Merge pull request #89919 from BlueCube3310/bicubic-lightmap

Implement bicubic sampling for lightmaps

doc/classes/ProjectSettings.xml

@@ -2604,6 +2604,10 @@
 			- Intel GPUs: SYCL libraries
 			If no GPU acceleration is configured on the system, multi-threaded CPU-based denoising will be performed instead. This CPU-based denoising is significantly slower than the JNLM denoiser in most cases.
 		</member>
+		<member name="rendering/lightmapping/lightmap_gi/use_bicubic_filter" type="bool" setter="" getter="" default="true">
+			If [code]true[/code], applies a bicubic filter during lightmap sampling. This makes lightmaps look much smoother, at a moderate performance cost.
+			[b]Note:[/b] The bicubic filter exaggerates the 'bleeding' effect that occurs when a lightmap's resolution is low enough.
+		</member>
 		<member name="rendering/lightmapping/primitive_meshes/texel_size" type="float" setter="" getter="" default="0.2">
 			The texel_size that is used to calculate the [member Mesh.lightmap_size_hint] on [PrimitiveMesh] resources if [member PrimitiveMesh.add_uv2] is enabled.
 		</member>

doc/classes/RenderingServer.xml

@@ -2207,6 +2207,13 @@
 				Set the textures on the given [param lightmap] GI instance to the texture array pointed to by the [param light] RID. If the lightmap texture was baked with [member LightmapGI.directional] set to [code]true[/code], then [param uses_sh] must also be [code]true[/code].
 			</description>
 		</method>
+		<method name="lightmaps_set_bicubic_filter">
+			<return type="void" />
+			<param index="0" name="enable" type="bool" />
+			<description>
+				Toggles whether a bicubic filter should be used when lightmaps are sampled. This smoothens their appearance at a performance cost.
+			</description>
+		</method>
 		<method name="make_sphere_mesh">
 			<return type="RID" />
 			<param index="0" name="latitudes" type="int" />

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -3210,6 +3210,10 @@ void RasterizerSceneGLES3::_render_list_template(RenderListParameters *p_params,
 							if (lm->uses_spherical_harmonics) {
 								spec_constants |= SceneShaderGLES3::USE_SH_LIGHTMAP;
 							}
+
+							if (lightmap_bicubic_upscale) {
+								spec_constants |= SceneShaderGLES3::LIGHTMAP_BICUBIC_FILTER;
+							}
 						} else if (inst->lightmap_sh) {
 							spec_constants |= SceneShaderGLES3::USE_LIGHTMAP_CAPTURE;
 						} else {
@@ -3352,6 +3356,11 @@ void RasterizerSceneGLES3::_render_list_template(RenderListParameters *p_params,
 						Vector4 uv_scale(inst->lightmap_uv_scale.position.x, inst->lightmap_uv_scale.position.y, inst->lightmap_uv_scale.size.x, inst->lightmap_uv_scale.size.y);
 						material_storage->shaders.scene_shader.version_set_uniform(SceneShaderGLES3::LIGHTMAP_UV_SCALE, uv_scale, shader->version, instance_variant, spec_constants);
 
+						if (lightmap_bicubic_upscale) {
+							Vector2 light_texture_size(lm->light_texture_size.x, lm->light_texture_size.y);
+							material_storage->shaders.scene_shader.version_set_uniform(SceneShaderGLES3::LIGHTMAP_TEXTURE_SIZE, light_texture_size, shader->version, instance_variant, spec_constants);
+						}
+
 						float exposure_normalization = 1.0;
 						if (p_render_data->camera_attributes.is_valid()) {
 							float enf = RSG::camera_attributes->camera_attributes_get_exposure_normalization_factor(p_render_data->camera_attributes);
@@ -4047,6 +4056,10 @@ void RasterizerSceneGLES3::decals_set_filter(RS::DecalFilter p_filter) {
 void RasterizerSceneGLES3::light_projectors_set_filter(RS::LightProjectorFilter p_filter) {
 }
 
+void RasterizerSceneGLES3::lightmaps_set_bicubic_filter(bool p_enable) {
+	lightmap_bicubic_upscale = p_enable;
+}
+
 RasterizerSceneGLES3::RasterizerSceneGLES3() {
 	singleton = this;
 
@@ -4060,6 +4073,7 @@ RasterizerSceneGLES3::RasterizerSceneGLES3() {
 
 	positional_soft_shadow_filter_set_quality((RS::ShadowQuality)(int)GLOBAL_GET("rendering/lights_and_shadows/positional_shadow/soft_shadow_filter_quality"));
 	directional_soft_shadow_filter_set_quality((RS::ShadowQuality)(int)GLOBAL_GET("rendering/lights_and_shadows/directional_shadow/soft_shadow_filter_quality"));
+	lightmaps_set_bicubic_filter(GLOBAL_GET("rendering/lightmapping/lightmap_gi/use_bicubic_filter"));
 
