Fix shadows for billboarded Sprite3D's

doc/classes/BaseMaterial3D.xml

@@ -125,6 +125,7 @@
 		</member>
 		<member name="billboard_mode" type="int" setter="set_billboard_mode" getter="get_billboard_mode" enum="BaseMaterial3D.BillboardMode" default="0">
 			Controls how the object faces the camera. See [enum BillboardMode].
+			[b]Note:[/b] When billboarding is enabled and the material also casts shadows, billboards will face [b]the[/b] camera in the scene when rendering shadows. In scenes with multiple cameras, the intended shadow cannot be determined and this will result in undefined behavior. See [url=https://github.com/godotengine/godot/pull/72638]GitHub Pull Request #72638[/url] for details.
 			[b]Note:[/b] Billboard mode is not suitable for VR because the left-right vector of the camera is not horizontal when the screen is attached to your head instead of on the table. See [url=https://github.com/godotengine/godot/issues/41567]GitHub issue #41567[/url] for details.
 		</member>
 		<member name="blend_mode" type="int" setter="set_blend_mode" getter="get_blend_mode" enum="BaseMaterial3D.BlendMode" default="0">

doc/classes/SpriteBase3D.xml

@@ -58,6 +58,7 @@
 		</member>
 		<member name="billboard" type="int" setter="set_billboard_mode" getter="get_billboard_mode" enum="BaseMaterial3D.BillboardMode" default="0">
 			The billboard mode to use for the sprite. See [enum BaseMaterial3D.BillboardMode] for possible values.
+			[b]Note:[/b] When billboarding is enabled and the material also casts shadows, billboards will face [b]the[/b] camera in the scene when rendering shadows. In scenes with multiple cameras, the intended shadow cannot be determined and this will result in undefined behavior. See [url=https://github.com/godotengine/godot/pull/72638]GitHub Pull Request #72638[/url] for details.
 		</member>
 		<member name="centered" type="bool" setter="set_centered" getter="is_centered" default="true">
 			If [code]true[/code], texture will be centered.

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -1555,6 +1555,7 @@ void RasterizerSceneGLES3::_setup_environment(const RenderDataGLES3 *p_render_da
 	GLES3::MaterialStorage::store_camera(projection.inverse(), scene_state.ubo.inv_projection_matrix);
 	GLES3::MaterialStorage::store_transform(p_render_data->cam_transform, scene_state.ubo.inv_view_matrix);
 	GLES3::MaterialStorage::store_transform(p_render_data->inv_cam_transform, scene_state.ubo.view_matrix);
+	GLES3::MaterialStorage::store_transform(p_render_data->main_cam_transform, scene_state.ubo.main_cam_inv_view_matrix);
 	scene_state.ubo.camera_visible_layers = p_render_data->camera_visible_layers;
 
 	if (p_render_data->view_count > 1) {
@@ -2095,20 +2096,20 @@ void RasterizerSceneGLES3::_render_shadows(const RenderDataGLES3 *p_render_data,
 
 		// Render cubemap shadows.
 		for (const int &index : cube_shadows) {
-			_render_shadow_pass(p_render_data->render_shadows[index].light, p_render_data->shadow_atlas, p_render_data->render_shadows[index].pass, p_render_data->render_shadows[index].instances, camera_plane, lod_distance_multiplier, p_render_data->screen_mesh_lod_threshold, p_render_data->render_info, p_viewport_size);
+			_render_shadow_pass(p_render_data->render_shadows[index].light, p_render_data->shadow_atlas, p_render_data->render_shadows[index].pass, p_render_data->render_shadows[index].instances, camera_plane, lod_distance_multiplier, p_render_data->screen_mesh_lod_threshold, p_render_data->render_info, p_viewport_size, p_render_data->cam_transform);
 		}
 		// Render directional shadows.
 		for (uint32_t i = 0; i < directional_shadows.size(); i++) {
-			_render_shadow_pass(p_render_data->render_shadows[directional_shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[directional_shadows[i]].pass, p_render_data->render_shadows[directional_shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->screen_mesh_lod_threshold, p_render_data->render_info, p_viewport_size);
+			_render_shadow_pass(p_render_data->render_shadows[directional_shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[directional_shadows[i]].pass, p_render_data->render_shadows[directional_shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->screen_mesh_lod_threshold, p_render_data->render_info, p_viewport_size, p_render_data->cam_transform);
 		}
 		// Render positional shadows (Spotlight and Omnilight with dual-paraboloid).
 		for (uint32_t i = 0; i < shadows.size(); i++) {
-			_render_shadow_pass(p_render_data->render_shadows[shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[shadows[i]].pass, p_render_data->render_shadows[shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->screen_mesh_lod_threshold, p_render_data->render_info, p_viewport_size);
+			_render_shadow_pass(p_render_data->render_shadows[shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[shadows[i]].pass, p_render_data->render_shadows[shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->screen_mesh_lod_threshold, p_render_data->render_info, p_viewport_size, p_render_data->cam_transform);
 		}
 	}
 }
 
