{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/shadows-don-t-lie-and-lines-can-t-bend","title":"Shadows Don't Lie and Lines Can't Bend! Generative Models don't know Projective Geometry...for now","arxiv_id":"2311.17138","date":"2023-11-28","proceeding":"CVPR 2024 1","authors":["Ayush Sarkar","Hanlin Mai","Amitabh Mahapatra","Svetlana Lazebnik","D. A. Forsyth","Anand Bhattad"],"abstract":"Generative models can produce impressively realistic images. This paper demonstrates that generated images have geometric features different from those of real images. We build a set of collections of generated images, prequalified to fool simple, signal-based classifiers into believing they are real. We then show that prequalified generated images can be identified reliably by classifiers that only look at geometric properties. We use three such classifiers. All three classifiers are denied access to image pixels, and look only at derived geometric features. The first classifier looks at the perspective field of the image, the second looks at lines detected in the image, and the third looks at relations between detected objects and shadows. Our procedure detects generated images more reliably than SOTA local signal based detectors, for images from a number of distinct generators. Saliency maps suggest that the classifiers can identify geometric problems reliably. We conclude that current generators cannot reliably reproduce geometric properties of real images.","url_abs":"https://arxiv.org/abs/2311.17138v2","url_pdf":"https://arxiv.org/pdf/2311.17138v2.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"abstracts"},"code_links":[{"paper_slug":"shadows-don-t-lie-and-lines-can-t-bend","repo_url":"https://github.com/hanlinm2/projective-geometry","is_official":1,"mentioned_in_paper":0,"mentioned_in_github":1,"framework":"pytorch","reach":{"status":"ok","spdx":"MIT"}}],"tasks":[],"methods":[{"method_slug":"set","method_name":"SET"}],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":"https://syntology.ai/paper/2311.17138","atlas_url":"https://app.syntology.ai/?focus=2311.17138","mcp":{"get_harvested_code_for_paper":{"arxiv_id":"2311.17138"}},"developers":"https://syntology.ai/developers","read_at":"2026-09-25T09:33:49+00:00","read_at_is":"when the build read Syntology's graph, not when any sample ran","claim":"Per-sample execution status on synthesized fixtures; not a correctness claim about the paper. Samples come from repositories linked to the paper, official or community; repo_kind says which.","repos":[{"provenance":"external:paperswithcode_snapshot_2025-07-28","url":"https://github.com/hanlinm2/projective-geometry","reach":{"status":"ok","spdx":"MIT"}}],"summary":{"ran":17,"unverified":1},"by_repo_kind":{"official":{"samples":18,"ran":17,"repositories":1}},"repo_kind_vocabulary":{"official":"The archive marks this repository official for the paper","named_in_paper":"The archive records that the paper mentions this repository; it is not marked official","listed":"In the archive's code links for this paper, not marked official and not recorded as mentioned in the paper","found_in_text":"Syntology found this repository in the paper's own text; whether it is the authors' implementation is not asserted","community":"Not in the archive's code links for this paper; a community repository Syntology harvested"},"n_pointer_only_for_licence":0,"samples":[{"code_sha256_prefix":"a026c2d9978681cf","entry":"compute_roc_curve","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"prequalifier/prequalifier_test_helpers.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/prequalifier/prequalifier_test_helpers.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"a026c2d9978681cf"}},{"code_sha256_prefix":"a945396ca0b16803","entry":"create_model","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"line_segment/lines_model.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/line_segment/lines_model.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"a945396ca0b16803"}},{"code_sha256_prefix":"f3c36d02045cfbc2","entry":"create_model","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"perspective_fields/fields_model.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/perspective_fields/fields_model.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"f3c36d02045cfbc2"}},{"code_sha256_prefix":"949786004f8eb80c","entry":"evaluate_on_dataloader","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"prequalifier/prequalifier_test_helpers.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/prequalifier/prequalifier_test_helpers.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"949786004f8eb80c"}},{"code_sha256_prefix":"eb72ead7b49746e2","entry":"get_recent_timestamp_dataloaders","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"prequalifier/prequalifier_dataset.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/prequalifier/prequalifier_dataset.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"eb72ead7b49746e2"}},{"code_sha256_prefix":"7240b9840ca5e27e","entry":"get_test_dataloaders","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"line_segment/lines_dataset.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/line_segment/lines_dataset.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"7240b9840ca5e27e"}},{"code_sha256_prefix":"a52857a6650be07a","entry":"get_test_dataloaders","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"perspective_fields/fields_dataset.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/perspective_fields/fields_dataset.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"a52857a6650be07a"}},{"code_sha256_prefix":"627f7f54e5d786a4","entry":"get_test_dataloaders","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"prequalifier/prequalifier_dataset.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/prequalifier/prequalifier_dataset.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"627f7f54e5d786a4"}},{"code_sha256_prefix":"6e612f3f3508395b","entry":"get_train_dataloaders","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"line_segment/lines_dataset.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/line_segment/lines_dataset.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"6e612f3f3508395b"}},{"code_sha256_prefix":"59469a924d17ca67","entry":"get_train_dataloaders","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"perspective_fields/fields_dataset.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/perspective_fields/fields_dataset.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"59469a924d17ca67"}},{"code_sha256_prefix":"f6bbfd4b67f32c83","entry":"load_all_paths","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"line_segment/lines_path_helpers.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/line_segment/lines_path_helpers.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"f6bbfd4b67f32c83"}},{"code_sha256_prefix":"6b419f2ecfa7997a","entry":"load_model","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"line_segment/lines_model.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/line_segment/lines_model.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"6b419f2ecfa7997a"}},{"code_sha256_prefix":"bde9121fab9d6344","entry":"load_model","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"perspective_fields/fields_model.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/perspective_fields/fields_model.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"bde9121fab9d6344"}},{"code_sha256_prefix":"c56c6c235242c726","entry":"load_outdoor_problem_paths","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"line_segment/lines_path_helpers.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/line_segment/lines_path_helpers.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"c56c6c235242c726"}},{"code_sha256_prefix":"f372edd1805aaa57","entry":"load_recent_timestamp_paths","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"prequalifier/prequalifier_path_helpers.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/prequalifier/prequalifier_path_helpers.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"f372edd1805aaa57"}},{"code_sha256_prefix":"45dd68d819a5dbf6","entry":"remove_problem_paths","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"line_segment/lines_path_helpers.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/line_segment/lines_path_helpers.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"45dd68d819a5dbf6"}},{"code_sha256_prefix":"4ba2962f643eb701","entry":"timestamp_paths_from_data_paths","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"prequalifier/prequalifier_path_helpers.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/prequalifier/prequalifier_path_helpers.py","link_basis":"first_harvest_node","language":"python","status":"ran","verification_level":1,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"4ba2962f643eb701"}},{"code_sha256_prefix":"f9e6838b930e3168","entry":"load_model","repo":"hanlinm2/projective-geometry","repo_kind":"official","path":"prequalifier/prequalifier_model.py","file_url":"https://github.com/hanlinm2/projective-geometry/blob/HEAD/prequalifier/prequalifier_model.py","link_basis":"first_harvest_node","language":"python","status":"unverified","verification_level":0,"contract_check":null,"metamorphic_tier":null,"behaviour_fingerprint":false,"licence":"MIT","inline_ok":true,"mcp_get_code":{"code_sha256":"f9e6838b930e3168"}}]},"arxiv_metadata":null,"syntology_extracted_results":null}