map coordinates?
February 22, 2000 05:02 PM
I''ve just got scrolling to work and Im trying to figure out how to incorporate a map coordinate system. Like lets say you have a gun''s image being emited from the player and you want that image to be moved around the screen by the maps/world''s coordinates. If you move it by the screen''s coordinates then what happens is when you move, it moves with you instead of moving off the screen in one direction. Does anyone know of a good way to of doing this?
Thanx,
ViPeR
122
February 22, 2000 05:23 PM
I think this is the third time I write this anwer here. 
Keep all entities in Map coordinates. When drawing you compute the views top left corner''s map coordinates and then draw the entities on the screen at position = UnitPos - ViewPos.
Keep all entities in Map coordinates. When drawing you compute the views top left corner''s map coordinates and then draw the entities on the screen at position = UnitPos - ViewPos.
122
February 24, 2000 04:15 PM
But, can you explain the formula that you have put down? I don''t quite understand how it works.
122
February 24, 2000 04:28 PM
I''ll give it a try...
All entities positions are given in map coordinates, including the camera/view position.
The algoritm for rendering the map:
I hope that helps
All entities positions are given in map coordinates, including the camera/view position.
The algoritm for rendering the map:
- Figure out the view''s top left map coordinates. Let''s call this V.
V is calculated by taking the cameras position and subtracting half of the width and height. - Render the background to the screen. This is done by blitting from the map a rectangle going from V to (V.x + Width, V.y + Height).
- For every entity in the world.
- Compute the entities screen coordinates. Let''s call this E.
You do this by taking the entities map coordinates and subtracting V. - Check if E is within the screen. If its not it shouldn''t be rendered.
- Render the entity by blitting its surface to the screen with destination rectangle (E.x, E.y, E.x+Entity width, E.y+Entity height)
- Compute the entities screen coordinates. Let''s call this E.
- Move all entities according to their logic.
- Start over from the beginning.
I hope that helps
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