Draw curved custom object in LIBGDX?

问题:

I've recently been looking into LibGDX and seem to have hit a wall, seen in the picture, the blue dot represents the users finger, the map generation it self is where i seem to get stuck, does LibGDX provide a method of dynamically drawing curved objects? I could simply generate them myself as images but then the image is hugely stretched to the point of the gap for the finger can fit 3! But also would need to be 1000's of PX tall to accommodate the whole level design.

Is it such that i should be drawing hundreds of polygons close together to make a curved line? On a side not i'll need a way of determining when the object has from bottom to top so i can generate another 'chunk' of map.

回答1:

You don't need hundreds of polygons to make a curve like you drew. You could get away with 40 quads on the left, and 40 on the right, and it would look pretty smooth. Raise that to 100 on each side and it will look almost perfectly smooth, and no modern device is going to have any trouble running that at 60fps.

You could use the Mesh class to generate a procedural mesh for each side. You can make the mesh stay in one spot, locked to the camera, and modify it's vertices and UVs to make it look like you are panning down an infinitely long corridor. This will take a fair amount of math up front but should be smooth sailing once you have that down.

Basically, your level design could be based on some kind of equation that takes Y offset as an input. Or it could be a long array of offsets, and you could use a spline equation or linear equation to interpolate between them. The output would be the UV and X coordinates which can be used to update each of the vertices of your two meshes.

You can use the vertex shader to efficiently update the UV coordinates, using a constant offset uniform parameter that you update each frame. That way you don't have to move UV data to the GPU every frame.

For the vertex positions, use your Mesh's underlying float[] and call setVertices() each frame to update it. Info here.

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Actually, it might look better if you leave the UV's and the X positions alone, and just scroll the Y positions up. Keep a couple quads of padding off top and bottom of screen, and just move the top quad to the bottom after it scrolls off screen.

回答2:

How about creating a set of curved forms that can be put together variably. Like the gap in the middle will at the top and bottom of each image be in the middle (with the same curvature at end and beginning points)... And inbetween the start and end points you can go crazy on the shape.

And finally, you can randomly put those images together and get an endless world.

If you don't want to stop in the middle each time, you could also have like three entry and exit points (left, middle, right)... and after an image that ends left, you of course need to add an image that starts left, but might end somewhere else...