-void RasterizerSceneGLES3::_render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, RenderingMethod::RenderInfo *p_render_info, const Size2i &p_viewport_size) {
+void RasterizerSceneGLES3::_render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, RenderingMethod::RenderInfo *p_render_info, const Size2i &p_viewport_size, const Transform3D &p_main_cam_transform) {
 	GLES3::LightStorage *light_storage = GLES3::LightStorage::get_singleton();
 
 	ERR_FAIL_COND(!light_storage->owns_light_instance(p_light));
@@ -2242,6 +2243,7 @@ void RasterizerSceneGLES3::_render_shadow_pass(RID p_light, RID p_shadow_atlas,
 	render_data.z_far = zfar; // Only used by OmniLights.
 	render_data.z_near = 0.0;
 	render_data.lod_distance_multiplier = p_lod_distance_multiplier;
+	render_data.main_cam_transform = p_main_cam_transform;
 
 	render_data.instances = &p_instances;
 	render_data.render_info = p_render_info;
@@ -2330,6 +2332,7 @@ void RasterizerSceneGLES3::render_scene(const Ref<RenderSceneBuffers> &p_render_
 		render_data.cam_projection = p_camera_data->main_projection;
 		render_data.cam_orthogonal = p_camera_data->is_orthogonal;
 		render_data.camera_visible_layers = p_camera_data->visible_layers;
+		render_data.main_cam_transform = p_camera_data->main_transform;
 
 		render_data.view_count = p_camera_data->view_count;
 		for (uint32_t v = 0; v < p_camera_data->view_count; v++) {
@@ -3448,6 +3451,7 @@ void RasterizerSceneGLES3::render_particle_collider_heightfield(RID p_collider,
 	render_data.cam_orthogonal = true;
 	render_data.z_near = 0.0;
 	render_data.z_far = cm.get_z_far();
+	render_data.main_cam_transform = cam_xform;
 
 	render_data.instances = &p_instances;
 

drivers/gles3/rasterizer_scene_gles3.h

@@ -98,6 +98,9 @@ struct RenderDataGLES3 {
 	bool cam_orthogonal = false;
 	uint32_t camera_visible_layers = 0xFFFFFFFF;
 
+	// For billboards to cast correct shadows.
+	Transform3D main_cam_transform;
+
 	// For stereo rendering
 	uint32_t view_count = 1;
 	Vector3 view_eye_offset[RendererSceneRender::MAX_RENDER_VIEWS];
@@ -370,6 +373,8 @@ private:
 			float inv_view_matrix[16];
 			float view_matrix[16];
 
+			float main_cam_inv_view_matrix[16];
+
 			float viewport_size[2];
 			float screen_pixel_size[2];
 
@@ -538,7 +543,7 @@ private:
 	void _setup_environment(const RenderDataGLES3 *p_render_data, bool p_no_fog, const Size2i &p_screen_size, bool p_flip_y, const Color &p_default_bg_color, bool p_pancake_shadows, float p_shadow_bias = 0.0);
 	void _fill_render_list(RenderListType p_render_list, const RenderDataGLES3 *p_render_data, PassMode p_pass_mode, bool p_append = false);
 	void _render_shadows(const RenderDataGLES3 *p_render_data, const Size2i &p_viewport_size = Size2i(1, 1));
-	void _render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0, float p_screen_mesh_lod_threshold = 0.0, RenderingMethod::RenderInfo *p_render_info = nullptr, const Size2i &p_viewport_size = Size2i(1, 1));
+	void _render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0, float p_screen_mesh_lod_threshold = 0.0, RenderingMethod::RenderInfo *p_render_info = nullptr, const Size2i &p_viewport_size = Size2i(1, 1), const Transform3D &p_main_cam_transform = Transform3D());
 	void _render_post_processing(const RenderDataGLES3 *p_render_data);
 
 	template <PassMode p_pass_mode>

drivers/gles3/shaders/scene.glsl

@@ -155,6 +155,9 @@ layout(std140) uniform SceneData { // ubo:2
 	highp mat4 inv_view_matrix;
 	highp mat4 view_matrix;
 
+	// Used for billboards to cast correct shadows.
+	highp mat4 main_cam_inv_view_matrix;
+
 	vec2 viewport_size;
 	vec2 screen_pixel_size;
 
@@ -637,6 +640,9 @@ layout(std140) uniform SceneData { // ubo:2
 	highp mat4 inv_view_matrix;
 	highp mat4 view_matrix;
 
