Add support for saving lightmap as multiple images

[techiepriyansh]

master port of #58102.

Needs to be tested on a really large scene for the "roll-over to multiple textures" limit to be reached. I have only tested by hardcoding slices_per_texture = 1, but in theory, should work just fine for the general case too.

Also, currently there is lightmap texture data duplication as both the individual textures and the combined texture co-exist. Need to figure out a way around it. (This only happens when the texture data cannot be contained in a single Image; so no overhead until the roll-over limit is reached). ✅

[Calinou]

I tested this PR on #54679 and it doesn't fix the crash encountered when baking lightmaps, even after setting the maximum texture size to 8192. I suppose this doesn't work on that MRP since it only uses a single large mesh, as opposed to several smaller meshes.

That said, the original crash may be better fixed by using int64_t where it's relevant in Image.

[techiepriyansh]

Can you please attach the backtrace of the crash?

[Calinou]

Can you please attach the backtrace of the crash?

It's slightly different from the one listed in #54679, but I had a similar backtrace with a master build from today.

================================================================
handle_crash: Program crashed with signal 4
Engine version: Godot Engine v4.0.alpha.custom_build (17a7447dbe502ad7b8ea672ae59f320a9a991e35)
Dumping the backtrace. Please include this when reporting the bug on https://github.com/godotengine/godot/issues
[1] /lib64/libc.so.6(+0x42a70) [0x7fa849ee2a70] (??:0)
[2] CowData<Ref<Image> >::get(int) const (/home/hugo/Documents/Git/godotengine/godot/./core/templates/cowdata.h:156)
[3] Vector<Ref<Image> >::operator[](int) const (/home/hugo/Documents/Git/godotengine/godot/./core/templates/vector.h:92)
[4] LightmapGI::bake(Node*, String, bool (*)(float, String const&, void*, bool), void*) (/home/hugo/Documents/Git/godotengine/godot/scene/3d/lightmap_gi.cpp:1014)
[5] LightmapGIEditorPlugin::_bake_select_file(String const&) (/home/hugo/Documents/Git/godotengine/godot/editor/plugins/lightmap_gi_editor_plugin.cpp:43)
[6] void call_with_variant_args_helper<LightmapGIEditorPlugin, String const&, 0ul>(LightmapGIEditorPlugin*, void (LightmapGIEditorPlugin::*)(String const&), Variant const**, Callable::CallError&, IndexSequence<0ul>) (/home/hugo/Documents/Git/godotengine/godot/./core/variant/binder_common.h:236)
[7] void call_with_variant_args<LightmapGIEditorPlugin, String const&>(LightmapGIEditorPlugin*, void (LightmapGIEditorPlugin::*)(String const&), Variant const**, int, Callable::CallError&) (/home/hugo/Documents/Git/godotengine/godot/./core/variant/binder_common.h:351)
[8] CallableCustomMethodPointer<LightmapGIEditorPlugin, String const&>::call(Variant const**, int, Variant&, Callable::CallError&) const (/home/hugo/Documents/Git/godotengine/godot/./core/object/callable_method_pointer.h:105)
[9] Callable::call(Variant const**, int, Variant&, Callable::CallError&) const (/home/hugo/Documents/Git/godotengine/godot/core/variant/callable.cpp:51)
[10] Object::emit_signalp(StringName const&, Variant const**, int) (/home/hugo/Documents/Git/godotengine/godot/core/object/object.cpp:1119)
[11] Error Object::emit_signal<String>(StringName const&, String) (/home/hugo/Documents/Git/godotengine/godot/./core/object/object.h:773)
[12] EditorFileDialog::_action_pressed() (/home/hugo/Documents/Git/godotengine/godot/editor/editor_file_dialog.cpp:487)
[13] EditorFileDialog::_file_submitted(String const&) (/home/hugo/Documents/Git/godotengine/godot/editor/editor_file_dialog.cpp:251)
[14] void call_with_variant_args_helper<EditorFileDialog, String const&, 0ul>(EditorFileDialog*, void (EditorFileDialog::*)(String const&), Variant const**, Callable::CallError&, IndexSequence<0ul>) (/home/hugo/Documents/Git/godotengine/godot/./core/variant/binder_common.h:236)
