173 lines
5.7 KiB
Text
173 lines
5.7 KiB
Text
shader_type spatial;
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// This shader uses a texture array with multiple splatmaps, allowing up to 16 textures.
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// Only the 4 textures having highest blending weight are sampled.
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// I had to remove source_color` from colormap in Godot 3 because it makes sRGB conversion kick in,
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// which snowballs to black when doing GPU painting on that texture...
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uniform sampler2D u_terrain_colormap;
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uniform sampler2D u_terrain_splatmap;
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uniform sampler2D u_terrain_splatmap_1;
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uniform sampler2D u_terrain_splatmap_2;
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uniform sampler2D u_terrain_splatmap_3;
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uniform sampler2DArray u_ground_albedo_bump_array : source_color;
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uniform float u_ground_uv_scale = 20.0;
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uniform bool u_depth_blending = true;
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// TODO Can't put this in a constant: https://github.com/godotengine/godot/issues/44145
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//const int TEXTURE_COUNT = 16;
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// Blends weights according to the bump of detail textures,
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// so for example it allows to have sand fill the gaps between pebbles
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vec4 get_depth_blended_weights(vec4 splat, vec4 bumps) {
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float dh = 0.2;
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vec4 h = bumps + splat;
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// TODO Keep improving multilayer blending, there are still some edge cases...
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// Mitigation: nullify layers with near-zero splat
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h *= smoothstep(0, 0.05, splat);
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vec4 d = h + dh;
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d.r -= max(h.g, max(h.b, h.a));
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d.g -= max(h.r, max(h.b, h.a));
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d.b -= max(h.g, max(h.r, h.a));
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d.a -= max(h.g, max(h.b, h.r));
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return clamp(d, 0, 1);
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}
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void get_splat_weights(vec2 uv, out vec4 out_high_indices, out vec4 out_high_weights) {
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vec4 ew0 = texture(u_terrain_splatmap, uv);
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vec4 ew1 = texture(u_terrain_splatmap_1, uv);
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vec4 ew2 = texture(u_terrain_splatmap_2, uv);
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vec4 ew3 = texture(u_terrain_splatmap_3, uv);
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float weights[16] = {
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ew0.r, ew0.g, ew0.b, ew0.a,
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ew1.r, ew1.g, ew1.b, ew1.a,
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ew2.r, ew2.g, ew2.b, ew2.a,
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ew3.r, ew3.g, ew3.b, ew3.a
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};
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// float weights_sum = 0.0;
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// for (int i = 0; i < 16; ++i) {
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// weights_sum += weights[i];
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// }
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// for (int i = 0; i < 16; ++i) {
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// weights_sum /= weights_sum;
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// }
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// weights_sum=1.1;
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// Now we have to pick the 4 highest weights and use them to blend textures.
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// Using arrays because Godot's shader version doesn't support dynamic indexing of vectors
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// TODO We should not need to initialize, but apparently we don't always find 4 weights
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int high_indices_array[4] = {0, 0, 0, 0};
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float high_weights_array[4] = {0.0, 0.0, 0.0, 0.0};
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int count = 0;
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// We know weights are supposed to be normalized.
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// That means the highest value of the pivot above which we can find 4 results
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// is 1.0 / 4.0. However that would mean exactly 4 textures have exactly that weight,
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// which is very unlikely. If we consider 1.0 / 5.0, we are a bit more likely to find
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// 4 results, and finding 5 results remains almost impossible.
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float pivot = /*weights_sum*/1.0 / 5.0;
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for (int i = 0; i < 16; ++i) {
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if (weights[i] > pivot) {
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high_weights_array[count] = weights[i];
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high_indices_array[count] = i;
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weights[i] = 0.0;
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++count;
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}
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}
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while (count < 4 && pivot > 0.0) {
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float max_weight = 0.0;
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int max_index = 0;
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for (int i = 0; i < 16; ++i) {
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if (/*weights[i] <= pivot && */weights[i] > max_weight) {
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max_weight = weights[i];
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max_index = i;
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weights[i] = 0.0;
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}
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}
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high_indices_array[count] = max_index;
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high_weights_array[count] = max_weight;
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++count;
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pivot = max_weight;
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}
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out_high_weights = vec4(
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high_weights_array[0], high_weights_array[1],
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high_weights_array[2], high_weights_array[3]);
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out_high_indices = vec4(
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float(high_indices_array[0]), float(high_indices_array[1]),
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float(high_indices_array[2]), float(high_indices_array[3]));
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out_high_weights /=
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out_high_weights.r + out_high_weights.g + out_high_weights.b + out_high_weights.a;
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}
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void vertex() {
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vec4 wpos = MODEL_MATRIX * vec4(VERTEX, 1);
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vec2 cell_coords = wpos.xz;
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// Must add a half-offset so that we sample the center of pixels,
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// otherwise bilinear filtering of the textures will give us mixed results (#183)
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cell_coords += vec2(0.5);
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// Normalized UV
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UV = cell_coords / vec2(textureSize(u_terrain_splatmap, 0));
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}
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void fragment() {
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// These were moved from vertex to fragment,
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// so we can generate part of the global map with just one quad and we get full quality
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vec3 tint = texture(u_terrain_colormap, UV).rgb;
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vec4 splat = texture(u_terrain_splatmap, UV);
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vec4 high_indices;
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vec4 high_weights;
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get_splat_weights(UV, high_indices, high_weights);
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// Get bump at normal resolution so depth blending is accurate
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vec2 ground_uv = UV / u_ground_uv_scale;
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float b0 = texture(u_ground_albedo_bump_array, vec3(ground_uv, high_indices.x)).a;
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float b1 = texture(u_ground_albedo_bump_array, vec3(ground_uv, high_indices.y)).a;
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float b2 = texture(u_ground_albedo_bump_array, vec3(ground_uv, high_indices.z)).a;
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float b3 = texture(u_ground_albedo_bump_array, vec3(ground_uv, high_indices.w)).a;
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// Take the center of the highest mip as color, because we can't see details from far away.
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vec2 ndc_center = vec2(0.5, 0.5);
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vec3 a0 = textureLod(u_ground_albedo_bump_array, vec3(ndc_center, high_indices.x), 10.0).rgb;
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vec3 a1 = textureLod(u_ground_albedo_bump_array, vec3(ndc_center, high_indices.y), 10.0).rgb;
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vec3 a2 = textureLod(u_ground_albedo_bump_array, vec3(ndc_center, high_indices.z), 10.0).rgb;
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vec3 a3 = textureLod(u_ground_albedo_bump_array, vec3(ndc_center, high_indices.w), 10.0).rgb;
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vec3 col0 = a0 * tint;
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vec3 col1 = a1 * tint;
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vec3 col2 = a2 * tint;
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vec3 col3 = a3 * tint;
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vec4 w;
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// TODO An #ifdef macro would be nice! Or copy/paste everything in a different shader...
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if (u_depth_blending) {
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w = get_depth_blended_weights(high_weights, vec4(b0, b1, b2, b3));
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} else {
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w = high_weights;
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}
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float w_sum = (w.r + w.g + w.b + w.a);
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ALBEDO = (
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w.r * col0.rgb +
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w.g * col1.rgb +
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w.b * col2.rgb +
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w.a * col3.rgb) / w_sum;
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}
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