Added shaders for PBR IBL irradiance cube map generation

data/shaders/pbribl/irradiancecube.frag

@@ -0,0 +1,37 @@
+// Generates an irradiance cube from an environment map using convolution
+
+#version 450
+
+layout (location = 0) in vec3 inPos;
+layout (location = 0) out vec4 outColor;
+layout (binding = 0) uniform samplerCube samplerEnv;
+
+layout(push_constant) uniform PushConsts {
+	layout (offset = 64) float deltaPhi;
+	layout (offset = 68) float deltaTheta;
+} consts;
+
+#define PI 3.1415926535897932384626433832795
+
+void main()
+{
+	vec3 N = normalize(inPos);
+	vec3 up = vec3(0.0, 1.0, 0.0);
+	vec3 right = normalize(cross(up, N));
+	up = cross(N, right);
+
+	const float TWO_PI = PI * 2.0;
+	const float HALF_PI = PI * 0.5;
+
+	vec3 color = vec3(0.0);
+	uint sampleCount = 0u;
+	for (float phi = 0.0; phi < TWO_PI; phi += consts.deltaPhi) {
+		for (float theta = 0.0; theta < HALF_PI; theta += consts.deltaTheta) {
+			vec3 tempVec = cos(phi) * right + sin(phi) * up;
+			vec3 sampleVector = cos(theta) * N + sin(theta) * tempVec;
+			color += texture(samplerEnv, sampleVector).rgb * cos(theta) * sin(theta);
+			sampleCount++;
+		}
+	}
+	outColor = vec4(PI * color / float(sampleCount), 1.0);
+}