1. A method for rendering an image of a fluid surface composed of a plurality of particles, the method comprising: (i) generating, by processor circuitry, a depth image of a plurality of particles forming a fluid surface, each particle i of the plurality of particles corresponding to a pixel of a plurality of pixels included in the depth image, wherein each particle is rendered as a screen-oriented quad; (ii) smoothing the depth image to generate a smoothed depth image; (iii) from the smoothed depth image, determining a smoothed surface position and a smoothed surface normal for each of the plurality of pixels included within the smoothed depth image; and (iv) rendering a shaded surface of the fluid as a function of the smoothed surface positions and the smoothed surface normals, wherein a fluid thickness value (T) for each pixel is computed according to the equation: T ⁡ ( x , y ) = ∑ i = 0 n ⁢ d ⁡ ( x - x i σ i , y - y i σ i ) where d is a kernel function d(x,y)=√{square root over (1−x 2 −y 2 )} in which x and y vary between −1 and +1 over a two dimensional screen space position of the particle and (x,y) is a particle position, n is the number of particles the computation is summed over, where x i and y i defines the projected position of the particle, and where σ i is a projected size of the particle.