From 48a4ada4f9aa1f6b02e7cab1f5819eaf287dbbbd Mon Sep 17 00:00:00 2001
From: Mikulas Florek <mikulas.florek@gamedev.sk>
Date: Fri, 20 Oct 2023 14:41:54 +0200
Subject: [PATCH] grid from
 https://bgolus.medium.com/the-best-darn-grid-shader-yet-727f9278b9d8

---
 data/pipelines/grid.shd | 52 +++++++++++++++++++++++++++++++++++++++++
 data/pipelines/main.lua | 11 +++++++++
 2 files changed, 63 insertions(+)
 create mode 100644 data/pipelines/grid.shd

diff --git a/data/pipelines/grid.shd b/data/pipelines/grid.shd
new file mode 100644
index 0000000000..40f5ad893c
--- /dev/null
+++ b/data/pipelines/grid.shd
@@ -0,0 +1,52 @@
+include "pipelines/common.glsl"
+
+------------------
+
+vertex_shader [[
+	layout(std140, binding = 4) uniform Model {
+		mat4 u_model;
+	};
+	
+	out vec4 v_lpos; 
+
+	void main() {
+		vec3 local_pos = vec3(gl_VertexID & 1, 0, gl_VertexID >> 1) * 1000 - 500;
+		local_pos.y = 0;
+		v_lpos = vec4(local_pos, 1);
+		vec4 p = vec4(local_pos - Global.camera_world_pos.xyz,  1);
+		gl_Position = Global.projection_no_jitter * Global.view * p;
+	}
+]]
+
+---------------------
+
+fragment_shader [[
+	layout(location = 0) out vec4 o_color;
+
+	 // https://bgolus.medium.com/the-best-darn-grid-shader-yet-727f9278b9d8
+	 // https://gist.github.com/bgolus/d49651f52b1dcf82f70421ba922ed064
+	 float PristineGrid(vec2 uv, vec2 lineWidth) {
+        vec4 uvDDXY = vec4(dFdx(uv), dFdy(uv));
+        vec2 uvDeriv = vec2(length(uvDDXY.xz), length(uvDDXY.yw));
+        bvec2 invertLine = lessThan(lineWidth, vec2(0.5));
+        vec2 targetWidth = mix(1.0 - lineWidth, lineWidth, invertLine);
+        vec2 drawWidth = clamp(targetWidth, uvDeriv, vec2(0.5));
+        vec2 lineAA = uvDeriv * 1.5;
+        vec2 gridUV = abs(fract(uv) * 2.0 - 1.0);
+        gridUV = mix(gridUV, 1.0 - gridUV, invertLine);
+        vec2 grid2 = smoothstep(drawWidth + lineAA, drawWidth - lineAA, gridUV);
+        grid2 *= saturate(targetWidth / drawWidth);
+        grid2 = mix(grid2, targetWidth, saturate(uvDeriv * 2.0 - 1.0));
+        grid2 = mix(1.0 - grid2, grid2, invertLine);
+        return mix(grid2.x, 1.0, grid2.y);
+    }
+
+	in vec4 v_lpos;
+
+	void main() {
+		vec2 uv = v_lpos.xz / v_lpos.w;
+		float grid = PristineGrid(uv, vec2(0.005));
+		if (grid < 0.0) discard;
+		o_color = vec4(vec3(0.0), grid);
+	}
+]]
\ No newline at end of file
diff --git a/data/pipelines/main.lua b/data/pipelines/main.lua
index b4dbd475d2..23fa170dd5 100644
--- a/data/pipelines/main.lua
+++ b/data/pipelines/main.lua
@@ -7,6 +7,7 @@ local cubemap_sky = require "pipelines/cubemap_sky"
 local film_grain =  require "pipelines/film_grain"
 local fxaa =  require "pipelines/fxaa"
 
+local grid_shader = preloadShader("pipelines/grid.shd")
 local lighting_shader = preloadShader("pipelines/lighting.shd")
 local field_debug_shader = preloadShader("pipelines/field_debug.shd")
 textured_quad_shader = preloadShader("pipelines/textured_quad.shd")
@@ -31,6 +32,7 @@ local taa_history = -1
 local render_grass = true
 local render_impostors = true
 local render_terrain = true
+local enable_grid = true
 
 type GBuffer = {
 	A : RenderBuffer,
@@ -319,6 +321,12 @@ blur = function(buffer: RenderBuffer, w : number, h : number, rb_desc : RenderBu
 	setRenderTargets()
 end
 
+local function grid()
+	if enable_grid then
+		drawArray(0, 4, grid_shader, {}, transparent_state);
+	end
+end
+
 local function shadowPass() : RenderBuffer
 	if not environmentCastShadows() then
 		local rb = createRenderbuffer(shadowmap_1x1)
@@ -572,6 +580,8 @@ main = function()
 	if SCENE_VIEW ~= nil then
 		local icon_ds = createRenderbuffer(icon_ds_desc)
 		pass(view_params)
+			setRenderTargetsDS(res, gbuffer.DS)
+			grid()
 			setRenderTargetsDS(res, icon_ds)
 			clear(CLEAR_DEPTH, 0, 0, 0, 1, 0)
 			renderGizmos()
@@ -659,6 +669,7 @@ onGUI = function()
 		_, render_impostors = ImGui.Checkbox("Impostors", render_impostors)
 		_, render_terrain = ImGui.Checkbox("Terrain", render_terrain)
 		_, enable_icons = ImGui.Checkbox("Icons", enable_icons)
+		_, enable_grid = ImGui.Checkbox("Grid", enable_grid)
 		local changed, upsample = ImGui.DragFloat("Downsample", getRenderToDisplayRatio())
 		if changed then
 			if upsample < 1 then upsample = 1 end