+	// Used for billboards to cast correct shadows.
+	highp mat4 main_cam_inv_view_matrix;
+
 	vec2 viewport_size;
 	vec2 screen_pixel_size;
 

drivers/gles3/storage/material_storage.cpp

@@ -1209,6 +1209,7 @@ MaterialStorage::MaterialStorage() {
 		actions.renames["INV_PROJECTION_MATRIX"] = "inv_projection_matrix";
 		actions.renames["MODELVIEW_MATRIX"] = "modelview";
 		actions.renames["MODELVIEW_NORMAL_MATRIX"] = "modelview_normal";
+		actions.renames["MAIN_CAM_INV_VIEW_MATRIX"] = "scene_data.main_cam_inv_view_matrix";
 
 		actions.renames["VERTEX"] = "vertex";
 		actions.renames["NORMAL"] = "normal";

scene/resources/material.cpp

@@ -991,7 +991,8 @@ void BaseMaterial3D::_update_shader() {
 		case BILLBOARD_DISABLED: {
 		} break;
 		case BILLBOARD_ENABLED: {
-			code += "	MODELVIEW_MATRIX = VIEW_MATRIX * mat4(INV_VIEW_MATRIX[0], INV_VIEW_MATRIX[1], INV_VIEW_MATRIX[2], MODEL_MATRIX[3]);\n";
+			// MAIN_CAM_INV_VIEW_MATRIX is inverse of the camera, even on shadow passes: this ensures the billboard faces the camera when casting shadows.
+			code += "	MODELVIEW_MATRIX = VIEW_MATRIX * mat4(MAIN_CAM_INV_VIEW_MATRIX[0], MAIN_CAM_INV_VIEW_MATRIX[1], MAIN_CAM_INV_VIEW_MATRIX[2], MODEL_MATRIX[3]);\n";
 
 			if (flags[FLAG_BILLBOARD_KEEP_SCALE]) {
 				code += "	MODELVIEW_MATRIX = MODELVIEW_MATRIX * mat4(vec4(length(MODEL_MATRIX[0].xyz), 0.0, 0.0, 0.0), vec4(0.0, length(MODEL_MATRIX[1].xyz), 0.0, 0.0), vec4(0.0, 0.0, length(MODEL_MATRIX[2].xyz), 0.0), vec4(0.0, 0.0, 0.0, 1.0));\n";
@@ -999,10 +1000,11 @@ void BaseMaterial3D::_update_shader() {
 			code += "	MODELVIEW_NORMAL_MATRIX = mat3(MODELVIEW_MATRIX);\n";
 		} break;
 		case BILLBOARD_FIXED_Y: {
-			code += "	MODELVIEW_MATRIX = VIEW_MATRIX * mat4(vec4(normalize(cross(vec3(0.0, 1.0, 0.0), INV_VIEW_MATRIX[2].xyz)), 0.0), vec4(0.0, 1.0, 0.0, 0.0), vec4(normalize(cross(INV_VIEW_MATRIX[0].xyz, vec3(0.0, 1.0, 0.0))), 0.0), MODEL_MATRIX[3]);\n";
+			// MAIN_CAM_INV_VIEW_MATRIX is inverse of the camera, even on shadow passes: this ensures the billboard faces the camera when casting shadows.
+			code += "	MODELVIEW_MATRIX = VIEW_MATRIX * mat4(vec4(normalize(cross(vec3(0.0, 1.0, 0.0), MAIN_CAM_INV_VIEW_MATRIX[2].xyz)), 0.0), vec4(0.0, 1.0, 0.0, 0.0), vec4(normalize(cross(MAIN_CAM_INV_VIEW_MATRIX[0].xyz, vec3(0.0, 1.0, 0.0))), 0.0), MODEL_MATRIX[3]);\n";
 
 			if (flags[FLAG_BILLBOARD_KEEP_SCALE]) {
-				code += "	MODELVIEW_MATRIX = MODELVIEW_MATRIX * mat4(vec4(length(MODEL_MATRIX[0].xyz), 0.0, 0.0, 0.0),vec4(0.0, length(MODEL_MATRIX[1].xyz), 0.0, 0.0), vec4(0.0, 0.0, length(MODEL_MATRIX[2].xyz), 0.0), vec4(0.0, 0.0, 0.0, 1.0));\n";
+				code += "	MODELVIEW_MATRIX = MODELVIEW_MATRIX * mat4(vec4(length(MODEL_MATRIX[0].xyz), 0.0, 0.0, 0.0), vec4(0.0, length(MODEL_MATRIX[1].xyz), 0.0, 0.0), vec4(0.0, 0.0, length(MODEL_MATRIX[2].xyz), 0.0), vec4(0.0, 0.0, 0.0, 1.0));\n";
 			}
 			code += "	MODELVIEW_NORMAL_MATRIX = mat3(MODELVIEW_MATRIX);\n";
 		} break;

servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp

@@ -1403,7 +1403,7 @@ void RenderForwardClustered::_pre_opaque_render(RenderDataRD *p_render_data, boo
 
 		//cube shadows are rendered in their own way
 		for (const int &index : p_render_data->cube_shadows) {
-			_render_shadow_pass(p_render_data->render_shadows[index].light, p_render_data->shadow_atlas, p_render_data->render_shadows[index].pass, p_render_data->render_shadows[index].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, true, true, true, p_render_data->render_info, viewport_size);
+			_render_shadow_pass(p_render_data->render_shadows[index].light, p_render_data->shadow_atlas, p_render_data->render_shadows[index].pass, p_render_data->render_shadows[index].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, true, true, true, p_render_data->render_info, viewport_size, p_render_data->scene_data->cam_transform);
 		}
 
 		if (p_render_data->directional_shadows.size()) {
@@ -1433,11 +1433,11 @@ void RenderForwardClustered::_pre_opaque_render(RenderDataRD *p_render_data, boo
 
