path: root/game/addons/zylann.hterrain/shaders/simple4_lite.gdshader

shader_type spatial;

// This is a shader with less textures, in case the main one doesn't run on your GPU.
// It's mostly a big copy/paste, because Godot doesn't support #include or #ifdef...

#include "include/heightmap.gdshaderinc"

uniform sampler2D u_terrain_heightmap;
uniform sampler2D u_terrain_normalmap;
// I had to remove `hint_albedo` from colormap in Godot 3 because it makes sRGB conversion kick in,
// which snowballs to black when doing GPU painting on that texture...
uniform sampler2D u_terrain_colormap;// : hint_albedo;
uniform sampler2D u_terrain_splatmap;
uniform mat4 u_terrain_inverse_transform;
uniform mat3 u_terrain_normal_basis;

uniform sampler2D u_ground_albedo_bump_0 : source_color;
uniform sampler2D u_ground_albedo_bump_1 : source_color;
uniform sampler2D u_ground_albedo_bump_2 : source_color;
uniform sampler2D u_ground_albedo_bump_3 : source_color;

uniform float u_ground_uv_scale = 20.0;
uniform bool u_depth_blending = true;
uniform bool u_triplanar = false;
// Each component corresponds to a ground texture. Set greater than zero to enable.
uniform vec4 u_tile_reduction = vec4(0.0, 0.0, 0.0, 0.0);

varying vec4 v_tint;
varying vec4 v_splat;
varying vec3 v_ground_uv;


vec3 unpack_normal(vec4 rgba) {
   vec3 n = rgba.xzy * 2.0 - vec3(1.0);
   // Had to negate Z because it comes from Y in the normal map,
   // and OpenGL-style normal maps are Y-up.
   n.z *= -1.0;
   return n;
}

// Blends weights according to the bump of detail textures,
// so for example it allows to have sand fill the gaps between pebbles
vec4 get_depth_blended_weights(vec4 splat, vec4 bumps) {
   float dh = 0.2;

   vec4 h = bumps + splat;
   
   // TODO Keep improving multilayer blending, there are still some edge cases...
   // Mitigation: nullify layers with near-zero splat
   h *= smoothstep(0, 0.05, splat);
   
   vec4 d = h + dh;
   d.r -= max(h.g, max(h.b, h.a));
   d.g -= max(h.r, max(h.b, h.a));
   d.b -= max(h.g, max(h.r, h.a));
   d.a -= max(h.g, max(h.b, h.r));
   
   return clamp(d, 0, 1);
}

vec3 get_triplanar_blend(vec3 world_normal) {
   vec3 blending = abs(world_normal);
   blending = normalize(max(blending, vec3(0.00001))); // Force weights to sum to 1.0
   float b = blending.x + blending.y + blending.z;
   return blending / vec3(b, b, b);
}

vec4 texture_triplanar(sampler2D tex, vec3 world_pos, vec3 blend) {
   vec4 xaxis = texture(tex, world_pos.yz);
   vec4 yaxis = texture(tex, world_pos.xz);
   vec4 zaxis = texture(tex, world_pos.xy);
   // blend the results of the 3 planar projections.
   return xaxis * blend.x + yaxis * blend.y + zaxis * blend.z;
}

vec4 depth_blend2(vec4 a, vec4 b, float t) {
   // https://www.gamasutra.com
   // /blogs/AndreyMishkinis/20130716/196339/Advanced_Terrain_Texture_Splatting.php
   float d = 0.1;
   float ma = max(a.a + (1.0 - t), b.a + t) - d;
   float ba = max(a.a + (1.0 - t) - ma, 0.0);
   float bb = max(b.a + t - ma, 0.0);
   return (a * ba + b * bb) / (ba + bb);
}

vec4 texture_antitile(sampler2D tex, vec2 uv) {
   float frequency = 2.0;
   float scale = 1.3;
   float sharpness = 0.7;
   
   // Rotate and scale UV
   float rot = 3.14 * 0.6;
   float cosa = cos(rot);
   float sina = sin(rot);
   vec2 uv2 = vec2(cosa * uv.x - sina * uv.y, sina * uv.x + cosa * uv.y) * scale;
   
   vec4 col0 = texture(tex, uv);
   vec4 col1 = texture(tex, uv2);
   //col0 = vec4(0.0, 0.0, 1.0, 1.0);
   // Periodically alternate between the two versions using a warped checker pattern
   float t = 0.5 + 0.5 
      * sin(uv2.x * frequency + sin(uv.x) * 2.0) 
      * cos(uv2.y * frequency + sin(uv.y) * 2.0);
   // Using depth blend because classic alpha blending smoothes out details
   return depth_blend2(col0, col1, smoothstep(0.5 * sharpness, 1.0 - 0.5 * sharpness, t));
}

void vertex() {
   vec2 cell_coords = (u_terrain_inverse_transform * MODEL_MATRIX * vec4(VERTEX, 1)).xz;
   // Must add a half-offset so that we sample the center of pixels,
   // otherwise bilinear filtering of the textures will give us mixed results.
   cell_coords += vec2(0.5);

