game/addons/zylann.hterrain/tools/brush/shaders/alpha.gdshader


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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 float u_value = 1.0;

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;
   
   vec4 src = texture(u_src_texture, get_src_uv(SCREEN_UV));
   COLOR = vec4(src.rgb, mix(src.a, u_value, brush_value));
}