 	{
 		// Setup Lights

drivers/gles3/rasterizer_scene_gles3.h

@@ -680,6 +680,8 @@ protected:
 	bool glow_bicubic_upscale = false;
 	RS::EnvironmentSSRRoughnessQuality ssr_roughness_quality = RS::ENV_SSR_ROUGHNESS_QUALITY_LOW;
 
+	bool lightmap_bicubic_upscale = false;
+
 	/* Sky */
 
 	struct SkyGlobals {
@@ -863,6 +865,7 @@ public:
 
 	void decals_set_filter(RS::DecalFilter p_filter) override;
 	void light_projectors_set_filter(RS::LightProjectorFilter p_filter) override;
+	virtual void lightmaps_set_bicubic_filter(bool p_enable) override;
 
 	RasterizerSceneGLES3();
 	~RasterizerSceneGLES3();

drivers/gles3/shaders/scene.glsl

@@ -36,6 +36,7 @@ ADDITIVE_OMNI = false
 ADDITIVE_SPOT = false
 RENDER_MATERIAL = false
 SECOND_REFLECTION_PROBE = false
+LIGHTMAP_BICUBIC_FILTER = false
 
 
 #[vertex]
@@ -925,6 +926,10 @@ uniform lowp uint lightmap_slice;
 uniform highp vec4 lightmap_uv_scale;
 uniform float lightmap_exposure_normalization;
 
+#ifdef LIGHTMAP_BICUBIC_FILTER
+uniform highp vec2 lightmap_texture_size;
+#endif
+
 #ifdef USE_SH_LIGHTMAP
 uniform mediump mat3 lightmap_normal_xform;
 #endif // USE_SH_LIGHTMAP
@@ -1417,6 +1422,67 @@ void reflection_process(samplerCube reflection_map,
 
 #endif // !MODE_RENDER_DEPTH
 
+#ifdef LIGHTMAP_BICUBIC_FILTER
+// w0, w1, w2, and w3 are the four cubic B-spline basis functions
+float w0(float a) {
+	return (1.0 / 6.0) * (a * (a * (-a + 3.0) - 3.0) + 1.0);
+}
+
+float w1(float a) {
+	return (1.0 / 6.0) * (a * a * (3.0 * a - 6.0) + 4.0);
+}
+
+float w2(float a) {
+	return (1.0 / 6.0) * (a * (a * (-3.0 * a + 3.0) + 3.0) + 1.0);
+}
+
+float w3(float a) {
+	return (1.0 / 6.0) * (a * a * a);
+}
+
+// g0 and g1 are the two amplitude functions
+float g0(float a) {
+	return w0(a) + w1(a);
+}
+
+float g1(float a) {
+	return w2(a) + w3(a);
+}
+
+// h0 and h1 are the two offset functions
+float h0(float a) {
+	return -1.0 + w1(a) / (w0(a) + w1(a));
+}
+
+float h1(float a) {
+	return 1.0 + w3(a) / (w2(a) + w3(a));
+}
+
+vec4 textureArray_bicubic(sampler2DArray tex, vec3 uv, vec2 texture_size) {
+	vec2 texel_size = vec2(1.0) / texture_size;
+
+	uv.xy = uv.xy * texture_size + vec2(0.5);
+
+	vec2 iuv = floor(uv.xy);
+	vec2 fuv = fract(uv.xy);
+
+	float g0x = g0(fuv.x);
+	float g1x = g1(fuv.x);
+	float h0x = h0(fuv.x);
+	float h1x = h1(fuv.x);
+	float h0y = h0(fuv.y);
+	float h1y = h1(fuv.y);
+
+	vec2 p0 = (vec2(iuv.x + h0x, iuv.y + h0y) - vec2(0.5)) * texel_size;
+	vec2 p1 = (vec2(iuv.x + h1x, iuv.y + h0y) - vec2(0.5)) * texel_size;
+	vec2 p2 = (vec2(iuv.x + h0x, iuv.y + h1y) - vec2(0.5)) * texel_size;
+	vec2 p3 = (vec2(iuv.x + h1x, iuv.y + h1y) - vec2(0.5)) * texel_size;
+
+	return (g0(fuv.y) * (g0x * texture(tex, vec3(p0, uv.z)) + g1x * texture(tex, vec3(p1, uv.z)))) +
+			(g1(fuv.y) * (g0x * texture(tex, vec3(p2, uv.z)) + g1x * texture(tex, vec3(p3, uv.z))));
+}
+#endif //LIGHTMAP_BICUBIC_FILTER
+
 void main() {
 	//lay out everything, whatever is unused is optimized away anyway
 	vec3 vertex = vertex_interp;
@@ -1732,10 +1798,18 @@ void main() {
 
