out vec2 out_flow;
uniform sampler2D flow_tex, grad0_tex, image0_tex, image1_tex;
-uniform float image_width, image_height, inv_image_width, inv_image_height;
+uniform vec2 image_size, inv_image_size;
void main()
{
// Lock patch_bottom_left_texel to an integer, so that we never get
// any bilinear artifacts for the gradient.
- vec2 base = round(patch_bottom_left_texel * vec2(image_width, image_height))
- * vec2(inv_image_width, inv_image_height);
+ vec2 base = round(patch_bottom_left_texel * image_size)
+ * inv_image_size;
// First, precompute the pseudo-Hessian for the template patch.
// This is the part where we really save by the inverse search
mat2 H = mat2(0.0f);
for (uint y = 0; y < patch_size; ++y) {
for (uint x = 0; x < patch_size; ++x) {
- vec2 tc;
- tc.x = base.x + x * inv_image_width;
- tc.y = base.y + y * inv_image_height;
+ vec2 tc = base + uvec2(x, y) * inv_image_size;
vec2 grad = texture(grad0_tex, tc).xy;
H[0][0] += grad.x * grad.x;
H[1][1] += grad.y * grad.y;
mat2 H_inv = inverse(H);
- // Fetch the initial guess for the flow.
- vec2 initial_u = texture(flow_tex, flow_tc).xy;
+ // Fetch the initial guess for the flow. (We need the normalization step
+ // because densification works by accumulating; see the comments on the
+ // Densify class.)
+ vec3 prev_flow = texture(flow_tex, flow_tc).xyz;
+ vec2 initial_u;
+ if (prev_flow.z < 1e-3) {
+ initial_u = vec2(0.0, 0.0);
+ } else {
+ initial_u = prev_flow.xy / prev_flow.z;
+ }
+
+ // Note: The flow is in OpenGL coordinates [0..1], but the calculations
+ // generally come out in pixels since the gradient is in pixels,
+ // so we need to convert at the end.
vec2 u = initial_u;
for (uint i = 0; i < num_iterations; ++i) {
vec2 du = vec2(0.0, 0.0);
for (uint y = 0; y < patch_size; ++y) {
for (uint x = 0; x < patch_size; ++x) {
- vec2 tc;
- tc.x = base.x + x * inv_image_width;
- tc.y = base.y + y * inv_image_height;
+ vec2 tc = base + uvec2(x, y) * inv_image_size;
vec2 grad = texture(grad0_tex, tc).xy;
float t = texture(image0_tex, tc).x;
float warped = texture(image1_tex, tc + u).x;
du += grad * (warped - t);
}
}
- u += (H_inv * du) * vec2(inv_image_width, inv_image_height);
+ u += (H_inv * du) * inv_image_size;
}
// Reject if we moved too far.
- if (length((u - initial_u) * vec2(image_width, image_height)) > patch_size) {
+ if (length((u - initial_u) * image_size) > patch_size) {
u = initial_u;
}