uniform sampler2DArray flow_tex, image_tex;
uniform usampler2DArray grad_tex; // Also contains the corresponding reference image.
uniform vec2 inv_image_size, inv_prev_level_size;
uniform sampler2DArray flow_tex, image_tex;
uniform usampler2DArray grad_tex; // Also contains the corresponding reference image.
uniform vec2 inv_image_size, inv_prev_level_size;