 #ifdef USE_SH_LIGHTMAP
 		uvw.z *= 4.0; // SH textures use 4 times more data.
+
+#ifdef LIGHTMAP_BICUBIC_FILTER
+		vec3 lm_light_l0 = textureArray_bicubic(lightmap_textures, uvw + vec3(0.0, 0.0, 0.0), lightmap_texture_size).rgb;
+		vec3 lm_light_l1n1 = textureArray_bicubic(lightmap_textures, uvw + vec3(0.0, 0.0, 1.0), lightmap_texture_size).rgb;
+		vec3 lm_light_l1_0 = textureArray_bicubic(lightmap_textures, uvw + vec3(0.0, 0.0, 2.0), lightmap_texture_size).rgb;
+		vec3 lm_light_l1p1 = textureArray_bicubic(lightmap_textures, uvw + vec3(0.0, 0.0, 3.0), lightmap_texture_size).rgb;
+#else
 		vec3 lm_light_l0 = textureLod(lightmap_textures, uvw + vec3(0.0, 0.0, 0.0), 0.0).rgb;
 		vec3 lm_light_l1n1 = textureLod(lightmap_textures, uvw + vec3(0.0, 0.0, 1.0), 0.0).rgb;
 		vec3 lm_light_l1_0 = textureLod(lightmap_textures, uvw + vec3(0.0, 0.0, 2.0), 0.0).rgb;
 		vec3 lm_light_l1p1 = textureLod(lightmap_textures, uvw + vec3(0.0, 0.0, 3.0), 0.0).rgb;
+#endif
 
 		vec3 n = normalize(lightmap_normal_xform * normal);
 
@@ -1749,8 +1823,12 @@ void main() {
 			specular_light += lm_light_l1_0 * 0.32573 * r.z * lightmap_exposure_normalization;
 			specular_light += lm_light_l1p1 * 0.32573 * r.x * lightmap_exposure_normalization;
 		}
+#else
+#ifdef LIGHTMAP_BICUBIC_FILTER
+		ambient_light += textureArray_bicubic(lightmap_textures, uvw, lightmap_texture_size).rgb * lightmap_exposure_normalization;
 #else
 		ambient_light += textureLod(lightmap_textures, uvw, 0.0).rgb * lightmap_exposure_normalization;
+#endif
 #endif
 	}
 #endif // USE_LIGHTMAP

drivers/gles3/storage/light_storage.cpp

@@ -1046,6 +1046,9 @@ void LightStorage::lightmap_set_textures(RID p_lightmap, RID p_light, bool p_use
 	lightmap->light_texture = p_light;
 	lightmap->uses_spherical_harmonics = p_uses_spherical_haromics;
 
+	Vector3i light_texture_size = GLES3::TextureStorage::get_singleton()->texture_get_size(lightmap->light_texture);
+	lightmap->light_texture_size = Vector2i(light_texture_size.x, light_texture_size.y);
+
 	GLuint tex = GLES3::TextureStorage::get_singleton()->texture_get_texid(lightmap->light_texture);
 	glBindTexture(GL_TEXTURE_2D_ARRAY, tex);
 	glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

drivers/gles3/storage/light_storage.h

@@ -180,6 +180,7 @@ struct Lightmap {
 	bool interior = false;
 	AABB bounds = AABB(Vector3(), Vector3(1, 1, 1));
 	float baked_exposure = 1.0;
+	Vector2i light_texture_size;
 	int32_t array_index = -1; //unassigned
 	PackedVector3Array points;
 	PackedColorArray point_sh;

drivers/gles3/storage/texture_storage.cpp

@@ -1680,6 +1680,14 @@ uint32_t TextureStorage::texture_get_texid(RID p_texture) const {
 	return texture->tex_id;
 }
 
+Vector3i TextureStorage::texture_get_size(RID p_texture) const {
+	Texture *texture = texture_owner.get_or_null(p_texture);
+
+	ERR_FAIL_NULL_V(texture, Vector3i(0, 0, 0));
+
+	return Vector3i(texture->width, texture->height, texture->depth);
+}
+
 uint32_t TextureStorage::texture_get_width(RID p_texture) const {
 	Texture *texture = texture_owner.get_or_null(p_texture);
 

drivers/gles3/storage/texture_storage.h

@@ -553,6 +553,7 @@ public:
 	void texture_set_data(RID p_texture, const Ref<Image> &p_image, int p_layer = 0);
 	virtual Image::Format texture_get_format(RID p_texture) const override;
 	uint32_t texture_get_texid(RID p_texture) const;
+	Vector3i texture_get_size(RID p_texture) const;
 	uint32_t texture_get_width(RID p_texture) const;
 	uint32_t texture_get_height(RID p_texture) const;
 	uint32_t texture_get_depth(RID p_texture) const;

editor/editor_node.cpp

@@ -429,6 +429,7 @@ void EditorNode::_update_from_settings() {
 
 	RS::get_singleton()->decals_set_filter(RS::DecalFilter(int(GLOBAL_GET("rendering/textures/decals/filter"))));
 	RS::get_singleton()->light_projectors_set_filter(RS::LightProjectorFilter(int(GLOBAL_GET("rendering/textures/light_projectors/filter"))));
+	RS::get_singleton()->lightmaps_set_bicubic_filter(GLOBAL_GET("rendering/lightmapping/lightmap_gi/use_bicubic_filter"));
 
