ANother frustum culling question

Graphics and GPU Programming Programming

Started by dxdotnet1 November 08, 2004 02:02 AM

7 comments, last by dxdotnet1 19 years, 5 months ago

dxdotnet1

106

Author

November 08, 2004 02:02 AM

Whats wrong with my frustum cullinh code? Ive used the code bellow for my frustum culling test and it doesnt work


Matrix proj = new Matrix( );
Matrix view = new Matrix( );
		
proj = device.GetTransform( TransformType.Projection );
			view = device.GetTransform( TransformType.View );

Matrix comboMatrix = Matrix.Multiply( proj, view );
            
#region Plane extraction from combo matrix

//extract left plane
frustum[ 0 ].A = comboMatrix.M14 + comboMatrix.M11;
frustum[ 0 ].B = comboMatrix.M24 + comboMatrix.M21;
frustum[ 0 ].C = comboMatrix.M34 + comboMatrix.M31;
frustum[ 0 ].D = comboMatrix.M44 + comboMatrix.M41;
frustum[ 0 ].Normalize( );

//extract right plane
frustum[ 1 ].A = comboMatrix.M14 - comboMatrix.M11;
frustum[ 1 ].B = comboMatrix.M24 - comboMatrix.M21;
frustum[ 1 ].C = comboMatrix.M34 - comboMatrix.M31;
frustum[ 1 ].D = comboMatrix.M44 - comboMatrix.M41;
frustum[ 1 ].Normalize( );
			
//top clipping plane
frustum[ 2 ].A = comboMatrix.M14 - comboMatrix.M12;
frustum[ 2 ].B = comboMatrix.M24 - comboMatrix.M22;
frustum[ 2 ].C = comboMatrix.M34 - comboMatrix.M32;
frustum[ 2 ].D = comboMatrix.M44 - comboMatrix.M42;
frustum[ 2 ].Normalize( );
	
//bottom clipping plane
frustum[ 3 ].A = comboMatrix.M14 + comboMatrix.M12;
frustum[ 3 ].B = comboMatrix.M24 + comboMatrix.M22;
frustum[ 3 ].C = comboMatrix.M34 + comboMatrix.M32;
frustum[ 3 ].D = comboMatrix.M44 + comboMatrix.M42;
frustum[ 3 ].Normalize( );

//near clipping plane
frustum[ 4 ].A = comboMatrix.M14 + comboMatrix.M13;
frustum[ 4 ].B = comboMatrix.M24 + comboMatrix.M23;
frustum[ 4 ].C = comboMatrix.M34 + comboMatrix.M33;
frustum[ 4 ].D = comboMatrix.M44 + comboMatrix.M43;
frustum[ 4 ].Normalize( );

//Far clipping plane
frustum[ 5 ].A = comboMatrix.M14 - comboMatrix.M13;
frustum[ 5 ].B = comboMatrix.M24 - comboMatrix.M23;
frustum[ 5 ].C = comboMatrix.M34 - comboMatrix.M33;
frustum[ 5 ].D = comboMatrix.M44 - comboMatrix.M43;
frustum[ 5 ].Normalize( );

and i test my a certain Point using this code:


public static bool CheckPoint( float x,float y,float z )
{
	for(int i= 0; i < 6 ; i++ ) 
	{ 
          float d = frustum.A* x + frustum.B*y +  
                    frustum.C* z + frustum.D;
	  if( d <= 0 )						  	    return false;
	}
        return true;	
}

whats wrong with my code? [Edited by - Coder on November 9, 2004 2:44:27 AM]

sirob

1,181

November 08, 2004 04:38 AM

Use the D3DXPlaneDotCoord function instead of the A*x, B*y... part.

Sirob Yes.» - status: Work-O-Rama.

yuppies

116

November 09, 2004 02:03 AM

mind to teach me how to use that function?

show me some sample code on how to test my frustum planes and a vertex

yuppies

116

November 09, 2004 04:01 AM

i already tried using D3DXPlaneDotCoor function to no avail.
is my plane extraction correct?

