1 files changed, 99 insertions, 0 deletions
diff --git a/tier2/camerautils.cpp b/tier2/camerautils.cpp
new file mode 100644
index 0000000..41d1dc7
--- /dev/null
+++ b/tier2/camerautils.cpp
@@ -0,0 +1,99 @@
+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose: 
+//
+//=============================================================================
+#include "tier2/camerautils.h"
+#include "tier0/dbg.h"
+#include "mathlib/vector.h"
+#include "mathlib/vmatrix.h"
+#include "tier2/tier2.h"
+
+// memdbgon must be the last include file in a .cpp file!!!
+#include "tier0/memdbgon.h"
+
+
+//-----------------------------------------------------------------------------
+// accessors for generated matrices
+//-----------------------------------------------------------------------------
+void ComputeViewMatrix( matrix3x4_t *pWorldToCamera, const Camera_t &camera )
+{
+	matrix3x4_t transform;
+	AngleMatrix( camera.m_angles, camera.m_origin, transform );
+
+	VMatrix matRotate( transform );
+	VMatrix matRotateZ;
+	MatrixBuildRotationAboutAxis( matRotateZ, Vector(0,0,1), -90 );
+	MatrixMultiply( matRotate, matRotateZ, matRotate );
+
+	VMatrix matRotateX;
+	MatrixBuildRotationAboutAxis( matRotateX, Vector(1,0,0), 90 );
+	MatrixMultiply( matRotate, matRotateX, matRotate );
+	transform = matRotate.As3x4();
+
+	MatrixInvert( transform, *pWorldToCamera );
+}
+
+void ComputeViewMatrix( VMatrix *pWorldToCamera, const Camera_t &camera )
+{
+	matrix3x4_t transform, invTransform;
+	AngleMatrix( camera.m_angles, camera.m_origin, transform );
+
+	VMatrix matRotate( transform );
+	VMatrix matRotateZ;
+	MatrixBuildRotationAboutAxis( matRotateZ, Vector(0,0,1), -90 );
+	MatrixMultiply( matRotate, matRotateZ, matRotate );
+
+	VMatrix matRotateX;
+	MatrixBuildRotationAboutAxis( matRotateX, Vector(1,0,0), 90 );
+	MatrixMultiply( matRotate, matRotateX, matRotate );
+	transform = matRotate.As3x4();
+
+	MatrixInvert( transform, invTransform );
+	*pWorldToCamera = invTransform;
+}
+
+void ComputeProjectionMatrix( VMatrix *pCameraToProjection, const Camera_t &camera, int width, int height )
+{
+	float flFOV = camera.m_flFOV;
+	float flZNear = camera.m_flZNear;
+	float flZFar = camera.m_flZFar;
+	float flApsectRatio = (float)width / (float)height;
+
+//	MatrixBuildPerspective( proj, flFOV, flFOV * flApsectRatio, flZNear, flZFar );
+
+#if 1
+	float halfWidth = tan( flFOV * M_PI / 360.0 );
+	float halfHeight = halfWidth / flApsectRatio;
+#else
+	float halfHeight = tan( flFOV * M_PI / 360.0 );
+	float halfWidth = flApsectRatio * halfHeight;
+#endif
+	memset( pCameraToProjection, 0, sizeof( VMatrix ) );
+	pCameraToProjection->m[0][0]  = 1.0f / halfWidth;
+	pCameraToProjection->m[1][1]  = 1.0f / halfHeight;
+	pCameraToProjection->m[2][2] = flZFar / ( flZNear - flZFar );
+	pCameraToProjection->m[3][2] = -1.0f;
+	pCameraToProjection->m[2][3] = flZNear * flZFar / ( flZNear - flZFar );
+}
+
+
+//-----------------------------------------------------------------------------
+// Computes the screen space position given a screen size
+//-----------------------------------------------------------------------------
+void ComputeScreenSpacePosition( Vector2D *pScreenPosition, const Vector &vecWorldPosition, 
+	const Camera_t &camera, int width, int height )
+{
+	VMatrix view, proj, viewproj;
+	ComputeViewMatrix( &view, camera );
+	ComputeProjectionMatrix( &proj, camera, width, height );
+	MatrixMultiply( proj, view, viewproj );
+
+	Vector vecScreenPos;
+	Vector3DMultiplyPositionProjective( viewproj, vecWorldPosition, vecScreenPos );
+
+	pScreenPosition->x = ( vecScreenPos.x + 1.0f ) * width / 2.0f;
+	pScreenPosition->y = ( -vecScreenPos.y + 1.0f ) * height / 2.0f;
+}
+
+