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shader_type canvas_item;
render_mode blend_disabled;
uniform sampler2D u_src_texture;
uniform vec4 u_src_rect;
uniform float u_opacity = 1.0;
uniform int u_texture_index;
uniform int u_mode; // 0: output index, 1: output weight
uniform sampler2D u_index_map;
uniform sampler2D u_weight_map;
vec2 get_src_uv(vec2 screen_uv) {
vec2 uv = u_src_rect.xy + screen_uv * u_src_rect.zw;
return uv;
}
void fragment() {
float brush_value = u_opacity * texture(TEXTURE, UV).r;
vec2 src_uv = get_src_uv(SCREEN_UV);
vec4 iv = texture(u_index_map, src_uv);
vec4 wv = texture(u_weight_map, src_uv);
float i[3] = {iv.r, iv.g, iv.b};
float w[3] = {wv.r, wv.g, wv.b};
if (brush_value > 0.0) {
float texture_index_f = float(u_texture_index) / 255.0;
int ci = u_texture_index % 3;
float cm[3] = {-1.0, -1.0, -1.0};
cm[ci] = 1.0;
// Decompress third weight to make computations easier
w[2] = 1.0 - w[0] - w[1];
if (abs(i[ci] - texture_index_f) > 0.001) {
// Pixel does not have our texture index,
// transfer its weight to other components first
if (w[ci] > brush_value) {
w[0] -= cm[0] * brush_value;
w[1] -= cm[1] * brush_value;
w[2] -= cm[2] * brush_value;
} else if (w[ci] >= 0.f) {
w[ci] = 0.f;
i[ci] = texture_index_f;
}
} else {
// Pixel has our texture index, increase its weight
if (w[ci] + brush_value < 1.f) {
w[0] += cm[0] * brush_value;
w[1] += cm[1] * brush_value;
w[2] += cm[2] * brush_value;
} else {
// Pixel weight is full, we can set all components to the same index.
// Need to nullify other weights because they would otherwise never reach
// zero due to normalization
w[0] = 0.0;
w[1] = 0.0;
w[2] = 0.0;
w[ci] = 1.0;
i[0] = texture_index_f;
i[1] = texture_index_f;
i[2] = texture_index_f;
}
}
w[0] = clamp(w[0], 0.0, 1.0);
w[1] = clamp(w[1], 0.0, 1.0);
w[2] = clamp(w[2], 0.0, 1.0);
// Renormalize
float sum = w[0] + w[1] + w[2];
w[0] /= sum;
w[1] /= sum;
w[2] /= sum;
}
if (u_mode == 0) {
COLOR = vec4(i[0], i[1], i[2], 1.0);
} else {
COLOR = vec4(w[0], w[1], w[2], 1.0);
}
}
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