gzdoom-gles/src/textures/warpbuffer.h

template<class TYPE> 
void WarpBufferType1(TYPE *Pixels, const TYPE *source, int width, int height, int xmul, int ymul, unsigned time, float Speed)
{
	TYPE *buffer = (TYPE *)alloca(sizeof(TYPE) * MAX(width, height));
	int ymask = height - 1;
	int x, y;

	// [mxd] Rewrote to fix animation for NPo2 textures
	unsigned timebase = unsigned(time * Speed * 32 / 28);
	for (y = height - 1; y >= 0; y--)
	{
		int xf = (TexMan.sintable[((timebase + y*ymul) >> 2)&TexMan.SINMASK] >> 11) % width;
		if (xf < 0) xf += width;
		int xt = xf;
		const TYPE *sourcep = source + y;
		TYPE *dest = Pixels + y;
		for (xt = width; xt; xt--, xf = (xf + 1) % width, dest += height)
			*dest = sourcep[xf + ymask * xf];
	}
	timebase = unsigned(time * Speed * 23 / 28);
	for (x = width - 1; x >= 0; x--)
	{
		int yf = (TexMan.sintable[((time + (x + 17)*xmul) >> 2)&TexMan.SINMASK] >> 11) % height;
		if (yf < 0) yf += height;
		int yt = yf;
		const TYPE *sourcep = Pixels + (x + ymask * x);
		TYPE *dest = buffer;
		for (yt = height; yt; yt--, yf = (yf + 1) % height)
			*dest++ = sourcep[yf];
		memcpy(Pixels + (x + ymask*x), buffer, height * sizeof(TYPE));
	}
}


template<class TYPE>
void WarpBufferType2(TYPE *Pixels, const TYPE *source, int width, int height, int xmul, int ymul, unsigned time, float Speed)
{
	int ymask = height - 1;
	int x, y;

	unsigned timebase = unsigned(time * Speed * 40 / 28);
	// [mxd] Rewrote to fix animation for NPo2 textures
	for (x = 0; x < width; x++)
	{
		TYPE *dest = Pixels + (x + ymask * x);
		for (y = 0; y < height; y++)
		{
			int xt = (x + 128
				+ ((TexMan.sintable[((y*ymul + timebase * 5 + 900) >> 2) & TexMan.SINMASK]) >> 13)
				+ ((TexMan.sintable[((x*xmul + timebase * 4 + 300) >> 2) & TexMan.SINMASK]) >> 13)) % width;

			int yt = (y + 128
				+ ((TexMan.sintable[((y*ymul + timebase * 3 + 700) >> 2) & TexMan.SINMASK]) >> 13)
				+ ((TexMan.sintable[((x*xmul + timebase * 4 + 1200) >> 2) & TexMan.SINMASK]) >> 13)) % height;

			*dest++ = source[(xt + ymask * xt) + yt];
		}
	}
}