feat(editor): vertical profile editor, grade lines kept in the scenery

application/editorprojection.h

@@ -0,0 +1,63 @@
+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#pragma once
+
+#include "application/editormode.h"
+#include "rendering/renderer.h"
+#include "imgui/imgui.h"
+
+// world to screen projection of the current camera, for overlays drawn with ImGui
+class screen_projection
+{
+  public:
+	screen_projection()
+	{
+		ImGuiIO const &io = ImGui::GetIO();
+		m_size = io.DisplaySize;
+		m_camera = GfxRenderer->Camera_Position();
+		float const aspect = m_size.y > 0.0f ? m_size.x / m_size.y : 1.0f;
+		m_viewprojection = editor_mode::projection_matrix(aspect) * GfxRenderer->Camera_View_Matrix();
+	}
+
+	glm::vec4 clip(glm::dvec3 const &Point) const
+	{
+		return m_viewprojection * glm::vec4(glm::vec3(Point - m_camera), 1.0f);
+	}
+	ImVec2 screen(glm::vec4 const &Clip) const
+	{
+		return ImVec2((Clip.x / Clip.w * 0.5f + 0.5f) * m_size.x, (0.5f - Clip.y / Clip.w * 0.5f) * m_size.y);
+	}
+	bool project(glm::dvec3 const &Point, ImVec2 &Screen) const
+	{
+		auto const c = clip(Point);
+		if (c.w < kNear)
+			return false;
+		Screen = screen(c);
+		return true;
+	}
+	void line(ImDrawList *Drawlist, glm::dvec3 const &A, glm::dvec3 const &B, ImU32 const Color, float const Thickness) const
+	{
+		glm::vec4 a = clip(A);
+		glm::vec4 b = clip(B);
+		if (a.w < kNear && b.w < kNear)
+			return;
+		if (a.w < kNear)
+			a = glm::mix(a, b, (kNear - a.w) / (b.w - a.w));
+		else if (b.w < kNear)
+			b = glm::mix(b, a, (kNear - b.w) / (a.w - b.w));
+		Drawlist->AddLine(screen(a), screen(b), Color, Thickness);
+	}
+
+  private:
+	static constexpr float kNear{0.1f};
+	ImVec2 m_size;
+	glm::dvec3 m_camera;
+	glm::mat4 m_viewprojection;
+};