在时间T，位置x，y处的多边形

Question

I am trying to make polygon A be at position (x,y) at time= 1 sec for example. Then it should be at position (x,y+2) when time = 2 sec. Then I plan to make more polygons like this. I also want this to be animated and the polygon to smoothly move from the first position to the second, not a polygon jumping a round.

Now thus far, I have learned about the glutTimerFunction, however, from my understanding, I cannot individually tell polygons to be at position (x,y) and time T. But rather it seems like I have to make every polygon that i desire(around 500) and then have timer cycle through all the polygons at once.

Is there a way to explicitly tell the polygon to be at position (x,y) at time T using the glutTimerFunc?

Answer 1

OpenGL is a low level API, not an engine or a framework. It has no built-in method for automatically doing interpolation between positions over time, that's up to you as the engine writer to implement as you see fit. Linear interpolation between two points over time is fairly easy (ie, in pseudocode position = startPos + ((endPos - startPos) * timeElapsed ). Interpolation along a more complex curve is essentially the same, just the math is a little more involved to represent the desired curve.

You are correct that you must iterate through all of your polygons by hand and position them. This is another feature of using the low level graphics API instead of a pre-written engine.

There are a number of engines of varying complexity (and price) available that abstract away these details for you, however, if your goal is to learn graphics programming I would suggest shying away from them and plowing through.