 	SceneTree *tree = get_tree();
 	tree->set_debug_collisions_color(GLOBAL_GET("debug/shapes/collision/shape_color"));

servers/rendering/dummy/rasterizer_scene_dummy.h

@@ -186,6 +186,7 @@ public:
 
 	virtual void decals_set_filter(RS::DecalFilter p_filter) override {}
 	virtual void light_projectors_set_filter(RS::LightProjectorFilter p_filter) override {}
+	virtual void lightmaps_set_bicubic_filter(bool p_enable) override {}
 
 	RasterizerSceneDummy() {}
 	~RasterizerSceneDummy() {}

servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp

@@ -1103,9 +1103,17 @@ void RenderForwardClustered::_setup_lightmaps(const RenderDataRD *p_render_data,
 
 		RID lightmap = light_storage->lightmap_instance_get_lightmap(p_lightmaps[i]);
 
+		// Transform (for directional lightmaps).
 		Basis to_lm = light_storage->lightmap_instance_get_transform(p_lightmaps[i]).basis.inverse() * p_cam_transform.basis;
 		to_lm = to_lm.inverse().transposed(); //will transform normals
 		RendererRD::MaterialStorage::store_transform_3x3(to_lm, scene_state.lightmaps[i].normal_xform);
+
+		// Light texture size.
+		Vector2i lightmap_size = light_storage->lightmap_get_light_texture_size(lightmap);
+		scene_state.lightmaps[i].texture_size[0] = lightmap_size[0];
+		scene_state.lightmaps[i].texture_size[1] = lightmap_size[1];
+
+		// Exposure.
 		scene_state.lightmaps[i].exposure_normalization = 1.0;
 		if (p_render_data->camera_attributes.is_valid()) {
 			float baked_exposure = light_storage->lightmap_get_baked_exposure_normalization(lightmap);
@@ -4242,6 +4250,11 @@ void RenderForwardClustered::_update_shader_quality_settings() {
 
 	spec_constants.push_back(sc);
 
+	sc.constant_id = SPEC_CONSTANT_USE_LIGHTMAP_BICUBIC_FILTER;
+	sc.bool_value = lightmap_filter_bicubic_get();
+
+	spec_constants.push_back(sc);
+
 	scene_shader.set_default_specialization_constants(spec_constants);
 
 	base_uniforms_changed(); //also need this

servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.h

@@ -73,6 +73,7 @@ class RenderForwardClustered : public RendererSceneRenderRD {
 		SPEC_CONSTANT_DECAL_FILTER = 10,
 		SPEC_CONSTANT_PROJECTOR_FILTER = 11,
 		SPEC_CONSTANT_USE_DEPTH_FOG = 12,
+		SPEC_CONSTANT_USE_LIGHTMAP_BICUBIC_FILTER = 13,
 	};
 
 	enum {
@@ -235,8 +236,9 @@ class RenderForwardClustered : public RendererSceneRenderRD {
 
 	struct LightmapData {
 		float normal_xform[12];
-		float pad[3];
+		float texture_size[2];
 		float exposure_normalization;
+		float pad;
 	};
 
 	struct LightmapCaptureData {

servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp

@@ -563,9 +563,17 @@ void RenderForwardMobile::_setup_lightmaps(const RenderDataRD *p_render_data, co
 
 		RID lightmap = light_storage->lightmap_instance_get_lightmap(p_lightmaps[i]);
 
+		// Transform (for directional lightmaps).
 		Basis to_lm = light_storage->lightmap_instance_get_transform(p_lightmaps[i]).basis.inverse() * p_cam_transform.basis;
 		to_lm = to_lm.inverse().transposed(); //will transform normals
 		RendererRD::MaterialStorage::store_transform_3x3(to_lm, scene_state.lightmaps[i].normal_xform);
+
+		// Light texture size.
+		Vector2i lightmap_size = light_storage->lightmap_get_light_texture_size(lightmap);
+		scene_state.lightmaps[i].texture_size[0] = lightmap_size[0];
+		scene_state.lightmaps[i].texture_size[1] = lightmap_size[1];
+
+		// Exposure.
 		scene_state.lightmaps[i].exposure_normalization = 1.0;
 		if (p_render_data->camera_attributes.is_valid()) {
 			float baked_exposure = light_storage->lightmap_get_baked_exposure_normalization(lightmap);
@@ -2781,6 +2789,11 @@ void RenderForwardMobile::_update_shader_quality_settings() {
 
 	spec_constants.push_back(sc);
 
