From ce69f27f321d6d47a1d67f0b0517d88eee25cbe3 Mon Sep 17 00:00:00 2001
From: yunfeibai <byf1658@gmail.com>
Date: Wed, 8 Feb 2017 11:34:38 -0800
Subject: [PATCH] Modify the depth buffer value in TinyRenderer to be
 consistent as in OpenGL.

---
 examples/CommonInterfaces/CommonCameraInterface.h     |  3 +++
 examples/OpenGLWindow/SimpleCamera.cpp                | 10 ++++++++++
 examples/OpenGLWindow/SimpleCamera.h                  |  5 ++++-
 .../SharedMemory/TinyRendererVisualShapeConverter.cpp | 11 ++++++++++-
 4 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/examples/CommonInterfaces/CommonCameraInterface.h b/examples/CommonInterfaces/CommonCameraInterface.h
index 813aa4344..88db58685 100644
--- a/examples/CommonInterfaces/CommonCameraInterface.h
+++ b/examples/CommonInterfaces/CommonCameraInterface.h
@@ -36,6 +36,9 @@ struct CommonCameraInterface
 
 	virtual void	setAspectRatio(float ratio) = 0;
 	virtual float	getAspectRatio() const = 0;
+    
+    virtual float getCameraFrustumFar() const = 0;
+    virtual float getCameraFrustumNear() const = 0;
 };
 
 #endif //COMMON_CAMERA_INTERFACE_H
diff --git a/examples/OpenGLWindow/SimpleCamera.cpp b/examples/OpenGLWindow/SimpleCamera.cpp
index 4b0b27164..93838a212 100644
--- a/examples/OpenGLWindow/SimpleCamera.cpp
+++ b/examples/OpenGLWindow/SimpleCamera.cpp
@@ -383,3 +383,13 @@ float	SimpleCamera::getAspectRatio() const
 {
 	return m_data->m_aspect;
 }
+
+float SimpleCamera::getCameraFrustumFar() const
+{
+    return m_data->m_frustumZFar;
+}
+
+float SimpleCamera::getCameraFrustumNear() const
+{
+    return m_data->m_frustumZNear;
+}
diff --git a/examples/OpenGLWindow/SimpleCamera.h b/examples/OpenGLWindow/SimpleCamera.h
index 5a61a729f..b186759c8 100644
--- a/examples/OpenGLWindow/SimpleCamera.h
+++ b/examples/OpenGLWindow/SimpleCamera.h
@@ -47,6 +47,9 @@ struct SimpleCamera : public CommonCameraInterface
 
 	virtual void	setAspectRatio(float ratio);
 	virtual float	getAspectRatio() const;
+    
+    virtual float getCameraFrustumFar() const;
+    virtual float getCameraFrustumNear() const;
 };
 
-#endif //SIMPLE_CAMERA_H
\ No newline at end of file
+#endif //SIMPLE_CAMERA_H
diff --git a/examples/SharedMemory/TinyRendererVisualShapeConverter.cpp b/examples/SharedMemory/TinyRendererVisualShapeConverter.cpp
index 5ae682fc2..cfe25c938 100644
--- a/examples/SharedMemory/TinyRendererVisualShapeConverter.cpp
+++ b/examples/SharedMemory/TinyRendererVisualShapeConverter.cpp
@@ -958,7 +958,16 @@ void TinyRendererVisualShapeConverter::copyCameraImageData(unsigned char* pixels
         {
 			if (depthBuffer)
 			{
-				depthBuffer[i] = m_data->m_depthBuffer[i+startPixelIndex];
+                float distance = -m_data->m_depthBuffer[i+startPixelIndex];
+                float farPlane = m_data->m_camera.getCameraFrustumFar();
+                float nearPlane = m_data->m_camera.getCameraFrustumNear();
+                
+                btClamp(distance,nearPlane,farPlane);
+                
+                // the depth buffer value is between 0 and 1
+                float a = farPlane / (farPlane - nearPlane);
+                float b = farPlane * nearPlane / (nearPlane - farPlane);
+                depthBuffer[i] = a + b / distance;
 			}
 			if (segmentationMaskBuffer)
             {