protected void CalculateProjectionParameters( out Real vpLeft, out Real vpRight, out Real vpBottom, out Real vpTop )
{
if ( _customProjectionMatrix )
{
// Convert clipspace corners to camera space
Matrix4 invProj = _projectionMatrix.Inverse();
Vector3 topLeft = new Vector3( -0.5f, 0.5f, 0.0f );
Vector3 bottomRight = new Vector3( 0.5f, -0.5f, 0.0f );
topLeft = invProj * topLeft;
bottomRight = invProj * bottomRight;
vpLeft = topLeft.x;
vpTop = topLeft.y;
vpRight = bottomRight.x;
vpBottom = bottomRight.y;
}
else if ( _frustumExtentsManuallySet )
{
vpLeft = _left;
vpRight = _right;
vpTop = _top;
vpBottom = _bottom;
}
// Calculate general projection parameters
else if ( ProjectionType == Projection.Perspective )
{
// Calculate general projection parameters
float thetaY = _fieldOfView * 0.5f;
float tanThetaY = Utility.Tan( thetaY );
float tanThetaX = tanThetaY * _aspectRatio;
// Unknown how to apply frustum offset to orthographic camera, just ignore here
float nearFocal = _nearDistance / _focalLength;
float nearOffsetX = _frustumOffset.x * nearFocal;
float nearOffsetY = _frustumOffset.y * nearFocal;
float half_w = tanThetaX * _nearDistance;
float half_h = tanThetaY * _nearDistance;
vpLeft = -half_w + nearOffsetX;
vpRight = +half_w + nearOffsetX;
vpBottom = -half_h + nearOffsetY;
vpTop = +half_h + nearOffsetY;
_left = vpLeft;
_right = vpRight;
_top = vpTop;
_bottom = vpBottom;
}
else //if (ProjectionType == Projection.Orthographic)
{
// Unknown how to apply frustum offset to orthographic camera, just ignore here
float half_w = OrthoWindowWidth * 0.5f;
float half_h = OrthoWindowHeight * 0.5f;
vpLeft = -half_w;
vpRight = +half_w;
vpBottom = -half_h;
vpTop = +half_h;
_left = vpLeft;
_right = vpRight;
_top = vpTop;
_bottom = vpBottom;
}
}
