public static void SimpleShadowmapProjection(
List <SSObject> objects,
SSLight light,
FrustumCuller frustum, // can be null (disabled)
SSCamera camera,
out float width, out float height, out float nearZ, out float farZ,
out Vector3 viewEye, out Vector3 viewTarget, out Vector3 viewUp)
{
if (light.Type != SSLight.LightType.Directional)
{
throw new NotSupportedException();
}
// light-aligned unit vectors
Vector3 lightZ = light.Direction.Normalized();
Vector3 lightX, lightY;
OpenTKHelper.TwoPerpAxes(lightZ, out lightX, out lightY);
// Step 1: light-direction aligned AABB of the visible objects
Vector3 projBBMin = new Vector3(float.PositiveInfinity);
Vector3 projBBMax = new Vector3(float.NegativeInfinity);
foreach (var obj in objects)
{
if (obj.renderState.toBeDeleted ||
!obj.renderState.visible ||
!obj.renderState.castsShadow)
{
continue;
}
else if (frustum == null || (obj.boundingSphere != null &&
frustum.isSphereInsideFrustum(obj.Pos, obj.ScaledRadius)))
{
// determine AABB in light coordinates of the objects so far
Vector3 lightAlignedPos = OpenTKHelper.ProjectCoord(obj.Pos, lightX, lightY, lightZ);
Vector3 rad = new Vector3(obj.ScaledRadius);
Vector3 localMin = lightAlignedPos - rad;
Vector3 localMax = lightAlignedPos + rad;
projBBMin = Vector3.ComponentMin(projBBMin, localMin);
projBBMax = Vector3.ComponentMax(projBBMax, localMax);
}
}
if (frustum != null)
{
// then we need to do a second pass, including shadow-casters that
// are between the camera-frusum and the light
// compute the camera's position in lightspace, because we need to
// include everything "closer" that the midline of the camera frustum
Vector3 lightAlignedCameraPos = OpenTKHelper.ProjectCoord(camera.Pos, lightX, lightY, lightZ);
float minZTest = lightAlignedCameraPos.Z;
// TODO what happens if all objects are exluded?
// Step 2: Extend Z of AABB to cover objects "between" current AABB and the light
foreach (var obj in objects)
{
if (obj.renderState.toBeDeleted ||
!obj.renderState.visible ||
!obj.renderState.castsShadow)
{
continue;
}
Vector3 lightAlignedPos = OpenTKHelper.ProjectCoord(obj.Pos, lightX, lightY, lightZ);
Vector3 rad = new Vector3(obj.ScaledRadius);
Vector3 localMin = lightAlignedPos - rad;
Vector3 localMax = lightAlignedPos + rad;
if (OpenTKHelper.RectsOverlap(projBBMin.Xy, projBBMax.Xy, localMin.Xy, localMax.Xy) &&
localMin.Z < minZTest)
{
projBBMin = Vector3.ComponentMin(projBBMin, localMin);
projBBMax = Vector3.ComponentMax(projBBMax, localMax);
}
}
}
// Finish the projection matrix
// Use center of AABB in regular coordinates to get the view matrix
Vector3 centerAligned = (projBBMin + projBBMax) / 2f;
viewTarget = centerAligned.X * lightX
+ centerAligned.Y * lightY
+ centerAligned.Z * lightZ;
float farEnough = (centerAligned.Z - projBBMin.Z) + 1f;
viewEye = viewTarget - farEnough * lightZ;
viewUp = lightY;
width = projBBMax.X - projBBMin.X;
height = projBBMax.Y - projBBMin.Y;
nearZ = 1f;
farZ = 1f + (projBBMax.Z - projBBMin.Z);
}