1. A computer-implemented method for modeling ambient occlusion, the method comprising: receiving a first pixel location associated with a first depth value stored in a depth buffer; determining a volume, wherein the volume comprises a sphere centered at the first pixel location; determining depth values stored in the depth buffer for one or more pixel locations within a screen-space projection of the volume; applying a weight value based on a density function to the depth values for one or more pixel locations based on their distance from the first pixel location; calculating a distance using the depth values between each of the one or more pixel locations on the screen space projection and a boundary of the volume centered at the first pixel location; calculating an integral value of the distances between depth values at each of the one or more pixel locations and the volume centered at the first pixel location; adjusting a pixel value at the first pixel location based on the integral value; and displaying on a display device or storing in a memory a pixel that is associated with the first pixel location and is based on the pixel value.