kandemor

122

November 09, 2004 05:53 AM

My code for extract planes

g_pd3dDevice->GetTransform(D3DTS_PROJECTION, &proj);	g_pd3dDevice->GetTransform(D3DTS_WORLD, &world);	g_pd3dDevice->GetTransform(D3DTS_VIEW, &view);	// Combine the three matrices	clip = world * view * proj;	// Extract the numbers for the RIGHT plane 	frustum[0][0] = clip[ 3] - clip[ 0];	frustum[0][1] = clip[ 7] - clip[ 4];	frustum[0][2] = clip[11] - clip[ 8];	frustum[0][3] = clip[15] - clip[12];	//Normalize the result	t = sqrt( frustum[0][0] * frustum[0][0] + frustum[0][1] * frustum[0][1] + frustum[0][2] * frustum[0][2] );	frustum[0][0] /= t;	frustum[0][1] /= t;	frustum[0][2] /= t;	frustum[0][3] /= t;	// Extract the numbers for the LEFT plane	frustum[1][0] = clip[ 3] + clip[ 0];	frustum[1][1] = clip[ 7] + clip[ 4];	frustum[1][2] = clip[11] + clip[ 8];	frustum[1][3] = clip[15] + clip[12];	// Normalize the result	t = sqrt( frustum[1][0] * frustum[1][0] + frustum[1][1] * frustum[1][1] + frustum[1][2] * frustum[1][2] );	frustum[1][0] /= t;	frustum[1][1] /= t;	frustum[1][2] /= t;	frustum[1][3] /= t;	// Extract the BOTTOM plane	frustum[2][0] = clip[ 3] + clip[ 1];	frustum[2][1] = clip[ 7] + clip[ 5];	frustum[2][2] = clip[11] + clip[ 9];	frustum[2][3] = clip[15] + clip[13];	// Normalize the result	t = sqrt( frustum[2][0] * frustum[2][0] + frustum[2][1] * frustum[2][1] + frustum[2][2] * frustum[2][2] );	frustum[2][0] /= t;	frustum[2][1] /= t;	frustum[2][2] /= t;	frustum[2][3] /= t;	//Extract the TOP plane	frustum[3][0] = clip[ 3] - clip[ 1];	frustum[3][1] = clip[ 7] - clip[ 5];	frustum[3][2] = clip[11] - clip[ 9];	frustum[3][3] = clip[15] - clip[13];	// Normalize the result	t = sqrt( frustum[3][0] * frustum[3][0] + frustum[3][1] * frustum[3][1] + frustum[3][2] * frustum[3][2] );	frustum[3][0] /= t;	frustum[3][1] /= t;	frustum[3][2] /= t;	frustum[3][3] /= t;	// Extract the FAR plane	frustum[4][0] = clip[ 3] - clip[ 2];	frustum[4][1] = clip[ 7] - clip[ 6];	frustum[4][2] = clip[11] - clip[10];	frustum[4][3] = clip[15] - clip[14];	// Normalize the result	t = sqrt( frustum[4][0] * frustum[4][0] + frustum[4][1] * frustum[4][1] + frustum[4][2] * frustum[4][2] );	frustum[4][0] /= t;	frustum[4][1] /= t;	frustum[4][2] /= t;	frustum[4][3] /= t;	// Extract the NEAR plane	frustum[5][0] = clip[ 3] + clip[ 2];	frustum[5][1] = clip[ 7] + clip[ 6];	frustum[5][2] = clip[11] + clip[10];	frustum[5][3] = clip[15] + clip[14];	// Normalize the result	t = sqrt( frustum[5][0] * frustum[5][0] + frustum[5][1] * frustum[5][1] + frustum[5][2] * frustum[5][2] );	frustum[5][0] /= t;	frustum[5][1] /= t;	frustum[5][2] /= t;	frustum[5][3] /= t;

And my code to test a point:

bool Clipper::pointInFrustum(D3DVECTOR point){	for (int i=0;i<6;i++)	{		if (frustum[0]*point.x+frustum[1]*point.y+frustum[2]*point.z+frustum[3]<= 0 )			return false;	}	return true;}

Hope it will be useful to you.

VinCenT.

yuppies

116

November 09, 2004 07:41 PM

thanks. a couple of things i get confused. do i need to include the world matrix when getting the clip or its just the vew and projection?

lastly? DO i need to test the point againts 6 planes or stop when i alreadu encounter a <=0 value against a plane?
Example when i test the point against the first plane and got a negative result, do i still need to test the point against the rest of the plane or not? pls explain :)

SimmerD

1,210

November 10, 2004 12:24 AM

If a point is behind any one plane, you can stop at that point. Only if the point is inside all 6 planes is it potentially visible.

Does your normalize function also rescale the D component?

Here is mine for what it's worth...

    // Extract the numbers for the Far plane     mFrustum.mPlanes[ Shapes::Far ].mPlane.a = mComposite._14 - mComposite._13;    mFrustum.mPlanes[ Shapes::Far ].mPlane.b = mComposite._24 - mComposite._23;    mFrustum.mPlanes[ Shapes::Far ].mPlane.c = mComposite._34 - mComposite._33;    mFrustum.mPlanes[ Shapes::Far ].mPlane.d = mComposite._44 - mComposite._43;    D3DXPlaneNormalize( &mFrustum.mPlanes[ Shapes::Far ].mPlane, &mFrustum.mPlanes[ Shapes::Far ].mPlane );    mFrustum.mPlanes[ Shapes::Far ].mNormal = D3DXVECTOR3( mFrustum.mPlanes[ Shapes::Far ].mPlane.a,                                                           mFrustum.mPlanes[ Shapes::Far ].mPlane.b,                                                           mFrustum.mPlanes[ Shapes::Far ].mPlane.c );    mFrustum.mPlanes[ Shapes::Far ].mDistance = mFrustum.mPlanes[ Shapes::Far ].mPlane.d;

Game Development Journal

kandemor

122

November 10, 2004 02:24 AM

Here you can find all the information you need:

http://www2.ravensoft.com/users/ggribb/plane%20extraction.pdf
http://crownandcutlass.sourceforge.net/frustum.html

Bye!

VinCenT

dxdotnet1

106

Author

November 10, 2004 06:09 AM

tenks for your help guys.
i got it working now :)

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