Added transparent forward pass as third subpass, demonstrate preserve attachment

data/shaders/subpasses/gbuffer.frag

@@ -15,6 +15,15 @@ layout (location = 1) out vec4 outPosition;
 layout (location = 2) out vec4 outNormal;
 layout (location = 3) out vec4 outAlbedo;
 
+layout (constant_id = 0) const float NEAR_PLANE = 0.1f;
+layout (constant_id = 1) const float FAR_PLANE = 256.0f;
+
+float linearDepth(float depth)
+{
+	float z = depth * 2.0f - 1.0f; 
+	return (2.0f * NEAR_PLANE * FAR_PLANE) / (FAR_PLANE + NEAR_PLANE - z * (FAR_PLANE - NEAR_PLANE));	
+}
+
 void main() 
 {
 	outPosition = vec4(inWorldPos, 1.0);
@@ -23,7 +32,10 @@ void main()
 	N.y = -N.y;
 	outNormal = vec4(N, 1.0);
 
-	outAlbedo = vec4(inColor, 1.0);
+	outAlbedo.rgb = inColor;
+
+	// Store linearized depth in alpha component
+	outPosition.a = linearDepth(gl_FragCoord.z);
 
 	// Write color attachments to avoid undefined behaviour (validation error)
 	outColor = vec4(0.0);

data/shaders/subpasses/transparent.frag

@@ -0,0 +1,33 @@
+#version 450
+
+#extension GL_ARB_separate_shader_objects : enable
+#extension GL_ARB_shading_language_420pack : enable
+
+layout (input_attachment_index = 1, binding = 1) uniform subpassInput samplerPositionDepth;
+
+layout (location = 0) in vec3 inColor;
+layout (location = 1) in vec2 inUV;
+
+layout (location = 0) out vec4 outColor;
+
+layout (constant_id = 0) const float NEAR_PLANE = 0.1f;
+layout (constant_id = 1) const float FAR_PLANE = 256.0f;
+
+float linearDepth(float depth)
+{
+	float z = depth * 2.0f - 1.0f; 
+	return (2.0f * NEAR_PLANE * FAR_PLANE) / (FAR_PLANE + NEAR_PLANE - z * (FAR_PLANE - NEAR_PLANE));	
+}
+
+void main () 
+{
+	// Sample depth from deferred depth buffer and discard if obscured
+	float depth = subpassLoad(samplerPositionDepth).a;
+	if (linearDepth(gl_FragCoord.z) > depth)
+	{
+		discard;
+	};
+
+	outColor.rgb = vec3(0.0, 0.25, 0.86);
+	outColor.a = 0.5;
+}

data/shaders/subpasses/transparent.vert

@@ -0,0 +1,27 @@
+#version 450
+
+#extension GL_ARB_separate_shader_objects : enable
+#extension GL_ARB_shading_language_420pack : enable
+
+layout (location = 0) in vec4 inPos;
+layout (location = 1) in vec3 inColor;
+layout (location = 2) in vec3 inNormal;
+layout (location = 3) in vec2 inUV;
+
+layout (binding = 0) uniform UBO 
+{
+	mat4 projection;
+	mat4 model;
+	mat4 view;
+} ubo;
+
+layout (location = 0) out vec3 outColor;
+layout (location = 1) out vec2 outUV;
+
+void main () 
+{
+	outColor = inColor;
+	outUV = inUV;
+	
+	gl_Position = ubo.projection * ubo.view * ubo.model * vec4(inPos.xyz, 1.0);		
+}