+	sc.constant_id = SPEC_CONSTANT_USE_LIGHTMAP_BICUBIC_FILTER;
+	sc.bool_value = lightmap_filter_bicubic_get();
+
+	spec_constants.push_back(sc);
+
 	scene_shader.set_default_specialization_constants(spec_constants);
 
 	base_uniforms_changed(); //also need this

servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.h

@@ -82,7 +82,7 @@ private:
 		SPEC_CONSTANT_DISABLE_FOG = 14,
 		SPEC_CONSTANT_USE_DEPTH_FOG = 16,
 		SPEC_CONSTANT_IS_MULTIMESH = 17,
-
+		SPEC_CONSTANT_USE_LIGHTMAP_BICUBIC_FILTER = 18,
 	};
 
 	enum {
@@ -208,8 +208,9 @@ private:
 
 	struct LightmapData {
 		float normal_xform[12];
-		float pad[3];
+		float texture_size[2];
 		float exposure_normalization;
+		float pad;
 	};
 
 	struct LightmapCaptureData {

servers/rendering/renderer_rd/renderer_scene_render_rd.cpp

@@ -1040,6 +1040,14 @@ void RendererSceneRenderRD::light_projectors_set_filter(RenderingServer::LightPr
 	_update_shader_quality_settings();
 }
 
+void RendererSceneRenderRD::lightmaps_set_bicubic_filter(bool p_enable) {
+	if (lightmap_filter_bicubic == p_enable) {
+		return;
+	}
+	lightmap_filter_bicubic = p_enable;
+	_update_shader_quality_settings();
+}
+
 int RendererSceneRenderRD::get_roughness_layers() const {
 	return sky.roughness_layers;
 }
@@ -1483,6 +1491,7 @@ void RendererSceneRenderRD::init() {
 
 	decals_set_filter(RS::DecalFilter(int(GLOBAL_GET("rendering/textures/decals/filter"))));
 	light_projectors_set_filter(RS::LightProjectorFilter(int(GLOBAL_GET("rendering/textures/light_projectors/filter"))));
+	lightmaps_set_bicubic_filter(GLOBAL_GET("rendering/lightmapping/lightmap_gi/use_bicubic_filter"));
 
 	cull_argument.set_page_pool(&cull_argument_pool);
 

servers/rendering/renderer_rd/renderer_scene_render_rd.h

@@ -133,6 +133,7 @@ private:
 	float *directional_soft_shadow_kernel = nullptr;
 	float *penumbra_shadow_kernel = nullptr;
 	float *soft_shadow_kernel = nullptr;
+	bool lightmap_filter_bicubic = false;
 	int directional_penumbra_shadow_samples = 0;
 	int directional_soft_shadow_samples = 0;
 	int penumbra_shadow_samples = 0;
@@ -262,6 +263,7 @@ public:
 
 	virtual void decals_set_filter(RS::DecalFilter p_filter) override;
 	virtual void light_projectors_set_filter(RS::LightProjectorFilter p_filter) override;
+	virtual void lightmaps_set_bicubic_filter(bool p_enable) override;
 
 	_FORCE_INLINE_ RS::ShadowQuality shadows_quality_get() const {
 		return shadows_quality;
@@ -292,6 +294,9 @@ public:
 	_FORCE_INLINE_ int directional_penumbra_shadow_samples_get() const {
 		return directional_penumbra_shadow_samples;
 	}
+	_FORCE_INLINE_ bool lightmap_filter_bicubic_get() const {
+		return lightmap_filter_bicubic;
+	}
 	_FORCE_INLINE_ int directional_soft_shadow_samples_get() const {
 		return directional_soft_shadow_samples;
 	}

servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered.glsl

@@ -657,6 +657,7 @@ layout(constant_id = 9) const uint sc_directional_penumbra_shadow_samples = 4;
 layout(constant_id = 10) const bool sc_decal_use_mipmaps = true;
 layout(constant_id = 11) const bool sc_projector_use_mipmaps = true;
 layout(constant_id = 12) const bool sc_use_depth_fog = false;
+layout(constant_id = 13) const bool sc_use_lightmap_bicubic_filter = false;
 
 // not used in clustered renderer but we share some code with the mobile renderer that requires this.
 const float sc_luminance_multiplier = 1.0;
@@ -701,6 +702,67 @@ layout(location = 9) in float dp_clip;
 
 layout(location = 10) in flat uint instance_index_interp;
 
