Started on ambient occlusion shader.

interface/resources/shaders/ambient_occlusion.frag

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+#version 120
+
+//
+//  ambient_occlusion.frag
+//  fragment shader
+//
+//  Created by Andrzej Kapolka on 7/5/13.
+//  Copyright (c) 2013 High Fidelity, Inc. All rights reserved.
+//
+
+// the depth texture
+uniform sampler2D depth;
+
+// the distance to the near clip plane
+uniform float near;
+
+// the distance to the far clip plane
+uniform float far;
+
+// the left and bottom edges of the view window
+uniform vec2 leftBottom;
+
+// the right and top edges of the view window
+uniform vec2 rightTop;
+
+// given a texture coordinate, returns the 3D view space coordinate
+vec3 texCoordToViewSpace(vec2 texCoord) {
+    float z = (far * near) / (texture2D(depth, texCoord).r * (far - near) - far);
+    return vec3(((texCoord * 2.0 - vec2(1.0, 1.0)) * (rightTop - leftBottom) + rightTop + leftBottom) * z / (-2.0 * near), z);
+}
+
+void main(void) {
+    gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
+}