Function sam3_pe_encode_coord

sam3.cpp:10273–10286

Random Fourier positional encoding for a single (x, y) coordinate coords_norm: normalized to [0, 1], pe_gaussian: PyTorch row-major [2, 128] Output: [256] = [sin(128); cos(128)]

// coords_norm: normalized to [0, 1], pe_gaussian: PyTorch row-major [2, 128]
// Output: [256] = [sin(128); cos(128)]
static void sam3_pe_encode_coord(float* out, float x_norm, float y_norm,
                                 const float* pe_gauss, int num_pos_feats) {
    // Map [0,1] → [-1,1]
    float coords[2] = {2.0f * x_norm - 1.0f, 2.0f * y_norm - 1.0f};

    // coords @ pe_gaussian → [128]
    for (int i = 0; i < num_pos_feats; ++i) {
        float dot = coords[0] * pe_gauss[i] +
                    coords[1] * pe_gauss[num_pos_feats + i];
        dot *= 2.0f * (float)M_PI;
        out[i] = sinf(dot);
        out[i + num_pos_feats] = cosf(dot);
    }
}

// Read SAM prompt encoder weights from GPU and cache them in state.
// Also pre-computes the dense PE grid and no-mask tiled embedding.