public void GetShadowCamera( SceneManager sceneManager, Camera camera, Viewport viewport, Light light,
Camera textureCamera, int iteration )
{
Vector3 pos, dir;
Quaternion q;
// reset custom view / projection matrix in case already set
textureCamera.SetCustomViewMatrix( false );
textureCamera.SetCustomProjectionMatrix( false );
textureCamera.Near = light.DeriveShadowNearClipDistance( camera );
textureCamera.Far = light.DeriveShadowFarClipDistance( camera );
// get the shadow frustum's far distance
var shadowDist = light.ShadowFarDistance;
if ( shadowDist == 0.0f )
{
// need a shadow distance, make one up
shadowDist = camera.Near*300;
}
var shadowOffset = shadowDist*sceneManager.ShadowDirectionalLightTextureOffset;
// Directional lights
if ( light.Type == LightType.Directional )
{
// set up the shadow texture
// Set ortho projection
textureCamera.ProjectionType = Projection.Orthographic;
// set ortho window so that texture covers far dist
textureCamera.SetOrthoWindow( shadowDist*2, shadowDist*2 );
// Calculate look at position
// We want to look at a spot shadowOffset away from near plane
// 0.5 is a litle too close for angles
var target = camera.DerivedPosition + ( camera.DerivedDirection*shadowOffset );
// Calculate direction, which same as directional light direction
dir = -light.DerivedDirection; // backwards since point down -z
dir.Normalize();
// Calculate position
// We want to be in the -ve direction of the light direction
// far enough to project for the dir light extrusion distance
pos = target + dir*sceneManager.ShadowDirectionalLightExtrusionDistance;
// Round local x/y position based on a world-space texel; this helps to reduce
// jittering caused by the projection moving with the camera
// Viewport is 2 * near clip distance across (90 degree fov)
//~ Real worldTexelSize = (texCam->getNearClipDistance() * 20) / vp->getActualWidth();
//~ pos.x -= fmod(pos.x, worldTexelSize);
//~ pos.y -= fmod(pos.y, worldTexelSize);
//~ pos.z -= fmod(pos.z, worldTexelSize);
var worldTexelSize = ( shadowDist*2 )/textureCamera.Viewport.ActualWidth;
//get texCam orientation
var up = Vector3.UnitY;
// Check it's not coincident with dir
if ( Utility.Abs( up.Dot( dir ) ) >= 1.0f )
{
// Use camera up
up = Vector3.UnitZ;
}
// cross twice to rederive, only direction is unaltered
var left = dir.Cross( up );
left.Normalize();
up = dir.Cross( left );
up.Normalize();
// Derive quaternion from axes
q = Quaternion.FromAxes( left, up, dir );
//convert world space camera position into light space
var lightSpacePos = q.Inverse()*pos;
//snap to nearest texel
lightSpacePos.x -= lightSpacePos.x%worldTexelSize; //fmod(lightSpacePos.x, worldTexelSize);
lightSpacePos.y -= lightSpacePos.y%worldTexelSize; //fmod(lightSpacePos.y, worldTexelSize);
//convert back to world space
pos = q*lightSpacePos;
}
// Spotlight
else if ( light.Type == LightType.Spotlight )
{
// Set perspective projection
textureCamera.ProjectionType = Projection.Perspective;
// set FOV slightly larger than the spotlight range to ensure coverage
var fovy = light.SpotlightOuterAngle*1.2;
// limit angle
if ( fovy.InDegrees > 175 )
{
fovy = (Degree)( 175 );
}
textureCamera.FieldOfView = fovy;
// Calculate position, which same as spotlight position
pos = light.GetDerivedPosition();
// Calculate direction, which same as spotlight direction
dir = -light.DerivedDirection; // backwards since point down -z
dir.Normalize();
}
// Point light
else
{
// Set perspective projection
textureCamera.ProjectionType = Projection.Perspective;
// Use 120 degree FOV for point light to ensure coverage more area
textureCamera.FieldOfView = 120.0f;
// Calculate look at position
// We want to look at a spot shadowOffset away from near plane
// 0.5 is a litle too close for angles
var target = camera.DerivedPosition + ( camera.DerivedDirection*shadowOffset );
// Calculate position, which same as point light position
pos = light.GetDerivedPosition();
dir = ( pos - target ); // backwards since point down -z
dir.Normalize();
}
// Finally set position
textureCamera.Position = pos;
// Calculate orientation based on direction calculated above
/*
// Next section (camera oriented shadow map) abandoned
// Always point in the same direction, if we don't do this then
// we get 'shadow swimming' as camera rotates
// As it is, we get swimming on moving but this is less noticeable
// calculate up vector, we want it aligned with cam direction
Vector3 up = cam->getDerivedDirection();
// Check it's not coincident with dir
if (up.dotProduct(dir) >= 1.0f)
{
// Use camera up
up = cam->getUp();
}
*/
var up2 = Vector3.UnitY;
// Check it's not coincident with dir
if ( Utility.Abs( up2.Dot( dir ) ) >= 1.0f )
{
// Use camera up
up2 = Vector3.UnitZ;
}
// cross twice to rederive, only direction is unaltered
var left2 = dir.Cross( up2 );
left2.Normalize();
up2 = dir.Cross( left2 );
up2.Normalize();
// Derive quaternion from axes
q = Quaternion.FromAxes( left2, up2, dir );
textureCamera.Orientation = q;
}
