Sign in to follow this  
Followers 0

Vertical parallax scrolling

1 post in this topic

i have set up a simple 2D game with the help of the Platformer Starter-Kit for XNA. I have reworked the CameraCode (to have it in a own class with a transformation matrix). Now i want to have vertical parallax scrolling (it works fine horizontally) but i cannot get it to work vertically.
Here is how it is set up:


 private void ScrollCamera(Viewport viewport)
                const float ViewMargin = 0.35f;
                // Calculate the edges of the screen.
                float marginHeight = viewport.Height * ViewMargin;
                float marginTop = cameraPositionY + marginHeight;
                float marginBottom = cameraPositionY + viewport.Height - marginHeight;
                float marginWidth = viewport.Width * ViewMargin;
                float marginLeft = cameraPositionX + marginWidth;
                float marginRight = cameraPositionX + viewport.Width - marginWidth;
                // Calculate how far to scroll when the player is near the edges of the screen.
                float cameraMovementX = 0.0f;
                if (Player.Position.X < marginLeft)
                    cameraMovementX = Player.Position.X - marginLeft;
                else if (Player.Position.X > marginRight)
                    cameraMovementX = Player.Position.X - marginRight;
                float cameraMovementY = 0.0f;
                if (Player.Position.Y < marginTop)
                    cameraMovementY = Player.Position.Y - marginTop;
                else if (Player.Position.Y > marginBottom)
                    cameraMovementY = Player.Position.Y - marginBottom;
                // Update the camera position, but prevent scrolling off the ends of the level.
                float maxCameraPositionY = Tile.Height * Height - viewport.Height;
                float maxCameraPositionX = Tile.Width * Width - viewport.Width;
                cameraPositionX = MathHelper.Clamp(cameraPositionX + cameraMovementX, 0.0f, maxCameraPositionX);
                cameraPositionY = MathHelper.Clamp(cameraPositionY + cameraMovementY, 0.0f, maxCameraPositionY);


This function calculates the current position of the camera. 
 - "Height" = tiles.GetLength(1) where "tiles" is a 2D Array and 
 - "Width" = tiles.GetLength(0). So my world is represented in this 2D array
 - Tile.Height and Tile.Width are the dimensions of my Tiles (i am currently working with tiles of the same size)
Now i am using this draw-call:


                for (int i = 0; i <= EntityLayer; ++i)
                    layers[i].Draw(spriteBatch, camera._pos, i);
                camera._pos = new Vector2(cameraPositionX, cameraPositionY);
                spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.PointClamp, DepthStencilState.Default, RasterizerState.CullNone, null, camera.get_transformation(spriteBatch.GraphicsDevice));
                Player.Draw(gameTime, spriteBatch);
                for (int i = EntityLayer + 1; i < layers.Length; ++i)
                    layers[i].Draw(spriteBatch, camera._pos, i);


I want to control the drawing process of the brackground layer seperately, like so:


 public void Draw(SpriteBatch spriteBatch, Vector2 cameraPosition, int index)
                int segmentWidth = Textures[index].Width;
                int segmentHeight = Textures[index].Height;
                // Calculate which segments to draw and how much to offset them.
                float x = cameraPosition.X * ScrollRate;
                int leftSegment = (int)Math.Floor(x / segmentWidth);
                int rightSegment = leftSegment + 1;
                x = (x / segmentWidth - leftSegment) * -segmentWidth;
                float y = cameraPosition.Y * ScrollRate;
                int topSegment = (int)Math.Floor(y / segmentHeight);
                y = (y / segmentHeight - topSegment) * -segmentHeight;
                spriteBatch.Draw(Textures[leftSegment % Textures.Length], new Vector2(x, y + 136f), Color.White);
                spriteBatch.Draw(Textures[rightSegment % Textures.Length], new Vector2(x + segmentWidth, y + 136f), Color.White);


Now i am pretty sure that there is problem with my calculation of my "y" but i cannot see it. Maybe someone can give me a hint or just a better way to approach this problem. Thanks a lot!
EDIT: Forgot to mention that it works fine for the tiles.
EDIT2: Sorry forgot to explain further: The Background Layers are scrolling nice horizontally but aren't aligned to the ground. They have an offset in the y-direction wich gets bigger and bigger depending on the total height of the level. I hope this clears some questions. If you still have some please let me know (i can also provide a screenshot if necessary) Thanks a lot

Share this post

Link to post
Share on other sites

Maybe someone could explain how he has done it? I am not sure how to approach this problem, so my "solution" could be very wrong.


Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  
Followers 0