render: SSAO

internal/asset/shader/world/ssao.frag

@@ -0,0 +1,78 @@
+#version 330
+
+#define SSAO_SAMPLE_COUNT 32
+const float radius = 0.5, bias = 0;
+
+uniform vec3 viewPos;
+uniform mat4 view, projection;
+uniform float time; // current time in seconds, for extra noise
+
+uniform sampler2D rand;
+uniform vec2      randSize; // in pixels
+
+// SSAO samples (normalized, in tangent space)
+layout (std140) uniform uboSamples {
+	vec3 samples[SSAO_SAMPLE_COUNT];
+};
+
+// G-Buffers
+uniform sampler2D gPos;
+uniform sampler2D gNorm;
+// Fragment information from G-Buffers
+vec3 fragPos; // World position
+vec3 fragNormal; // World normal
+float fragDepthView;
+
+
+in vec2 fragPosScreen;
+layout (location = 0) out float output;
+
+
+// A random number generator from the web.
+// https://stackoverflow.com/questions/12964279/whats-the-origin-of-this-glsl-rand-one-liner
+float whatever(vec2 co){
+  return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
+}
+
+
+void loadGBuffer() {
+	vec4 fragGNormal = texture(gNorm, fragPosScreen);
+	fragNormal = fragGNormal.xyz;
+	if (fragNormal == vec3(0.0f, 0.0f, 0.0f))
+		discard;
+
+	vec4 fragGPos = texture(gPos, fragPosScreen);
+	fragPos = fragGPos.xyz + viewPos;
+	fragDepthView = fragGPos.w;
+	gl_FragDepth = fragGPos.w * 0.5 + 0.5;
+}
+
+
+void main() {
+
+	loadGBuffer();
+
+	vec4 randval = texture(rand, gl_FragCoord.xy / randSize);
+
+	vec3 tangent   = normalize(randval.xyz - fragNormal*dot(randval.xyz, fragNormal));
+	vec3 bitangent = cross(fragNormal, tangent);
+	mat3 TBN       = mat3(tangent, bitangent, fragNormal);
+
+	float occlusion = 0;
+	for (int i = 0; i < SSAO_SAMPLE_COUNT; i++) {
+		vec3 samplePos = TBN * samples[i];
+		samplePos = fragPos + samplePos * radius;
+
+		vec4 viewpos = view * vec4(samplePos, 1.0);
+
+		vec4 ndcpos = projection * viewpos;
+		ndcpos.xyz /= ndcpos.w;
+
+		float sampleDepth = texture(gPos, ndcpos.xy*0.5 + 0.5).w;
+
+		float rangeCheck = smoothstep(0.0, 1.0, radius / abs(fragDepthView - sampleDepth));
+		occlusion       += (sampleDepth >= viewpos.z/viewpos.w + bias ? 1.0 : 0.0) * rangeCheck; 
+	}
+
+	output = 1.0 - (occlusion / SSAO_SAMPLE_COUNT);
+}