frustum.cpp

用opengl实现的bsp管理3D场景的算法

		{
			// The distance was greater than the radius so the sphere is outside of the frustum
			return false;
		}
	}
	
	// The sphere was inside of the frustum!
	return true;
}


///////////////////////////////// CUBE IN FRUSTUM \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This determines if a cube is in or around our frustum by it's center and 1/2 it's length
/////
///////////////////////////////// CUBE IN FRUSTUM \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

bool CFrustum::CubeInFrustum( float x, float y, float z, float size )
{
	// Basically, what is going on is, that we are given the center of the cube,
	// and half the length.  Think of it like a radius.  Then we checking each point
	// in the cube and seeing if it is inside the frustum.  If a point is found in front
	// of a side, then we skip to the next side.  If we get to a plane that does NOT have
	// a point in front of it, then it will return false.

	// *Note* - This will sometimes say that a cube is inside the frustum when it isn't.
	// This happens when all the corners of the bounding box are not behind any one plane.
	// This is rare and shouldn't effect the overall rendering speed.

	for(int i = 0; i < 6; i++ )
	{
		if(m_Frustum[i][A] * (x - size) + m_Frustum[i][B] * (y - size) + m_Frustum[i][C] * (z - size) + m_Frustum[i][D] > 0)
		   continue;
		if(m_Frustum[i][A] * (x + size) + m_Frustum[i][B] * (y - size) + m_Frustum[i][C] * (z - size) + m_Frustum[i][D] > 0)
		   continue;
		if(m_Frustum[i][A] * (x - size) + m_Frustum[i][B] * (y + size) + m_Frustum[i][C] * (z - size) + m_Frustum[i][D] > 0)
		   continue;
		if(m_Frustum[i][A] * (x + size) + m_Frustum[i][B] * (y + size) + m_Frustum[i][C] * (z - size) + m_Frustum[i][D] > 0)
		   continue;
		if(m_Frustum[i][A] * (x - size) + m_Frustum[i][B] * (y - size) + m_Frustum[i][C] * (z + size) + m_Frustum[i][D] > 0)
		   continue;
		if(m_Frustum[i][A] * (x + size) + m_Frustum[i][B] * (y - size) + m_Frustum[i][C] * (z + size) + m_Frustum[i][D] > 0)
		   continue;
		if(m_Frustum[i][A] * (x - size) + m_Frustum[i][B] * (y + size) + m_Frustum[i][C] * (z + size) + m_Frustum[i][D] > 0)
		   continue;
		if(m_Frustum[i][A] * (x + size) + m_Frustum[i][B] * (y + size) + m_Frustum[i][C] * (z + size) + m_Frustum[i][D] > 0)
		   continue;

		// If we get here, it isn't in the frustum
		return false;
	}

	return true;
}


///////////////////////////////// BOX IN FRUSTUM \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This determines if a BOX is in or around our frustum by it's min and max points
/////
///////////////////////////////// BOX IN FRUSTUM \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

bool CFrustum::BoxInFrustum( float x, float y, float z, float x2, float y2, float z2)
{
	// Go through all of the corners of the box and check then again each plane
	// in the frustum.  If all of them are behind one of the planes, then it most
	// like is not in the frustum.
	for(int i = 0; i < 6; i++ )
	{
		if(m_Frustum[i][A] * x  + m_Frustum[i][B] * y  + m_Frustum[i][C] * z  + m_Frustum[i][D] > 0)  continue;
		if(m_Frustum[i][A] * x2 + m_Frustum[i][B] * y  + m_Frustum[i][C] * z  + m_Frustum[i][D] > 0)  continue;
		if(m_Frustum[i][A] * x  + m_Frustum[i][B] * y2 + m_Frustum[i][C] * z  + m_Frustum[i][D] > 0)  continue;
		if(m_Frustum[i][A] * x2 + m_Frustum[i][B] * y2 + m_Frustum[i][C] * z  + m_Frustum[i][D] > 0)  continue;
		if(m_Frustum[i][A] * x  + m_Frustum[i][B] * y  + m_Frustum[i][C] * z2 + m_Frustum[i][D] > 0)  continue;
		if(m_Frustum[i][A] * x2 + m_Frustum[i][B] * y  + m_Frustum[i][C] * z2 + m_Frustum[i][D] > 0)  continue;
		if(m_Frustum[i][A] * x  + m_Frustum[i][B] * y2 + m_Frustum[i][C] * z2 + m_Frustum[i][D] > 0)  continue;
		if(m_Frustum[i][A] * x2 + m_Frustum[i][B] * y2 + m_Frustum[i][C] * z2 + m_Frustum[i][D] > 0)  continue;