 		//render directional shadows
 		for (uint32_t i = 0; i < p_render_data->directional_shadows.size(); i++) {
-			_render_shadow_pass(p_render_data->render_shadows[p_render_data->directional_shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->directional_shadows[i]].pass, p_render_data->render_shadows[p_render_data->directional_shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, false, i == p_render_data->directional_shadows.size() - 1, false, p_render_data->render_info, viewport_size);
+			_render_shadow_pass(p_render_data->render_shadows[p_render_data->directional_shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->directional_shadows[i]].pass, p_render_data->render_shadows[p_render_data->directional_shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, false, i == p_render_data->directional_shadows.size() - 1, false, p_render_data->render_info, viewport_size, p_render_data->scene_data->cam_transform);
 		}
 		//render positional shadows
 		for (uint32_t i = 0; i < p_render_data->shadows.size(); i++) {
-			_render_shadow_pass(p_render_data->render_shadows[p_render_data->shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->shadows[i]].pass, p_render_data->render_shadows[p_render_data->shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, i == 0, i == p_render_data->shadows.size() - 1, true, p_render_data->render_info, viewport_size);
+			_render_shadow_pass(p_render_data->render_shadows[p_render_data->shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->shadows[i]].pass, p_render_data->render_shadows[p_render_data->shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, i == 0, i == p_render_data->shadows.size() - 1, true, p_render_data->render_info, viewport_size, p_render_data->scene_data->cam_transform);
 		}
 
 		_render_shadow_process();
@@ -2268,7 +2268,7 @@ void RenderForwardClustered::_render_buffers_debug_draw(const RenderDataRD *p_re
 	}
 }
 
-void RenderForwardClustered::_render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, bool p_open_pass, bool p_close_pass, bool p_clear_region, RenderingMethod::RenderInfo *p_render_info, const Size2i &p_viewport_size) {
+void RenderForwardClustered::_render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, bool p_open_pass, bool p_close_pass, bool p_clear_region, RenderingMethod::RenderInfo *p_render_info, const Size2i &p_viewport_size, const Transform3D &p_main_cam_transform) {
 	RendererRD::LightStorage *light_storage = RendererRD::LightStorage::get_singleton();
 
 	ERR_FAIL_COND(!light_storage->owns_light_instance(p_light));
@@ -2423,7 +2423,7 @@ void RenderForwardClustered::_render_shadow_pass(RID p_light, RID p_shadow_atlas
 
 	if (render_cubemap) {
 		//rendering to cubemap
-		_render_shadow_append(render_fb, p_instances, light_projection, light_transform, zfar, 0, 0, reverse_cull_face, false, false, use_pancake, p_camera_plane, p_lod_distance_multiplier, p_screen_mesh_lod_threshold, Rect2(), false, true, true, true, p_render_info, p_viewport_size);
+		_render_shadow_append(render_fb, p_instances, light_projection, light_transform, zfar, 0, 0, reverse_cull_face, false, false, use_pancake, p_camera_plane, p_lod_distance_multiplier, p_screen_mesh_lod_threshold, Rect2(), false, true, true, true, p_render_info, p_viewport_size, p_main_cam_transform);
 		if (finalize_cubemap) {
 			_render_shadow_process();
 			_render_shadow_end();
@@ -2441,7 +2441,7 @@ void RenderForwardClustered::_render_shadow_pass(RID p_light, RID p_shadow_atlas
 
 	} else {
 		//render shadow
-		_render_shadow_append(render_fb, p_instances, light_projection, light_transform, zfar, 0, 0, reverse_cull_face, using_dual_paraboloid, using_dual_paraboloid_flip, use_pancake, p_camera_plane, p_lod_distance_multiplier, p_screen_mesh_lod_threshold, atlas_rect, flip_y, p_clear_region, p_open_pass, p_close_pass, p_render_info, p_viewport_size);
+		_render_shadow_append(render_fb, p_instances, light_projection, light_transform, zfar, 0, 0, reverse_cull_face, using_dual_paraboloid, using_dual_paraboloid_flip, use_pancake, p_camera_plane, p_lod_distance_multiplier, p_screen_mesh_lod_threshold, atlas_rect, flip_y, p_clear_region, p_open_pass, p_close_pass, p_render_info, p_viewport_size, p_main_cam_transform);
 	}
 }
 
@@ -2454,7 +2454,7 @@ void RenderForwardClustered::_render_shadow_begin() {
 	scene_state.instance_data[RENDER_LIST_SECONDARY].clear();
 }
 
