);
+		this->gridProgram->setModelMatrix(modelMatrix);
 		this->update();
 	}
 	this->lastMousePosition = pointToPointF(event->pos());