+#ifdef USE_LIGHTMAP
+// w0, w1, w2, and w3 are the four cubic B-spline basis functions
+float w0(float a) {
+	return (1.0 / 6.0) * (a * (a * (-a + 3.0) - 3.0) + 1.0);
+}
+
+float w1(float a) {
+	return (1.0 / 6.0) * (a * a * (3.0 * a - 6.0) + 4.0);
+}
+
+float w2(float a) {
+	return (1.0 / 6.0) * (a * (a * (-3.0 * a + 3.0) + 3.0) + 1.0);
+}
+
+float w3(float a) {
+	return (1.0 / 6.0) * (a * a * a);
+}
+
+// g0 and g1 are the two amplitude functions
+float g0(float a) {
+	return w0(a) + w1(a);
+}
+
+float g1(float a) {
+	return w2(a) + w3(a);
+}
+
+// h0 and h1 are the two offset functions
+float h0(float a) {
+	return -1.0 + w1(a) / (w0(a) + w1(a));
+}
+
+float h1(float a) {
+	return 1.0 + w3(a) / (w2(a) + w3(a));
+}
+
+vec4 textureArray_bicubic(texture2DArray tex, vec3 uv, vec2 texture_size) {
+	vec2 texel_size = vec2(1.0) / texture_size;
+
+	uv.xy = uv.xy * texture_size + vec2(0.5);
+
+	vec2 iuv = floor(uv.xy);
+	vec2 fuv = fract(uv.xy);
+
+	float g0x = g0(fuv.x);
+	float g1x = g1(fuv.x);
+	float h0x = h0(fuv.x);
+	float h1x = h1(fuv.x);
+	float h0y = h0(fuv.y);
+	float h1y = h1(fuv.y);
+
+	vec2 p0 = (vec2(iuv.x + h0x, iuv.y + h0y) - vec2(0.5)) * texel_size;
+	vec2 p1 = (vec2(iuv.x + h1x, iuv.y + h0y) - vec2(0.5)) * texel_size;
+	vec2 p2 = (vec2(iuv.x + h0x, iuv.y + h1y) - vec2(0.5)) * texel_size;
+	vec2 p3 = (vec2(iuv.x + h1x, iuv.y + h1y) - vec2(0.5)) * texel_size;
+
+	return (g0(fuv.y) * (g0x * texture(sampler2DArray(tex, SAMPLER_LINEAR_CLAMP), vec3(p0, uv.z)) + g1x * texture(sampler2DArray(tex, SAMPLER_LINEAR_CLAMP), vec3(p1, uv.z)))) +
+			(g1(fuv.y) * (g0x * texture(sampler2DArray(tex, SAMPLER_LINEAR_CLAMP), vec3(p2, uv.z)) + g1x * texture(sampler2DArray(tex, SAMPLER_LINEAR_CLAMP), vec3(p3, uv.z))));
+}
+#endif //USE_LIGHTMAP
+
 #ifdef USE_MULTIVIEW
 #ifdef has_VK_KHR_multiview
 #define ViewIndex gl_ViewIndex
@@ -1449,10 +1511,23 @@ void fragment_shader(in SceneData scene_data) {
 
 		if (uses_sh) {
 			uvw.z *= 4.0; //SH textures use 4 times more data
-			vec3 lm_light_l0 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 0.0), 0.0).rgb;
-			vec3 lm_light_l1n1 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 1.0), 0.0).rgb;
-			vec3 lm_light_l1_0 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 2.0), 0.0).rgb;
-			vec3 lm_light_l1p1 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 3.0), 0.0).rgb;
+
+			vec3 lm_light_l0;
+			vec3 lm_light_l1n1;
+			vec3 lm_light_l1_0;
+			vec3 lm_light_l1p1;
+
+			if (sc_use_lightmap_bicubic_filter) {
+				lm_light_l0 = textureArray_bicubic(lightmap_textures[ofs], uvw + vec3(0.0, 0.0, 0.0), lightmaps.data[ofs].light_texture_size).rgb;
+				lm_light_l1n1 = textureArray_bicubic(lightmap_textures[ofs], uvw + vec3(0.0, 0.0, 1.0), lightmaps.data[ofs].light_texture_size).rgb;
+				lm_light_l1_0 = textureArray_bicubic(lightmap_textures[ofs], uvw + vec3(0.0, 0.0, 2.0), lightmaps.data[ofs].light_texture_size).rgb;
+				lm_light_l1p1 = textureArray_bicubic(lightmap_textures[ofs], uvw + vec3(0.0, 0.0, 3.0), lightmaps.data[ofs].light_texture_size).rgb;
+			} else {
+				lm_light_l0 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 0.0), 0.0).rgb;
+				lm_light_l1n1 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 1.0), 0.0).rgb;
+				lm_light_l1_0 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 2.0), 0.0).rgb;
+				lm_light_l1p1 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 3.0), 0.0).rgb;
+			}
 
 			vec3 n = normalize(lightmaps.data[ofs].normal_xform * normal);
 			float en = lightmaps.data[ofs].exposure_normalization;
@@ -1469,7 +1544,11 @@ void fragment_shader(in SceneData scene_data) {
 			}
 
