first commit

addons/zylann.hterrain/tools/brush/shaders/level.gdshader

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+shader_type canvas_item;
+render_mode blend_disabled;
+
+#include "res://addons/zylann.hterrain/shaders/include/heightmap.gdshaderinc"
+
+uniform sampler2D u_src_texture;
+uniform vec4 u_src_rect;
+uniform float u_opacity = 1.0;
+uniform float u_factor = 1.0;
+
+vec2 get_src_uv(vec2 screen_uv) {
+	vec2 uv = u_src_rect.xy + screen_uv * u_src_rect.zw;
+	return uv;
+}
+
+float get_height(sampler2D heightmap, vec2 uv) {
+	return sample_heightmap(heightmap, uv);
+}
+
+// TODO Could actually level to whatever height the brush was at the beginning of the stroke?
+
+void fragment() {
+	float brush_value = u_factor * u_opacity * texture(TEXTURE, UV).r;
+
+	// The heightmap does not have mipmaps,
+	// so we need to use an approximation of average.
+	// This is not a very good one though...
+	float dst_h = 0.0;
+	vec2 uv_min = vec2(u_src_rect.xy);
+	vec2 uv_max = vec2(u_src_rect.xy + u_src_rect.zw);
+	for (int i = 0; i < 5; ++i) {
+		for (int j = 0; j < 5; ++j) {
+			float x = mix(uv_min.x, uv_max.x, float(i) / 4.0);
+			float y = mix(uv_min.y, uv_max.y, float(j) / 4.0);
+			float h = get_height(u_src_texture, vec2(x, y));
+			dst_h += h;
+		}
+	}
+	dst_h /= (5.0 * 5.0);
+	
+	// TODO I have no idea if this will check out
+	float src_h = get_height(u_src_texture, get_src_uv(SCREEN_UV));
+	float h = mix(src_h, dst_h, brush_value);
+	COLOR = encode_height_to_viewport(h);
+}