Differential D27984 Diff 77446 src/scenegraph/shadowedrectangle.frag

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src/scenegraph/shadowedrectangle.frag

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		1		/*
		2		* SPDX-FileCopyrightText: 2020 Arjen Hiemstra <ahiemstra@heimr.nl>
		3		*
		4		* SPDX-License-Identifier: LGPL-2.0-or-later
		5		*/
		6
		7		// This is based on the 2D SDF functions provided by Inigo Quilez:
		8		// https://iquilezles.org/www/articles/distfunctions2d/distfunctions2d.htm
		9
		10		uniform lowp float opacity;
		11		uniform lowp float size;
		12		uniform lowp float radius;
		13		uniform lowp vec4 color;
		14		uniform lowp vec4 shadowColor;
		15		uniform lowp vec2 offset;
		16		uniform lowp vec2 aspect;
		17
		18		varying lowp vec2 uv;
		19
		20		const lowp float minimum_shadow_radius = 0.05;
		21
		22		// Calculate the distance to a rectangle with rounded corners.
		23		// \param point The point to calculate the distance of.
		24		// \param rect The rectangle to calculate the distance of.
		25		// \param translation The amount of translation to apply to the rectangle.
		26		// \param radius A vec4 with the radius of each corner.
		27		lowp float sdf_rounded_rectangle(in lowp vec2 point, in lowp vec2 rect, in lowp vec2 translation, in lowp vec4 radius)
		28		{
		29		radius.xy = (point.x > 0.0) ? radius.xy : radius.zw;
		30		radius.x = (point.y > 0.0) ? radius.x : radius.y;
		31		lowp vec2 d = abs(point - translation) - rect + radius.x;
		32		return min(max(d.x, d.y), 0.0) + length(max(d, 0.0)) - radius.x;
		33		}
		34
		35		void main()
		36		{
		37		// Scaling factor that is the inverse of the amount of scaling applied to the geometry.
		38		lowp float inverse_scale = 1.0 / (1.0 + size + length(offset) * 2.0);
		39
		40		// Correction factor to round the corners of a larger shadow.
		41		// We want to account for size in regards to shadow radius, so that a larger shadow is
		42		// more rounded, but only if we are not already rounding the corners due to corner radius.
		43		lowp float size_factor = 0.5 * (minimum_shadow_radius / max(radius, minimum_shadow_radius));
		44
		45		lowp float shadowRadius = radius + size * size_factor;
		46
		47		lowp vec4 col = vec4(0.0);
		48
		49		// Calculate the shadow's distance field.
		50		lowp float shadow = sdf_rounded_rectangle(uv, aspect * inverse_scale, offset * inverse_scale, vec4(shadowRadius * inverse_scale));
		51		// Render it, interpolating the color over the distance.
		52		col = mix(col, shadowColor * sign(size), shadowColor.a * (1.0 - smoothstep(-size * 0.5, size * 0.5, shadow)));
		53
		54		// Calculate the main rectangle distance field.
		55		lowp float rect = sdf_rounded_rectangle(uv, aspect * inverse_scale, vec2(0.0), vec4(radius * inverse_scale));
		56
		57		lowp float g = fwidth(rect);
		58
		59		// First, remove anything that was rendered by the shadow if it is inside the rectangle.
		60		// This allows us to use colors with alpha without rendering artifacts.
		61		col = mix(col, vec4(0.0), 1.0 - smoothstep(0.001 - g, 0.001 + g, rect));
		62
		63		// Then, render it again but this time with the proper color and properly alpha blended.
		64		col = mix(col, color, color.a * (1.0 - smoothstep(0.001 - g, 0.001 + g, rect)));
		65
		66		gl_FragColor = col * opacity;
		67		}