Inverse Projection Calculation - Philips DirectX Visualizer User Manual

DirectX Visualizer
Z-buffer values within the range of interest. Any values outside the range of interest are clipped to the
closest extreme of the range of interest.
Option name Option name Option name Option name
ZNearInterest
ZNearInterestDownKey
ZNearInterestUpKey
ZFarInterest
ZFarInterestDownKey
ZFarInterestUpKey
6.12 6.12 6.12 6.12

Inverse projection calculation

By default the Visualizer will use the inverse of the Direct3D projection matrix to calculate the Z
coordinates from the value in the Z-buffer. If the projection matrix cannot be inverted, an
approximation will be used instead. The Visualizer will write a warning message about this to the log if
logging is enabled (see Figure 6). It is recommended to test the application at least once with logging
enabled to see if this warning is given.
End of InitShaders
Warning: inverse projection matrix not valid; using approximation.
DllMain DLL_THREAD_ATTACH
Warning: Switched back to using inverse projection matrix.
DllMain DLL_THREAD_DETACH
If this warning is generated while the application is showing a 3D scene, then the approximation needs
to be tuned to still result in an acceptable 3D effect. For this purpose DynamicZtoD can be set to 0,
which will force the Visualizer to always use the approximation and allow you to determine an
acceptable FarNearRatio. The value of FarNearRatio only influences the approximation and has no
effect if the inverse projection matrix is used.
To determine the appropriate value for FarNearRatio it is recommended to:
1. run the application with EnableLogging=1, DynamicZtoD=0, EnableDepthTuningHelp=1 and
ZRange keys defined to usable values
2. change the FarNearRatio using the ZRangeUpKey and ZRangeDownKey to find a satisfactory
value
3. read the last used FarNearRatio value from the log file
4. set the chosen FarNearRatio value in the configuration file
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Possible values Possible values Possible values Possible values Default value Default value Default value Default value
floating point value 0.0
between 0.0 and
1.0
key disabled
key disabled
floating point value 1.0
between 0.0 and
1.0
key disabled
key disabled
Figure 6: log file fragment including warning
Description Description Description Description
Smallest Z-buffer value of interest
Key that decreases ZNearInterest
Key that increases ZNearInterest
Largest Z-buffer value of interest
Key that decreases ZFarInterest
Key that increases ZFarInterest
3D Solutions
01 April 2009
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