-void RenderForwardClustered::_render_shadow_append(RID p_framebuffer, const PagedArray<RenderGeometryInstance *> &p_instances, const Projection &p_projection, const Transform3D &p_transform, float p_zfar, float p_bias, float p_normal_bias, bool p_reverse_cull_face, bool p_use_dp, bool p_use_dp_flip, bool p_use_pancake, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, const Rect2i &p_rect, bool p_flip_y, bool p_clear_region, bool p_begin, bool p_end, RenderingMethod::RenderInfo *p_render_info, const Size2i &p_viewport_size) {
+void RenderForwardClustered::_render_shadow_append(RID p_framebuffer, const PagedArray<RenderGeometryInstance *> &p_instances, const Projection &p_projection, const Transform3D &p_transform, float p_zfar, float p_bias, float p_normal_bias, bool p_reverse_cull_face, bool p_use_dp, bool p_use_dp_flip, bool p_use_pancake, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, const Rect2i &p_rect, bool p_flip_y, bool p_clear_region, bool p_begin, bool p_end, RenderingMethod::RenderInfo *p_render_info, const Size2i &p_viewport_size, const Transform3D &p_main_cam_transform) {
 	uint32_t shadow_pass_index = scene_state.shadow_passes.size();
 
 	SceneState::ShadowPass shadow_pass;
@@ -2470,6 +2470,7 @@ void RenderForwardClustered::_render_shadow_append(RID p_framebuffer, const Page
 	scene_data.opaque_prepass_threshold = 0.1f;
 	scene_data.time = time;
 	scene_data.time_step = time_step;
+	scene_data.main_cam_transform = p_main_cam_transform;
 
 	RenderDataRD render_data;
 	render_data.scene_data = &scene_data;
@@ -2561,6 +2562,7 @@ void RenderForwardClustered::_render_particle_collider_heightfield(RID p_fb, con
 	scene_data.opaque_prepass_threshold = 0.0;
 	scene_data.time = time;
 	scene_data.time_step = time_step;
+	scene_data.main_cam_transform = p_cam_transform;
 
 	RenderDataRD render_data;
 	render_data.scene_data = &scene_data;
@@ -2605,6 +2607,7 @@ void RenderForwardClustered::_render_material(const Transform3D &p_cam_transform
 	scene_data.emissive_exposure_normalization = p_exposure_normalization;
 	scene_data.time = time;
 	scene_data.time_step = time_step;
+	scene_data.main_cam_transform = p_cam_transform;
 
 	RenderDataRD render_data;
 	render_data.scene_data = &scene_data;

servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.h

@@ -591,9 +591,9 @@ class RenderForwardClustered : public RendererSceneRenderRD {
 
 	/* Render shadows */
 
-	void _render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0, float p_screen_mesh_lod_threshold = 0.0, bool p_open_pass = true, bool p_close_pass = true, bool p_clear_region = true, RenderingMethod::RenderInfo *p_render_info = nullptr, const Size2i &p_viewport_size = Size2i(1, 1));
+	void _render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0, float p_screen_mesh_lod_threshold = 0.0, bool p_open_pass = true, bool p_close_pass = true, bool p_clear_region = true, RenderingMethod::RenderInfo *p_render_info = nullptr, const Size2i &p_viewport_size = Size2i(1, 1), const Transform3D &p_main_cam_transform = Transform3D());
 	void _render_shadow_begin();
-	void _render_shadow_append(RID p_framebuffer, const PagedArray<RenderGeometryInstance *> &p_instances, const Projection &p_projection, const Transform3D &p_transform, float p_zfar, float p_bias, float p_normal_bias, bool p_reverse_cull_face, bool p_use_dp, bool p_use_dp_flip, bool p_use_pancake, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0.0, float p_screen_mesh_lod_threshold = 0.0, const Rect2i &p_rect = Rect2i(), bool p_flip_y = false, bool p_clear_region = true, bool p_begin = true, bool p_end = true, RenderingMethod::RenderInfo *p_render_info = nullptr, const Size2i &p_viewport_size = Size2i(1, 1));
+	void _render_shadow_append(RID p_framebuffer, const PagedArray<RenderGeometryInstance *> &p_instances, const Projection &p_projection, const Transform3D &p_transform, float p_zfar, float p_bias, float p_normal_bias, bool p_reverse_cull_face, bool p_use_dp, bool p_use_dp_flip, bool p_use_pancake, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0.0, float p_screen_mesh_lod_threshold = 0.0, const Rect2i &p_rect = Rect2i(), bool p_flip_y = false, bool p_clear_region = true, bool p_begin = true, bool p_end = true, RenderingMethod::RenderInfo *p_render_info = nullptr, const Size2i &p_viewport_size = Size2i(1, 1), const Transform3D &p_main_cam_transform = Transform3D());
 	void _render_shadow_process();
 	void _render_shadow_end();
 

servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp

@@ -559,6 +559,7 @@ void SceneShaderForwardClustered::init(const String p_defines) {
 		actions.renames["INV_PROJECTION_MATRIX"] = "inv_projection_matrix";
 		actions.renames["MODELVIEW_MATRIX"] = "modelview";
 		actions.renames["MODELVIEW_NORMAL_MATRIX"] = "modelview_normal";
+		actions.renames["MAIN_CAM_INV_VIEW_MATRIX"] = "scene_data.main_cam_inv_view_matrix";
 
 		actions.renames["VERTEX"] = "vertex";
 		actions.renames["NORMAL"] = "normal";

servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp

@@ -608,7 +608,7 @@ void RenderForwardMobile::_pre_opaque_render(RenderDataRD *p_render_data) {
 
