godot/doc/classes/CanvasGroup.xml

<?xml version="1.0" encoding="UTF-8" ?>
<class name="CanvasGroup" inherits="Node2D" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
	<brief_description>
		Merges several 2D nodes into a single draw operation.
	</brief_description>
	<description>
		Child [CanvasItem] nodes of a [CanvasGroup] are drawn as a single object. It allows to e.g. draw overlapping translucent 2D nodes without blending (set [member CanvasItem.self_modulate] property of [CanvasGroup] to achieve this effect).
		[b]Note:[/b] The [CanvasGroup] uses a custom shader to read from the backbuffer to draw its children. Assigning a [Material] to the [CanvasGroup] overrides the builtin shader. To duplicate the behavior of the builtin shader in a custom [Shader] use the following:
		[codeblock]
		shader_type canvas_item;
		render_mode unshaded;

		uniform sampler2D screen_texture : hint_screen_texture, repeat_disable, filter_nearest;

		void fragment() {
		    vec4 c = textureLod(screen_texture, SCREEN_UV, 0.0);

		    if (c.a &gt; 0.0001) {
		        c.rgb /= c.a;
		    }

		    COLOR *= c;
		}
		[/codeblock]
		[b]Note:[/b] Since [CanvasGroup] and [member CanvasItem.clip_children] both utilize the backbuffer, children of a [CanvasGroup] who have their [member CanvasItem.clip_children] set to anything other than [constant CanvasItem.CLIP_CHILDREN_DISABLED] will not function correctly.
	</description>
	<tutorials>
	</tutorials>
	<members>
		<member name="clear_margin" type="float" setter="set_clear_margin" getter="get_clear_margin" default="10.0">
			Sets the size of the margin used to expand the clearing rect of this [CanvasGroup]. This expands the area of the backbuffer that will be used by the [CanvasGroup]. A smaller margin will reduce the area of the backbuffer used which can increase performance, however if [member use_mipmaps] is enabled, a small margin may result in mipmap errors at the edge of the [CanvasGroup]. Accordingly, this should be left as small as possible, but should be increased if artifacts appear along the edges of the canvas group.
		</member>
		<member name="fit_margin" type="float" setter="set_fit_margin" getter="get_fit_margin" default="10.0">
			Sets the size of a margin used to expand the drawable rect of this [CanvasGroup]. The size of the [CanvasGroup] is determined by fitting a rect around its children then expanding that rect by [member fit_margin]. This increases both the backbuffer area used and the area covered by the [CanvasGroup] both of which can reduce performance. This should be kept as small as possible and should only be expanded when an increased size is needed (e.g. for custom shader effects).
		</member>
		<member name="use_mipmaps" type="bool" setter="set_use_mipmaps" getter="is_using_mipmaps" default="false">
			If [code]true[/code], calculates mipmaps for the backbuffer before drawing the [CanvasGroup] so that mipmaps can be used in a custom [ShaderMaterial] attached to the [CanvasGroup]. Generating mipmaps has a performance cost so this should not be enabled unless required.
		</member>
	</members>
</class>