private void DrawParallax(ArenaLayer layer)
{
if (layer.ParallaxName != "")
{
var oldState = GraphicsDevice.BlendState;
// Modify renderstate for parallax.
GraphicsDevice.SamplerStates[0] = SamplerState.LinearWrap;
GraphicsDevice.BlendState = BlendState.AlphaBlend;
GraphicsDevice.DepthStencilState = DepthStencilState.None;
// Render looping parallax as two huge triangles.
_effect.Texture = AssaultWingCore.Instance.Content.Load<Texture2D>(layer.ParallaxName);
var texCenter = GetScale(layer.Z) * CurrentLookAt / _effect.Texture.Dimensions();
var texCornerOffset = new Vector2(
Viewport.Width / (2f * _effect.Texture.Width) / ZoomRatio,
Viewport.Height / (2f * _effect.Texture.Height) / ZoomRatio);
_vertexData[0].TextureCoordinate = texCenter - texCornerOffset;
_vertexData[1].TextureCoordinate = texCenter + texCornerOffset.MirrorX();
_vertexData[2].TextureCoordinate = texCenter + texCornerOffset.MirrorY();
_vertexData[3].TextureCoordinate = texCenter + texCornerOffset;
_effect.CurrentTechnique.Passes[0].Apply();
GraphicsDevice.DrawUserPrimitives<VertexPositionTexture>(PrimitiveType.TriangleStrip, _vertexData, 0, 2);
}
// Modify renderstate for 3D graphics.
GraphicsDevice.SamplerStates[0] = SamplerState.LinearWrap;
GraphicsDevice.DepthStencilState = DepthStencilState.Default;
GraphicsDevice.BlendState = BlendState.Opaque;
}