 		//cube shadows are rendered in their own way
 		for (const int &index : p_render_data->cube_shadows) {
-			_render_shadow_pass(p_render_data->render_shadows[index].light, p_render_data->shadow_atlas, p_render_data->render_shadows[index].pass, p_render_data->render_shadows[index].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, true, true, true, p_render_data->render_info);
+			_render_shadow_pass(p_render_data->render_shadows[index].light, p_render_data->shadow_atlas, p_render_data->render_shadows[index].pass, p_render_data->render_shadows[index].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, true, true, true, p_render_data->render_info, p_render_data->scene_data->cam_transform);
 		}
 
 		if (p_render_data->directional_shadows.size()) {
@@ -629,11 +629,11 @@ void RenderForwardMobile::_pre_opaque_render(RenderDataRD *p_render_data) {
 
 		//render directional shadows
 		for (uint32_t i = 0; i < p_render_data->directional_shadows.size(); i++) {
-			_render_shadow_pass(p_render_data->render_shadows[p_render_data->directional_shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->directional_shadows[i]].pass, p_render_data->render_shadows[p_render_data->directional_shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, false, i == p_render_data->directional_shadows.size() - 1, false, p_render_data->render_info);
+			_render_shadow_pass(p_render_data->render_shadows[p_render_data->directional_shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->directional_shadows[i]].pass, p_render_data->render_shadows[p_render_data->directional_shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, false, i == p_render_data->directional_shadows.size() - 1, false, p_render_data->render_info, p_render_data->scene_data->cam_transform);
 		}
 		//render positional shadows
 		for (uint32_t i = 0; i < p_render_data->shadows.size(); i++) {
-			_render_shadow_pass(p_render_data->render_shadows[p_render_data->shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->shadows[i]].pass, p_render_data->render_shadows[p_render_data->shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, i == 0, i == p_render_data->shadows.size() - 1, true, p_render_data->render_info);
+			_render_shadow_pass(p_render_data->render_shadows[p_render_data->shadows[i]].light, p_render_data->shadow_atlas, p_render_data->render_shadows[p_render_data->shadows[i]].pass, p_render_data->render_shadows[p_render_data->shadows[i]].instances, camera_plane, lod_distance_multiplier, p_render_data->scene_data->screen_mesh_lod_threshold, i == 0, i == p_render_data->shadows.size() - 1, true, p_render_data->render_info, p_render_data->scene_data->cam_transform);
 		}
 
 		_render_shadow_process();
@@ -1068,7 +1068,7 @@ void RenderForwardMobile::_render_scene(RenderDataRD *p_render_data, const Color
 
 /* these are being called from RendererSceneRenderRD::_pre_opaque_render */
 
-void RenderForwardMobile::_render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, bool p_open_pass, bool p_close_pass, bool p_clear_region, RenderingMethod::RenderInfo *p_render_info) {
+void RenderForwardMobile::_render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, bool p_open_pass, bool p_close_pass, bool p_clear_region, RenderingMethod::RenderInfo *p_render_info, const Transform3D &p_main_cam_transform) {
 	RendererRD::LightStorage *light_storage = RendererRD::LightStorage::get_singleton();
 
 	ERR_FAIL_COND(!light_storage->owns_light_instance(p_light));
@@ -1222,7 +1222,7 @@ void RenderForwardMobile::_render_shadow_pass(RID p_light, RID p_shadow_atlas, i
 
 	if (render_cubemap) {
 		//rendering to cubemap
-		_render_shadow_append(render_fb, p_instances, light_projection, light_transform, zfar, 0, 0, false, false, use_pancake, p_camera_plane, p_lod_distance_multiplier, p_screen_mesh_lod_threshold, Rect2(), false, true, true, true, p_render_info);
+		_render_shadow_append(render_fb, p_instances, light_projection, light_transform, zfar, 0, 0, false, false, use_pancake, p_camera_plane, p_lod_distance_multiplier, p_screen_mesh_lod_threshold, Rect2(), false, true, true, true, p_render_info, p_main_cam_transform);
 		if (finalize_cubemap) {
 			_render_shadow_process();
 			_render_shadow_end();
@@ -1241,7 +1241,7 @@ void RenderForwardMobile::_render_shadow_pass(RID p_light, RID p_shadow_atlas, i
 
