diff -r cd6704009eb9 -r 3c10f0e2fbe0 src/gl/compiler.cpp
--- a/src/gl/compiler.cpp	Thu Feb 06 23:41:20 2020 +0200
+++ b/src/gl/compiler.cpp	Fri Feb 07 01:58:34 2020 +0200
@@ -31,7 +31,8 @@
 layout(location=0) in vec3 position;
 layout(location=1) in vec4 color;
 layout(location=2) in vec3 normal;
-layout(location=3) in vec3 id;
+layout(location=3) in vec3 idColor;
+layout(location=4) in int id;
 out vec4 vColor;
 out vec3 vFragPos;
 out vec3 vNormal;
@@ -39,6 +40,8 @@
 uniform mat4 viewMatrix;
 uniform mat4 projectionMatrix;
 uniform int fragmentStyle;
+uniform vec3 selectedColor;
+uniform int highlighted;
 
 const int FRAGSTYLE_Normal = 0;
 const int FRAGSTYLE_BfcGreen = 1;
@@ -50,22 +53,30 @@
 {
 	mat3 normalMatrix = transpose(inverse(mat3(modelMatrix)));
 	vNormal = normalize(normalMatrix * normal);
-	if (fragmentStyle == FRAGSTYLE_BfcGreen)
-	{
-		vColor = vec4(0.2, 0.9, 0.2, 1.0);
-	}
-	else if (fragmentStyle == FRAGSTYLE_BfcRed)
+	if (fragmentStyle == FRAGSTYLE_Id)
 	{
-		vColor = vec4(0.9, 0.2, 0.2, 1.0);
-	}
-	else if (fragmentStyle == FRAGSTYLE_Id)
-	{
-		vColor = vec4(id, 1.0);
+		vColor = vec4(idColor, 1.0);
 	}
 	else
 	{
-		vColor = color;
+		if (fragmentStyle == FRAGSTYLE_BfcGreen)
+		{
+			vColor = vec4(0.2, 0.9, 0.2, 1.0);
+		}
+		else if (fragmentStyle == FRAGSTYLE_BfcRed)
+		{
+			vColor = vec4(0.9, 0.2, 0.2, 1.0);
+		}
+		else
+		{
+			vColor = color;
+		}
+		if (highlighted == id)
+		{
+			vColor = (vColor + vec4(selectedColor, 1.0) * 0.6) / 1.6;
+		}
 	}
+
 	vFragPos = vec3(modelMatrix * vec4(position, 1.0));
 	gl_Position = projectionMatrix * viewMatrix * vec4(vFragPos, 1.0);
 }
@@ -142,15 +153,16 @@
 			object.buffer.setUsagePattern(QOpenGLBuffer::DynamicDraw);
 			object.vertexArray.create();
 			object.vertexArray.bind();
-			object.program->enableAttributeArray(0);
-			object.program->enableAttributeArray(1);
-			object.program->enableAttributeArray(2);
-			object.program->enableAttributeArray(3);
+			for (int k : {0, 1, 2, 3, 4})
+			{
+				object.program->enableAttributeArray(k);
+			}
 			constexpr int stride = sizeof(gl::Vertex);
 			object.program->setAttributeBuffer(0, GL_FLOAT, offsetof(gl::Vertex, position), 3, stride);
 			object.program->setAttributeBuffer(1, GL_FLOAT, offsetof(gl::Vertex, color), 4, stride);
 			object.program->setAttributeBuffer(2, GL_FLOAT, offsetof(gl::Vertex, normal), 3, stride);
-			object.program->setAttributeBuffer(3, GL_FLOAT, offsetof(gl::Vertex, id), 3, stride);
+			object.program->setAttributeBuffer(3, GL_FLOAT, offsetof(gl::Vertex, idColor), 3, stride);
+			glVertexAttribIPointer(4, 1, GL_INT, stride, (void*)offsetof(gl::Vertex, id));
 			object.vertexArray.release();
 			object.buffer.release();
 			object.program->release();
@@ -230,7 +242,8 @@
 		vertex.position = polygon.vertices[i];
 		vertex.normal = glm::normalize(glm::cross(v1 - v2, v3 - v2));
 		vertex.color = glm::vec4{color.redF(), color.greenF(), color.blueF(), color.alphaF()};
-		vertex.id = colorFromId(polygon.id);
+		vertex.idColor = colorFromId(polygon.id);
+		vertex.id = polygon.id.value;
 	}
 }