[15] void call_with_variant_args<EditorFileDialog, String const&>(EditorFileDialog*, void (EditorFileDialog::*)(String const&), Variant const**, int, Callable::CallError&) (/home/hugo/Documents/Git/godotengine/godot/./core/variant/binder_common.h:351)
[16] CallableCustomMethodPointer<EditorFileDialog, String const&>::call(Variant const**, int, Variant&, Callable::CallError&) const (/home/hugo/Documents/Git/godotengine/godot/./core/object/callable_method_pointer.h:105)
[17] Callable::call(Variant const**, int, Variant&, Callable::CallError&) const (/home/hugo/Documents/Git/godotengine/godot/core/variant/callable.cpp:51)
[18] Object::emit_signalp(StringName const&, Variant const**, int) (/home/hugo/Documents/Git/godotengine/godot/core/object/object.cpp:1119)
[19] Error Object::emit_signal<String>(StringName const&, String) (/home/hugo/Documents/Git/godotengine/godot/./core/object/object.h:773)
[20] LineEdit::gui_input(Ref<InputEvent> const&) (/home/hugo/Documents/Git/godotengine/godot/scene/gui/line_edit.cpp:461)
[21] Control::_call_gui_input(Ref<InputEvent> const&) (/home/hugo/Documents/Git/godotengine/godot/scene/gui/control.cpp:940)
[22] Viewport::_gui_input_event(Ref<InputEvent>) (/home/hugo/Documents/Git/godotengine/godot/scene/main/viewport.cpp:1995)
[23] Viewport::push_input(Ref<InputEvent> const&, bool) (/home/hugo/Documents/Git/godotengine/godot/scene/main/viewport.cpp:2741)
[24] Window::_window_input(Ref<InputEvent> const&) (/home/hugo/Documents/Git/godotengine/godot/scene/main/window.cpp:973)
[25] void call_with_variant_args_helper<Window, Ref<InputEvent> const&, 0ul>(Window*, void (Window::*)(Ref<InputEvent> const&), Variant const**, Callable::CallError&, IndexSequence<0ul>) (/home/hugo/Documents/Git/godotengine/godot/./core/variant/binder_common.h:236)
[26] void call_with_variant_args<Window, Ref<InputEvent> const&>(Window*, void (Window::*)(Ref<InputEvent> const&), Variant const**, int, Callable::CallError&) (/home/hugo/Documents/Git/godotengine/godot/./core/variant/binder_common.h:351)
[27] CallableCustomMethodPointer<Window, Ref<InputEvent> const&>::call(Variant const**, int, Variant&, Callable::CallError&) const (/home/hugo/Documents/Git/godotengine/godot/./core/object/callable_method_pointer.h:105)
[28] Callable::call(Variant const**, int, Variant&, Callable::CallError&) const (/home/hugo/Documents/Git/godotengine/godot/core/variant/callable.cpp:51)
[29] DisplayServerX11::_dispatch_input_event(Ref<InputEvent> const&) (/home/hugo/Documents/Git/godotengine/godot/platform/linuxbsd/display_server_x11.cpp:3136)
[30] DisplayServerX11::_dispatch_input_events(Ref<InputEvent> const&) (/home/hugo/Documents/Git/godotengine/godot/platform/linuxbsd/display_server_x11.cpp:3108)
[31] Input::_parse_input_event_impl(Ref<InputEvent> const&, bool) (/home/hugo/Documents/Git/godotengine/godot/core/input/input.cpp:662)
[32] Input::flush_buffered_events() (/home/hugo/Documents/Git/godotengine/godot/core/input/input.cpp:887)
[33] DisplayServerX11::process_events() (/home/hugo/Documents/Git/godotengine/godot/platform/linuxbsd/display_server_x11.cpp:4117)
[34] OS_LinuxBSD::run() (/home/hugo/Documents/Git/godotengine/godot/platform/linuxbsd/os_linuxbsd.cpp:437)
[35] bin/godot.linuxbsd.tools.64.llvm(main+0x1c0) [0x4277fb0] (/home/hugo/Documents/Git/godotengine/godot/platform/linuxbsd/godot_linuxbsd.cpp:68)
[36] /lib64/libc.so.6(+0x2d590) [0x7fa849ecd590] (??:0)
[37] /lib64/libc.so.6(__libc_start_main+0x89) [0x7fa849ecd649] (??:0)
[38] bin/godot.linuxbsd.tools.64.llvm(_start+0x25) [0x4277d25] (??:?)
-- END OF BACKTRACE --
================================================================
[1]    21845 IOT instruction (core dumped)  bin/godot.linuxbsd.tools.64.llvm ~/Downloads/global_illumination/project.godo

[mrjustaguy]

This would close godotengine/godot-proposals#3734

[JFonS]

Looks great, really clean implementation. I did some testing and everything is working as expected.

[akien-mga]

Thanks!