1 reply to this topic

[Telanor]

I'm trying to calculate a view/projection/bounding frustum for the 6 directions of a point light and I'm having trouble with the views pointing along the Y axis. Our game uses a right-handed, Y-up system. For the other 4 directions I create the LookAt matrix using (0, 1, 0) as the up vector. Obviously that doesn't work when looking along the Y axis so for those I use an up vector of (-1, 0, 0) for -Y and (1, 0, 0) for +Y. The view matrix seems to come out correctly (and the projection matrix always stays the same), but the bounding frustum is definitely wrong.

This is the code I'm using:

camera.Projection = Matrix.PerspectiveFovRH((float)Math.PI / 2, ShadowMapSize / (float)ShadowMapSize, 1, 5);

for(var i = 0; i < 6; i++)
{
	var renderTargetView = shadowMap.GetRenderTargetView((TextureCubeFace)i);
	var up = DetermineLightUp((TextureCubeFace) i);
	var forward = DirectionToVector((TextureCubeFace) i);

	camera.View = Matrix.LookAtRH(Position, Position + forward, up);
	camera.BoundingFrustum = new BoundingFrustum(camera.View * camera.Projection);
}

private static Vector3 DirectionToVector(TextureCubeFace direction)
{
	switch (direction)
	{
		case TextureCubeFace.NegativeX:
			return -Vector3.UnitX;
		case TextureCubeFace.NegativeY:
			return -Vector3.UnitY;
		case TextureCubeFace.NegativeZ:
			return -Vector3.UnitZ;
		case TextureCubeFace.PositiveX:
			return Vector3.UnitX;
		case TextureCubeFace.PositiveY:
			return Vector3.UnitY;
		case TextureCubeFace.PositiveZ:
			return Vector3.UnitZ;
		default:
			throw new ArgumentOutOfRangeException("direction");
	}
}

private static Vector3 DetermineLightUp(TextureCubeFace direction)
{
	switch (direction)
	{
		case TextureCubeFace.NegativeY:
			return -Vector3.UnitX;
		case TextureCubeFace.PositiveY:
			return Vector3.UnitX;
		default:
			return Vector3.UnitY;
	}
}

I can post some example output if it'll help.

Edited by Telanor, 09 March 2013 - 10:51 PM.

[riuthamus]

If this is too technical let us know. I can provide you with a more basic understanding. Curious if anybody had any thoughts on this as it would help us deal with our point light issue. I can provide pictures/video!

Edited by riuthamus, 17 March 2013 - 03:51 AM.