   // Normalized UV
   UV = cell_coords / vec2(textureSize(u_terrain_heightmap, 0));
   
   // Height displacement
   float h = sample_heightmap(u_terrain_heightmap, UV);
   VERTEX.y = h;

   v_ground_uv = vec3(cell_coords.x, h * MODEL_MATRIX[1][1], cell_coords.y) / u_ground_uv_scale;
   
   // Putting this in vertex saves 2 fetches from the fragment shader,
   // which is good for performance at a negligible quality cost,
   // provided that geometry is a regular grid that decimates with LOD.
   // (downside is LOD will also decimate tint and splat, but it's not bad overall)
   v_tint = texture(u_terrain_colormap, UV);
   v_splat = texture(u_terrain_splatmap, UV);
   
   // Need to use u_terrain_normal_basis to handle scaling.
   NORMAL = u_terrain_normal_basis * unpack_normal(texture(u_terrain_normalmap, UV));
}

void fragment() {
   if (v_tint.a < 0.5) {
      // TODO Add option to use vertex discarding instead, using NaNs
      discard;
   }
   
   vec3 terrain_normal_world = 
      u_terrain_normal_basis * unpack_normal(texture(u_terrain_normalmap, UV));
   terrain_normal_world = normalize(terrain_normal_world);

   // TODO Detail should only be rasterized on nearby chunks (needs proximity management to switch shaders)
   
   vec2 ground_uv = v_ground_uv.xz;
   
   vec4 ab0, ab1, ab2, ab3;
   if (u_triplanar) {
      // Only do triplanar on one texture slot,
      // because otherwise it would be very expensive and cost many more ifs.
      // I chose the last slot because first slot is the default on new splatmaps,
      // and that's a feature used for cliffs, which are usually designed later.

      vec3 blending = get_triplanar_blend(terrain_normal_world);

      ab3 = texture_triplanar(u_ground_albedo_bump_3, v_ground_uv, blending);

   } else {
      if (u_tile_reduction[3] > 0.0) {
         ab3 = texture(u_ground_albedo_bump_3, ground_uv);
      } else {
         ab3 = texture_antitile(u_ground_albedo_bump_3, ground_uv);
      }
   }
   
   if (u_tile_reduction[0] > 0.0) {
      ab0 = texture_antitile(u_ground_albedo_bump_0, ground_uv);
   } else {
      ab0 = texture(u_ground_albedo_bump_0, ground_uv);
   }
   if (u_tile_reduction[1] > 0.0) {
      ab1 = texture_antitile(u_ground_albedo_bump_1, ground_uv);
   } else {
      ab1 = texture(u_ground_albedo_bump_1, ground_uv);
   }
   if (u_tile_reduction[2] > 0.0) {
      ab2 = texture_antitile(u_ground_albedo_bump_2, ground_uv);
   } else {
      ab2 = texture(u_ground_albedo_bump_2, ground_uv);
   }
   
   vec3 col0 = ab0.rgb;
   vec3 col1 = ab1.rgb;
   vec3 col2 = ab2.rgb;
   vec3 col3 = ab3.rgb;
   
   vec4 w;
   // TODO An #ifdef macro would be nice! Or copy/paste everything in a different shader...
   if (u_depth_blending) {
      w = get_depth_blended_weights(v_splat, vec4(ab0.a, ab1.a, ab2.a, ab3.a));
   } else {
      w = v_splat.rgba;
   }
   
   float w_sum = (w.r + w.g + w.b + w.a);
   
   ALBEDO = v_tint.rgb * (
      w.r * col0.rgb + 
      w.g * col1.rgb + 
      w.b * col2.rgb + 
      w.a * col3.rgb) / w_sum;
   
   ROUGHNESS = 1.0;
   
   NORMAL = (VIEW_MATRIX * (vec4(terrain_normal_world, 0.0))).xyz;

   //ALBEDO = w.rgb;
   //ALBEDO = v_ground_uv.xyz;
}