Water Reflection Issue

I am having problems with my planar reflection to a water plane in my scene. For the most part I think I have got this correct including the projection of the scene (render texture) to the water plane itself. I have read through this thread as a as well as Yanns article. My issue arises when I modify the projection matrix to do the oblique culling (using the water plane) before the texture render. The depth of the rendered objects is totally screwed. I will show you a few pictures: In the below images I do not modify the projection matrix to do the oblique culling. This works perfectly but, as expected, I get artifacts on the water from certain angles. "Working" scene with no oblique technique "Working" scene render texture with no oblique culling If I modify the projection matrix my scene turns out like this: Broken scene with oblique technique used Broken scene render texture You can see in the broken scenes render texture that the depth is totally messed up. I don't get visual artifacts other than this problem with the depth of rendered items. Do I have to do something to the depth buffer before rendering the scene to the texture? I have reversed the cull mode before the texture render etc. The code I am using to modify the view matrix with a reflection matrix, make a clip plane in camera space and then modify the projection matrix to use the oblique frustum technique is:


HEMatrix Reflect, View, Proj, ViewReflect, Temp;
	HEVector Point, Normal, PP, PN, ClipPlane, q;
		
	Reflect.Identity();
	View.Identity();
	Proj.Identity();
	ViewReflect.Identity();
	Temp.Identity();
			
	// Use off-screen render target
	HADES->m_pRenderDevice->UseRenderTarget( App->m_RenderTargetID ); 

	// Get the current view and projection matrix
	HADES->m_pRenderDevice->GetMatrix( HEMAT_PPROJ0, Proj );
	HADES->m_pRenderDevice->GetMatrix( HEMAT_VIEW3D, View );

	/// Build and set reflection matrix on the XZ plane
	Reflect._22 = -1.0f;
	Reflect._42 = 2.0f * -2.0f;	
	ViewReflect = View * Reflect;
	HADES->m_pRenderDevice->SetMatrix( HEMAT_VIEW3D, ViewReflect );

	// Modify the projection matrix
	Point.Set( 0.0f, -2.0f, 0.0f, 1.0f );	// Point on plane
	Normal.Set( 0.0f, 1.0f, 0.0f, 1.0f );	// Water plane normal

	// Copy modified view matrix to temporary variable for 3X3 config.
	memcpy( &Temp._11, &ViewReflect._11, sizeof(float)*16 );	

	// Make temporary matrix 3X3 of ViewReflect
	Temp._14 = 0.0f;
	Temp._24 = 0.0f;
	Temp._34 = 0.0f;
	Temp._44 = 1.0f;
	Temp._41 = 0.0f;
	Temp._42 = 0.0f;
	Temp._43 = 0.0f;
    	
	PP = Point * ViewReflect;
	PN = Normal * Temp;
	PN.Normalise();

	// This is in camera space
	ClipPlane.Set( PP.x, PP.y, PP.z, -(PP*PN) );

	// Calculate the clip-space corner point opposite the clipping plane
	// as (sgn(clipPlane.x), sgn(clipPlane.y), 1, 1) and
	// transform it into camera space by multiplying it
	// by the inverse of the projection matrix
	
	q.x = App->sgn(ClipPlane.x) / Proj._11;
	q.y = App->sgn(ClipPlane.y) / Proj._22;
	q.z = 1.0f;
	q.w = (1.0f - Proj._33) / Proj._43;
	
	// Calculate the scaled plane vector
	HEVector c = ClipPlane * (1.0f / (ClipPlane * q));
			
	// Replace the third column of the projection matrix
	Proj._13 = c.x;
	Proj._23 = c.y;
	Proj._33 = c.z;
	Proj._43 = c.w;

	// Set this as the projection matrix
	HADES->m_pRenderDevice->SetMatrix( HEMAT_PPROJ0, Proj );

    // Store the modified projection matrix
    HADES->m_pRenderDevice->GetMatrix( HEMAT_PPROJ0, App->m_ModProj );

After this code I flip the cull mode and render the scene to a texture. After that I set the view and projection matrices back, reflip the culling order and then render the scene as normal to the back buffer. For the water plane I project this rendered texture on to it. The render texture comes out with what I think are depth related problems though. Can anyone help me [smile]? I am using DirectX 9. The matrix class is 4X4 and the vector class is 4D. The water level is (0.0f, -2.0f, 0.0f) and the water plane normal is of course (0.0f, 1.0f, 0.0f) [Edited by - __Daedalus__ on January 1, 2005 5:28:34 PM]

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