Vulkan: PointLight2D shadows only partially appear

[kezzbracey]

Godot version

v4.0.dev.20211210.official [21b8199]

System information

Kubuntu 21.04, NVIDIA GTX1080, X11, nvidia-driver-470, Vulkan clustered and mobile, Intel i7-7700

Issue description

For me only a partial pointlight2d shadow is generated, and only from certain directions:

And no shadow from other directions:

Directional shadows work perfectly:

Same result on both clustered & mobile. Changing the occluder shape has no effect.

Have tested on the last 3 builds, and on the oldest build up on the tuxfamily download list.

Steps to reproduce

Create a new project, make a new 2d scene and add a background (sprite or polygon2d), PointLight2d and texture, LightOccluder2d and occluder polygon.

Turn on shadows on the light and move it around the occluder.

Minimal reproduction project

point2dshadows.zip

[sakrel]

this call to draw_list_begin in light_update_shadow seems to clear the entire shadow atlas instead of the rect that is supposed to be drawn to:

godot/servers/rendering/renderer_rd/renderer_canvas_render_rd.cpp

Lines 1555 to 1561 in bdf8340

	for (int i = 0; i < 4; i++) {
	//make sure it remains orthogonal, makes easy to read angle later
	//light.basis.scale(Vector3(to_light.elements[0].length(),to_light.elements[1].length(),1));
	Rect2i rect((state.shadow_texture_size / 4) * i, p_shadow_index * 2, (state.shadow_texture_size / 4), 2);
	RD::DrawListID draw_list = RD::get_singleton()->draw_list_begin(state.shadow_fb, RD::INITIAL_ACTION_CLEAR, RD::FINAL_ACTION_READ, RD::INITIAL_ACTION_CLEAR, RD::FINAL_ACTION_DISCARD, cc, 1.0, 0, rect);

[h0lley]

this broke on Jan 25, 2021, commit 71f0b4f, where reduz' PR #45376 got merged.
unfortunately it's quite a large PR, so I can't boil it down any further.