		// If we get here, it isn't in the frustum
		return false;
	}

	// Return a true for the box being inside of the frustum
	return true;
}


///////////////////////////////// RENDER DEBUG LINES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This goes through all of the lines that we stored in our list and draws them
/////
///////////////////////////////// RENDER DEBUG LINES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CDebug::RenderDebugLines()				// This renders all of the lines
{
    glDisable(GL_TEXTURE_2D);

	glBegin(GL_LINES);						// Start rendering lines

		glColor3ub(255, 255, 0);			// Turn the lines yellow

		// Go through the whole list of lines stored in the vector m_vLines.
		for(unsigned int i = 0; i < m_vLines.size(); i++)
		{
			// Pass in the current point to be rendered as part of a line
			glVertex3f(m_vLines[i].x, m_vLines[i].y, m_vLines[i].z);
		}	

	glEnd();				
}


///////////////////////////////// ADD DEBUG LINE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This adds a debug LINE to the stack of lines
/////
///////////////////////////////// ADD DEBUG LINE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CDebug::AddDebugLine(CVector3 vPoint1, CVector3 vPoint2)
{
	// Add the 2 points that make up the line into our line list.
	m_vLines.push_back(vPoint1);
	m_vLines.push_back(vPoint2);
}


///////////////////////////////// ADD DEBUG BOX \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This adds a debug BOX to the stack of lines
/////
///////////////////////////////// ADD DEBUG BOX\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CDebug::AddDebugBox(CVector3 vCenter, float width, float height, float depth)
{
	// So we can work with the code better, we divide the dimensions in half.
	// That way we can create the box from the center outwards.
	width /= 2.0f;	height /= 2.0f;	depth /= 2.0f;

	// Below we create all the 8 points so it will be easier to input the lines
	// of the box.  With the dimensions we calculate the points.
	CVector3 vTopLeftFront( vCenter.x - width, vCenter.y + height, vCenter.z + depth);
	CVector3 vTopLeftBack(  vCenter.x - width, vCenter.y + height, vCenter.z - depth);
	CVector3 vTopRightBack( vCenter.x + width, vCenter.y + height, vCenter.z - depth);
	CVector3 vTopRightFront(vCenter.x + width, vCenter.y + height, vCenter.z + depth);

	CVector3 vBottom_LeftFront( vCenter.x - width, vCenter.y - height, vCenter.z + depth);
	CVector3 vBottom_LeftBack(  vCenter.x - width, vCenter.y - height, vCenter.z - depth);
	CVector3 vBottomRightBack( vCenter.x + width, vCenter.y - height, vCenter.z - depth);
	CVector3 vBottomRightFront(vCenter.x + width, vCenter.y - height, vCenter.z + depth);

	////////// TOP LINES ////////// 

	// Store the top front line of the box
	m_vLines.push_back(vTopLeftFront);		m_vLines.push_back(vTopRightFront);

	// Store the top back line of the box
	m_vLines.push_back(vTopLeftBack);  		m_vLines.push_back(vTopRightBack);

	// Store the top left line of the box
	m_vLines.push_back(vTopLeftFront);		m_vLines.push_back(vTopLeftBack);

	// Store the top right line of the box
	m_vLines.push_back(vTopRightFront);		m_vLines.push_back(vTopRightBack);

	////////// BOTTOM LINES ////////// 

	// Store the bottom front line of the box
	m_vLines.push_back(vBottom_LeftFront);	m_vLines.push_back(vBottomRightFront);

	// Store the bottom back line of the box
	m_vLines.push_back(vBottom_LeftBack);	m_vLines.push_back(vBottomRightBack);

	// Store the bottom left line of the box
	m_vLines.push_back(vBottom_LeftFront);	m_vLines.push_back(vBottom_LeftBack);

	// Store the bottom right line of the box
	m_vLines.push_back(vBottomRightFront);	m_vLines.push_back(vBottomRightBack);

	////////// SIDE LINES ////////// 

	// Store the bottom front line of the box
	m_vLines.push_back(vTopLeftFront);		m_vLines.push_back(vBottom_LeftFront);

	// Store the back left line of the box
	m_vLines.push_back(vTopLeftBack);		m_vLines.push_back(vBottom_LeftBack);

	// Store the front right line of the box
	m_vLines.push_back(vTopRightBack);		m_vLines.push_back(vBottomRightBack);

	// Store the front left line of the box
	m_vLines.push_back(vTopRightFront);		m_vLines.push_back(vBottomRightFront);
}


/////////////////////////////////////////////////////////////////////////////////
//
// * QUICK NOTES * 
//
// This code was taken directly from the frustum tutorial located at www.GameTutorials.com.
// Most of the large block of comments were taken out.  If you want to learn more about
// this frustum code, visit our site.  We added BoxInFrustum() to this file so that we
// could check against bounding boxes.
//
//
// Ben Humphrey
// Game Programmer
// [e-mail]
// www.GameTutorials.com
//
//