I’m trying to make a simple 2D platformer in XNA, but I’m having trouble with the vertical scrolling.
What I’m trying to accomplish is that whenever the player is above half the height of the screen, the player should jump and fall. However, if the player is below half the height of the screen, then the player should remain in the middle of the screen and the background image and platforms should move around him instead, creating a scrolling effect.
I’m not sure why, but whenever the player is at half the height of the screen, the background and platforms don’t move as much as they should, so the player can’t make jumps that he would otherwise be able to.
I’m at a loss as to how to fix this issue, can anyone help? Any assistance would be much appreciated.
if (keyState.IsKeyDown(Keys.D)) { if (player.position.X < bgView.Width / 2 || bgView.X >= backgroundImage.Width - bgView.Width) //If the player position is less than 400px or if the bgView is greater than 1200 then the player moves, the BG is stationary { player.position.X += speed; } else //If the player is greater than 400px and and the bgView is less than 1200 then the BG elements move instead, the player remains centred { bgView.X += 4; //moves the BG for (int i = 0; i < rows; i++) { for (int j = 0; j < cols; j++) { if (block[i, j].position.X < bgView.Width / 2 || bgView.X >= backgroundImage.Width - bgView.Width) { block[i, j].position.X -= speed; //moves the platforms } else { block[i, j].position.X -= speed; } } } } } if (keyState.IsKeyDown(Keys.A)) { if (player.position.X > bgView.Width / 2 || bgView.X <= 0) { player.position.X -= speed; } else { bgView.X -= 4; for (int i = 0; i < rows; i++) { for (int j = 0; j < cols; j++) { block[i, j].position.X += speed; } } } } if (player.position.X < 0) //Stops the player from moving backwards from the beginning of the stage { player.position.X = 0; } if (player.position.Y + player.image.Height > screenHeight) //Stops the player from falling through the floor { player.position.Y = screenHeight - (player.rectangle.Height); } if (player.position.X + player.image.Width > screenWidth) //Stops the player from leaving the end of the stage { player.position.X = screenWidth - player.image.Width; } for (int i = 0; i < rows; i++) //Checks the player position to see if it's intersecting a block's rectangle. { for (int j = 0; j < cols; j++) { if (player.position.Y + player.image.Height >= block[i, j].rectangle.Top - 1 && //checks if the player is intersecting the top of a block player.position.Y + player.image.Height <= block[i, j].rectangle.Top + (block[i, j].rectangle.Height / 2) && player.position.X + player.image.Width >= block[i, j].rectangle.Left + (block[i, j].rectangle.Width / 5) && player.position.X <= block[i, j].rectangle.Right - block[i, j].rectangle.Width / 5) { gravity = 0; jumping = false; player.position = new Vector2(player.position.X, (block[i, j].position.Y + 1) - player.image.Height); touchingTop = true; } if (player.position.Y <= block[i, j].rectangle.Bottom + (block[i, j].rectangle.Height / 5) && //checks if the player is intersecting the bottom of a block player.position.Y >= block[i, j].rectangle.Bottom - 1 && player.position.X + player.image.Width >= block[i, j].rectangle.Left + (block[i, j].rectangle.Width / 5) && player.position.X <= block[i, j].rectangle.Right - (block[i, j].rectangle.Width / 2)) { player.position = new Vector2(player.position.X, block[i, j].rectangle.Bottom + 5); force = 0; } if (player.position.X + player.image.Width <= block[i, j].rectangle.Right && //checks if the player is intersecting the left of a block player.position.X + player.image.Width >= block[i, j].rectangle.Left - 5 && player.position.Y <= block[i, j].rectangle.Bottom - (block[i, j].rectangle.Width / 4) && player.position.Y + player.image.Height >= block[i, j].rectangle.Top + (block[i, j].rectangle.Width / 4)) { player.position = new Vector2(player.position.X - 4, player.position.Y); } if (player.position.X >= block[i, j].rectangle.Left && //checks if the player is intersecting the right of a block player.position.X <= block[i, j].rectangle.Right + 5 && player.position.Y <= block[i, j].rectangle.Bottom - (block[i, j].rectangle.Width / 4) && player.position.Y + player.image.Height >= block[i, j].rectangle.Top + (block[i, j].rectangle.Width / 4)) { player.position = new Vector2(player.position.X + 4, player.position.Y); } } } for (int i = 0; i < rows; i++) //sets the block's rectangle position { for (int j = 0; j < cols; j++) { block[i, j].rectangle.X = (int)block[i, j].position.X; block[i, j].rectangle.Y = (int)block[i, j].position.Y; } } //Checks whether or not the player is falling if (force <= 7) { falling = true; } if (force > 7) { falling = false; } if (keyState.IsKeyDown(Keys.W)) //After the player jumps, the force of the jump decreases over time, increasing the speed of falling { jumping = true; } if (jumping && player.position.Y + (player.image.Height / 2) > screenHeight / 2) { touchingTop = false; player.position.Y -= force; force -= 0.3f; if (force < 0) { force = 0; } } if (player.position.Y + (player.image.Height / 2) <= screenHeight / 2) { player.position.Y = screenHeight / 2 - (player.image.Height / 2); bgView.Y -= (int)force; bgView.Y += (int)gravity; for (int i = 0; i < rows; i++) { for (int j = 0; j < cols; j++) { block[i, j].position.Y += (int)force; } } } else { bgView.Y += (int)force; } for (int i = 0; i < rows; i++) //Stops the blocks from ascending higher than the position they start at { for (int j = 0; j < cols; j++) { block[i, j].position.Y -= gravity; if (block[i, j].position.Y <= block[i,j].startingPos.Y) { block[i, j].position.Y = block[i,j].startingPos.Y; } } } if (!jumping) { force = 14f; } if (bgView.X < 0) //Prevents the background from scrolling backwards from the beginning of the stage { bgView.X = 0; } if (bgView.Y > 600) { bgView.Y = 600; } if (bgView.Y < 0) { bgView.Y = 0; } player.position.Y += gravity; //Gravity is constantly being added to the player's Y position base.Update(gameTime); } 