 		} else {
-			ambient_light += textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw, 0.0).rgb * lightmaps.data[ofs].exposure_normalization;
+			if (sc_use_lightmap_bicubic_filter) {
+				ambient_light += textureArray_bicubic(lightmap_textures[ofs], uvw, lightmaps.data[ofs].light_texture_size).rgb * lightmaps.data[ofs].exposure_normalization;
+			} else {
+				ambient_light += textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw, 0.0).rgb * lightmaps.data[ofs].exposure_normalization;
+			}
 		}
 	}
 #else

servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered_inc.glsl

@@ -94,8 +94,9 @@ directional_lights;
 
 struct Lightmap {
 	mat3 normal_xform;
-	vec3 pad;
+	vec2 light_texture_size;
 	float exposure_normalization;
+	vec2 pad;
 };
 
 layout(set = 0, binding = 7, std140) restrict readonly buffer Lightmaps {

servers/rendering/renderer_rd/shaders/forward_mobile/scene_forward_mobile.glsl

@@ -521,6 +521,7 @@ layout(constant_id = 9) const bool sc_disable_omni_lights = false;
 layout(constant_id = 10) const bool sc_disable_spot_lights = false;
 layout(constant_id = 11) const bool sc_disable_reflection_probes = false;
 layout(constant_id = 12) const bool sc_disable_directional_lights = false;
+layout(constant_id = 18) const bool sc_use_lightmap_bicubic_filter = false;
 
 #endif //!MODE_UNSHADED
 
@@ -567,6 +568,67 @@ layout(location = 9) highp in float dp_clip;
 
 #endif
 
+#ifdef USE_LIGHTMAP
+// w0, w1, w2, and w3 are the four cubic B-spline basis functions
+float w0(float a) {
+	return (1.0 / 6.0) * (a * (a * (-a + 3.0) - 3.0) + 1.0);
+}
+
+float w1(float a) {
+	return (1.0 / 6.0) * (a * a * (3.0 * a - 6.0) + 4.0);
+}
+
+float w2(float a) {
+	return (1.0 / 6.0) * (a * (a * (-3.0 * a + 3.0) + 3.0) + 1.0);
+}
+
+float w3(float a) {
+	return (1.0 / 6.0) * (a * a * a);
+}
+
+// g0 and g1 are the two amplitude functions
+float g0(float a) {
+	return w0(a) + w1(a);
+}
+
+float g1(float a) {
+	return w2(a) + w3(a);
+}
+
+// h0 and h1 are the two offset functions
+float h0(float a) {
+	return -1.0 + w1(a) / (w0(a) + w1(a));
+}
+
+float h1(float a) {
+	return 1.0 + w3(a) / (w2(a) + w3(a));
+}
+
+vec4 textureArray_bicubic(texture2DArray tex, vec3 uv, vec2 texture_size) {
+	vec2 texel_size = vec2(1.0) / texture_size;
+
+	uv.xy = uv.xy * texture_size + vec2(0.5);
+
+	vec2 iuv = floor(uv.xy);
+	vec2 fuv = fract(uv.xy);
+
+	float g0x = g0(fuv.x);
+	float g1x = g1(fuv.x);
+	float h0x = h0(fuv.x);
+	float h1x = h1(fuv.x);
+	float h0y = h0(fuv.y);
+	float h1y = h1(fuv.y);
+
+	vec2 p0 = (vec2(iuv.x + h0x, iuv.y + h0y) - vec2(0.5)) * texel_size;
+	vec2 p1 = (vec2(iuv.x + h1x, iuv.y + h0y) - vec2(0.5)) * texel_size;
+	vec2 p2 = (vec2(iuv.x + h0x, iuv.y + h1y) - vec2(0.5)) * texel_size;
+	vec2 p3 = (vec2(iuv.x + h1x, iuv.y + h1y) - vec2(0.5)) * texel_size;
+
+	return (g0(fuv.y) * (g0x * texture(sampler2DArray(tex, SAMPLER_LINEAR_CLAMP), vec3(p0, uv.z)) + g1x * texture(sampler2DArray(tex, SAMPLER_LINEAR_CLAMP), vec3(p1, uv.z)))) +
+			(g1(fuv.y) * (g0x * texture(sampler2DArray(tex, SAMPLER_LINEAR_CLAMP), vec3(p2, uv.z)) + g1x * texture(sampler2DArray(tex, SAMPLER_LINEAR_CLAMP), vec3(p3, uv.z))));
+}
+#endif //USE_LIGHTMAP
+
 #ifdef USE_MULTIVIEW
 #ifdef has_VK_KHR_multiview
 #define ViewIndex gl_ViewIndex
@@ -1209,10 +1271,22 @@ void main() {
 
