From ddf92b39c76408836d4a54e1f7202f44f71fe63d Mon Sep 17 00:00:00 2001
From: Andrzej Kapolka <drzej.k@gmail.com>
Date: Sun, 8 Sep 2013 17:52:35 -0700
Subject: [PATCH] Fix for off-axis ambient occlusion.

---
 .../resources/shaders/ambient_occlusion.frag  |  3 +--
 interface/src/Application.cpp                 | 22 ++++++++++++-------
 interface/src/Application.h                   |  4 ++++
 .../src/renderer/AmbientOcclusionEffect.cpp   |  2 +-
 4 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/interface/resources/shaders/ambient_occlusion.frag b/interface/resources/shaders/ambient_occlusion.frag
index 4e87ac3221..b3a054cc67 100644
--- a/interface/resources/shaders/ambient_occlusion.frag
+++ b/interface/resources/shaders/ambient_occlusion.frag
@@ -44,8 +44,7 @@ float texCoordToViewSpaceZ(vec2 texCoord) {
 // given a texture coordinate, returns the 3D view space coordinate
 vec3 texCoordToViewSpace(vec2 texCoord) {
     float z = texCoordToViewSpaceZ(texCoord);
-    return vec3(((texCoord * 2.0 - vec2(1.0 - gl_ProjectionMatrix[2][0], 1.0)) *
-        (rightTop - leftBottom) + rightTop + leftBottom) * z / (-2.0 * near), z);
+    return vec3((leftBottom + texCoord * (rightTop - leftBottom)) * (-z / near), z);
 }
 
 void main(void) {
diff --git a/interface/src/Application.cpp b/interface/src/Application.cpp
index a473469734..ea61179057 100644
--- a/interface/src/Application.cpp
+++ b/interface/src/Application.cpp
@@ -438,7 +438,7 @@ void Application::updateProjectionMatrix() {
     
     float left, right, bottom, top, nearVal, farVal;
     glm::vec4 nearClipPlane, farClipPlane;
-    _viewFrustum.computeOffAxisFrustum(left, right, bottom, top, nearVal, farVal, nearClipPlane, farClipPlane);
+    computeOffAxisFrustum(left, right, bottom, top, nearVal, farVal, nearClipPlane, farClipPlane);
     
     // If we're in Display Frustum mode, then we want to use the slightly adjust near/far clip values of the
     // _viewFrustumOffsetCamera, so that we can see more of the application content in the application's frustum
@@ -446,13 +446,6 @@ void Application::updateProjectionMatrix() {
         nearVal = _viewFrustumOffsetCamera.getNearClip();
         farVal = _viewFrustumOffsetCamera.getFarClip();
     }
-    
-    // when mirrored, we must flip left and right
-    if (Menu::getInstance()->isOptionChecked(MenuOption::Mirror)) {
-        float tmp = left;
-        left = -right;
-        right = -tmp;
-    }
     glFrustum(left, right, bottom, top, nearVal, farVal);
     
     glMatrixMode(GL_MODELVIEW);
@@ -2144,6 +2137,19 @@ void Application::setupWorldLight(Camera& whichCamera) {
     glMateriali(GL_FRONT, GL_SHININESS, 96);
 }
 
+void Application::computeOffAxisFrustum(float& left, float& right, float& bottom, float& top, float& near,
+    float& far, glm::vec4& nearClipPlane, glm::vec4& farClipPlane) const {
+    
+    _viewFrustum.computeOffAxisFrustum(left, right, bottom, top, near, far, nearClipPlane, farClipPlane);
+    
+    // when mirrored, we must flip left and right
+    if (Menu::getInstance()->isOptionChecked(MenuOption::Mirror)) {
+        float tmp = left;
+        left = -right;
+        right = -tmp;
+    }
+}
+
 void Application::displaySide(Camera& whichCamera) {
     // transform by eye offset
 
diff --git a/interface/src/Application.h b/interface/src/Application.h
index 0630d3cbca..8bb3106375 100644
--- a/interface/src/Application.h
+++ b/interface/src/Application.h
@@ -135,6 +135,10 @@ public:
     
     void setupWorldLight(Camera& whichCamera);
 
+    /// Computes the off-axis frustum parameters for the view frustum, taking mirroring into account.
+    void computeOffAxisFrustum(float& left, float& right, float& bottom, float& top, float& near,
+        float& far, glm::vec4& nearClipPlane, glm::vec4& farClipPlane) const;
+
     virtual void nodeAdded(Node* node);
     virtual void nodeKilled(Node* node);
     virtual void packetSentNotification(ssize_t length);
diff --git a/interface/src/renderer/AmbientOcclusionEffect.cpp b/interface/src/renderer/AmbientOcclusionEffect.cpp
index 2169ec00af..907ec7a863 100644
--- a/interface/src/renderer/AmbientOcclusionEffect.cpp
+++ b/interface/src/renderer/AmbientOcclusionEffect.cpp
@@ -103,7 +103,7 @@ void AmbientOcclusionEffect::render() {
     
     float left, right, bottom, top, nearVal, farVal;
     glm::vec4 nearClipPlane, farClipPlane;
-    Application::getInstance()->getViewFrustum()->computeOffAxisFrustum(
+    Application::getInstance()->computeOffAxisFrustum(
         left, right, bottom, top, nearVal, farVal, nearClipPlane, farClipPlane);
     
     _occlusionProgram->bind();