 	} else {
 		//render shadow
-		_render_shadow_append(render_fb, p_instances, light_projection, light_transform, zfar, 0, 0, using_dual_paraboloid, using_dual_paraboloid_flip, use_pancake, p_camera_plane, p_lod_distance_multiplier, p_screen_mesh_lod_threshold, atlas_rect, flip_y, p_clear_region, p_open_pass, p_close_pass, p_render_info);
+		_render_shadow_append(render_fb, p_instances, light_projection, light_transform, zfar, 0, 0, using_dual_paraboloid, using_dual_paraboloid_flip, use_pancake, p_camera_plane, p_lod_distance_multiplier, p_screen_mesh_lod_threshold, atlas_rect, flip_y, p_clear_region, p_open_pass, p_close_pass, p_render_info, p_main_cam_transform);
 	}
 }
 
@@ -1253,7 +1253,7 @@ void RenderForwardMobile::_render_shadow_begin() {
 	render_list[RENDER_LIST_SECONDARY].clear();
 }
 
-void RenderForwardMobile::_render_shadow_append(RID p_framebuffer, const PagedArray<RenderGeometryInstance *> &p_instances, const Projection &p_projection, const Transform3D &p_transform, float p_zfar, float p_bias, float p_normal_bias, bool p_use_dp, bool p_use_dp_flip, bool p_use_pancake, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, const Rect2i &p_rect, bool p_flip_y, bool p_clear_region, bool p_begin, bool p_end, RenderingMethod::RenderInfo *p_render_info) {
+void RenderForwardMobile::_render_shadow_append(RID p_framebuffer, const PagedArray<RenderGeometryInstance *> &p_instances, const Projection &p_projection, const Transform3D &p_transform, float p_zfar, float p_bias, float p_normal_bias, bool p_use_dp, bool p_use_dp_flip, bool p_use_pancake, const Plane &p_camera_plane, float p_lod_distance_multiplier, float p_screen_mesh_lod_threshold, const Rect2i &p_rect, bool p_flip_y, bool p_clear_region, bool p_begin, bool p_end, RenderingMethod::RenderInfo *p_render_info, const Transform3D &p_main_cam_transform) {
 	uint32_t shadow_pass_index = scene_state.shadow_passes.size();
 
 	SceneState::ShadowPass shadow_pass;
@@ -1274,6 +1274,7 @@ void RenderForwardMobile::_render_shadow_append(RID p_framebuffer, const PagedAr
 	scene_data.opaque_prepass_threshold = 0.1;
 	scene_data.time = time;
 	scene_data.time_step = time_step;
+	scene_data.main_cam_transform = p_main_cam_transform;
 
 	RenderDataRD render_data;
 	render_data.scene_data = &scene_data;
@@ -1363,6 +1364,7 @@ void RenderForwardMobile::_render_material(const Transform3D &p_cam_transform, c
 	scene_data.emissive_exposure_normalization = p_exposure_normalization;
 	scene_data.time = time;
 	scene_data.time_step = time_step;
+	scene_data.main_cam_transform = p_cam_transform;
 
 	RenderDataRD render_data;
 	render_data.scene_data = &scene_data;
@@ -1488,6 +1490,7 @@ void RenderForwardMobile::_render_particle_collider_heightfield(RID p_fb, const
 	scene_data.opaque_prepass_threshold = 0.0;
 	scene_data.time = time;
 	scene_data.time_step = time_step;
+	scene_data.main_cam_transform = p_cam_transform;
 
 	RenderDataRD render_data;
 	render_data.scene_data = &scene_data;

servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.h

@@ -177,9 +177,9 @@ private:
 
 	/* Render shadows */
 
-	void _render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0, float p_screen_mesh_lod_threshold = 0.0, bool p_open_pass = true, bool p_close_pass = true, bool p_clear_region = true, RenderingMethod::RenderInfo *p_render_info = nullptr);
+	void _render_shadow_pass(RID p_light, RID p_shadow_atlas, int p_pass, const PagedArray<RenderGeometryInstance *> &p_instances, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0, float p_screen_mesh_lod_threshold = 0.0, bool p_open_pass = true, bool p_close_pass = true, bool p_clear_region = true, RenderingMethod::RenderInfo *p_render_info = nullptr, const Transform3D &p_main_cam_transform = Transform3D());
 	void _render_shadow_begin();
-	void _render_shadow_append(RID p_framebuffer, const PagedArray<RenderGeometryInstance *> &p_instances, const Projection &p_projection, const Transform3D &p_transform, float p_zfar, float p_bias, float p_normal_bias, bool p_use_dp, bool p_use_dp_flip, bool p_use_pancake, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0.0, float p_screen_mesh_lod_threshold = 0.0, const Rect2i &p_rect = Rect2i(), bool p_flip_y = false, bool p_clear_region = true, bool p_begin = true, bool p_end = true, RenderingMethod::RenderInfo *p_render_info = nullptr);
+	void _render_shadow_append(RID p_framebuffer, const PagedArray<RenderGeometryInstance *> &p_instances, const Projection &p_projection, const Transform3D &p_transform, float p_zfar, float p_bias, float p_normal_bias, bool p_use_dp, bool p_use_dp_flip, bool p_use_pancake, const Plane &p_camera_plane = Plane(), float p_lod_distance_multiplier = 0.0, float p_screen_mesh_lod_threshold = 0.0, const Rect2i &p_rect = Rect2i(), bool p_flip_y = false, bool p_clear_region = true, bool p_begin = true, bool p_end = true, RenderingMethod::RenderInfo *p_render_info = nullptr, const Transform3D &p_main_cam_transform = Transform3D());
 	void _render_shadow_process();
 	void _render_shadow_end();
 

servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp

@@ -463,6 +463,7 @@ void SceneShaderForwardMobile::init(const String p_defines) {
 		actions.renames["INV_PROJECTION_MATRIX"] = "inv_projection_matrix";
 		actions.renames["MODELVIEW_MATRIX"] = "modelview";
 		actions.renames["MODELVIEW_NORMAL_MATRIX"] = "modelview_normal";
+		actions.renames["MAIN_CAM_INV_VIEW_MATRIX"] = "scene_data.main_cam_inv_view_matrix";
 
 		actions.renames["VERTEX"] = "vertex";
 		actions.renames["NORMAL"] = "normal";

servers/rendering/renderer_rd/renderer_scene_render_rd.cpp

@@ -1005,6 +1005,7 @@ void RendererSceneRenderRD::render_scene(const Ref<RenderSceneBuffers> &p_render
 		scene_data.cam_orthogonal = p_camera_data->is_orthogonal;
 		scene_data.camera_visible_layers = p_camera_data->visible_layers;
 		scene_data.taa_jitter = p_camera_data->taa_jitter;
+		scene_data.main_cam_transform = p_camera_data->main_transform;
 
 		scene_data.view_count = p_camera_data->view_count;
 		for (uint32_t v = 0; v < p_camera_data->view_count; v++) {

servers/rendering/renderer_rd/shaders/scene_data_inc.glsl

@@ -14,6 +14,9 @@ struct SceneData {
 	highp mat4 inv_projection_matrix_view[MAX_VIEWS];
 	highp vec4 eye_offset[MAX_VIEWS];
 
+	// Used for billboards to cast correct shadows.
+	highp mat4 main_cam_inv_view_matrix;
+
 	highp vec2 viewport_size;
 	highp vec2 screen_pixel_size;
 

servers/rendering/renderer_rd/storage_rd/render_scene_data_rd.cpp

@@ -76,6 +76,8 @@ void RenderSceneDataRD::update_ubo(RID p_uniform_buffer, RS::ViewportDebugDraw p
 		ubo.eye_offset[v][3] = 0.0;
 	}
 
+	RendererRD::MaterialStorage::store_transform(main_cam_transform, ubo.main_cam_inv_view_matrix);
+
 	ubo.taa_jitter[0] = taa_jitter.x;
 	ubo.taa_jitter[1] = taa_jitter.y;
 

servers/rendering/renderer_rd/storage_rd/render_scene_data_rd.h

@@ -48,6 +48,9 @@ public:
 	uint32_t camera_visible_layers;
 	bool cam_orthogonal = false;
 
+	// For billboards to cast correct shadows.
+	Transform3D main_cam_transform;
+
 	// For stereo rendering
 	uint32_t view_count = 1;
 	Vector3 view_eye_offset[RendererSceneRender::MAX_RENDER_VIEWS];
@@ -94,6 +97,8 @@ private:
 		float inv_projection_matrix_view[RendererSceneRender::MAX_RENDER_VIEWS][16];
 		float eye_offset[RendererSceneRender::MAX_RENDER_VIEWS][4];
 
+		float main_cam_inv_view_matrix[16];
+
 		float viewport_size[2];
 		float screen_pixel_size[2];
 

servers/rendering/shader_types.cpp

@@ -97,6 +97,7 @@ ShaderTypes::ShaderTypes() {
 	shader_modes[RS::SHADER_SPATIAL].functions["vertex"].built_ins["MODELVIEW_NORMAL_MATRIX"] = ShaderLanguage::TYPE_MAT3;
 	shader_modes[RS::SHADER_SPATIAL].functions["vertex"].built_ins["VIEWPORT_SIZE"] = constt(ShaderLanguage::TYPE_VEC2);
 	shader_modes[RS::SHADER_SPATIAL].functions["vertex"].built_ins["OUTPUT_IS_SRGB"] = constt(ShaderLanguage::TYPE_BOOL);
+	shader_modes[RS::SHADER_SPATIAL].functions["vertex"].built_ins["MAIN_CAM_INV_VIEW_MATRIX"] = constt(ShaderLanguage::TYPE_MAT4);
 
 	shader_modes[RS::SHADER_SPATIAL].functions["vertex"].built_ins["NODE_POSITION_WORLD"] = ShaderLanguage::TYPE_VEC3;
 	shader_modes[RS::SHADER_SPATIAL].functions["vertex"].built_ins["CAMERA_POSITION_WORLD"] = ShaderLanguage::TYPE_VEC3;