anki-3d-engine/programs/DepthDownscale.ankiprog

<!-- 
Copyright (C) 2009-2018, Panagiotis Christopoulos Charitos and contributors.
All rights reserved.
Code licensed under the BSD License.
http://www.anki3d.org/LICENSE
-->
<shaderProgram>
	<mutators>
		<mutator name="TYPE" values="0 1"/> <!-- 0: write to depth&color, 1: write to depth -->
		<mutator name="SAMPLE_RESOLVE_TYPE" values="0 1 2"/> <!-- 0: average, 1: min, 2: max -->
	</mutators>

	<shaders>
		<shader type="vert">
			<source><![CDATA[
#include "shaders/QuadVert.glsl"
			]]></source>
		</shader>

		<shader type="frag">
			<source><![CDATA[
#include "shaders/Common.glsl"

#define AVG 0
#define MIN 1
#define MAX 2

layout(ANKI_TEX_BINDING(0, 0)) uniform sampler2D u_depthRt;

layout(location = 0) in vec2 in_uv;

layout(location = 0) out float out_color;

void main()
{
	vec4 depths = textureGather(u_depthRt, in_uv, 0);

#if SAMPLE_RESOLVE_TYPE == MIN
	vec2 mind2 = min(depths.xy, depths.zw);
	out_color = min(mind2.x, mind2.y);
#elif SAMPLE_RESOLVE_TYPE == MAX
	vec2 max2 = max(depths.xy, depths.zw);
	out_color = max(max2.x, max2.y);
#elif SAMPLE_RESOLVE_TYPE == AVG
	out_color = dot(depths, vec4(1.0 / 4.0));
#else
#	error See file
#endif

#if TYPE == 0
	gl_FragDepth = out_color;
#endif
}
			]]></source>
		</shader>
	</shaders>
</shaderProgram>