 		if (uses_sh) {
 			uvw.z *= 4.0; //SH textures use 4 times more data
-			vec3 lm_light_l0 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 0.0), 0.0).rgb;
-			vec3 lm_light_l1n1 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 1.0), 0.0).rgb;
-			vec3 lm_light_l1_0 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 2.0), 0.0).rgb;
-			vec3 lm_light_l1p1 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 3.0), 0.0).rgb;
+			vec3 lm_light_l0;
+			vec3 lm_light_l1n1;
+			vec3 lm_light_l1_0;
+			vec3 lm_light_l1p1;
+
+			if (sc_use_lightmap_bicubic_filter) {
+				lm_light_l0 = textureArray_bicubic(lightmap_textures[ofs], uvw + vec3(0.0, 0.0, 0.0), lightmaps.data[ofs].light_texture_size).rgb;
+				lm_light_l1n1 = textureArray_bicubic(lightmap_textures[ofs], uvw + vec3(0.0, 0.0, 1.0), lightmaps.data[ofs].light_texture_size).rgb;
+				lm_light_l1_0 = textureArray_bicubic(lightmap_textures[ofs], uvw + vec3(0.0, 0.0, 2.0), lightmaps.data[ofs].light_texture_size).rgb;
+				lm_light_l1p1 = textureArray_bicubic(lightmap_textures[ofs], uvw + vec3(0.0, 0.0, 3.0), lightmaps.data[ofs].light_texture_size).rgb;
+			} else {
+				lm_light_l0 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 0.0), 0.0).rgb;
+				lm_light_l1n1 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 1.0), 0.0).rgb;
+				lm_light_l1_0 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 2.0), 0.0).rgb;
+				lm_light_l1p1 = textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw + vec3(0.0, 0.0, 3.0), 0.0).rgb;
+			}
 
 			vec3 n = normalize(lightmaps.data[ofs].normal_xform * normal);
 			float exposure_normalization = lightmaps.data[ofs].exposure_normalization;
@@ -1229,7 +1303,11 @@ void main() {
 			}
 
 		} else {
-			ambient_light += textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw, 0.0).rgb * lightmaps.data[ofs].exposure_normalization;
+			if (sc_use_lightmap_bicubic_filter) {
+				ambient_light += textureArray_bicubic(lightmap_textures[ofs], uvw, lightmaps.data[ofs].light_texture_size).rgb * lightmaps.data[ofs].exposure_normalization;
+			} else {
+				ambient_light += textureLod(sampler2DArray(lightmap_textures[ofs], SAMPLER_LINEAR_CLAMP), uvw, 0.0).rgb * lightmaps.data[ofs].exposure_normalization;
+			}
 		}
 	}
 

servers/rendering/renderer_rd/shaders/forward_mobile/scene_forward_mobile_inc.glsl

@@ -71,8 +71,9 @@ directional_lights;
 
 struct Lightmap {
 	mediump mat3 normal_xform;
-	vec3 pad;
+	vec2 light_texture_size;
 	float exposure_normalization;
+	float pad;
 };
 
 layout(set = 0, binding = 7, std140) restrict readonly buffer Lightmaps {

servers/rendering/renderer_rd/storage_rd/light_storage.cpp

@@ -1813,6 +1813,7 @@ void LightStorage::lightmap_set_textures(RID p_lightmap, RID p_light, bool p_use
 	}
 
 	t->lightmap_users.insert(p_lightmap);
+	lm->light_texture_size = Vector2i(t->width, t->height);
 
 	if (using_lightmap_array) {
 		if (lm->array_index < 0) {

servers/rendering/renderer_rd/storage_rd/light_storage.h

@@ -332,6 +332,7 @@ private:
 		bool interior = false;
 		AABB bounds = AABB(Vector3(), Vector3(1, 1, 1));
 		float baked_exposure = 1.0;
+		Vector2i light_texture_size;
 		int32_t array_index = -1; //unassigned
 		PackedVector3Array points;
 		PackedColorArray point_sh;
@@ -985,6 +986,10 @@ public:
 		const Lightmap *lm = lightmap_owner.get_or_null(p_lightmap);
 		return lm->uses_spherical_harmonics;
 	}
+	_FORCE_INLINE_ Vector2i lightmap_get_light_texture_size(RID p_lightmap) const {
+		const Lightmap *lm = lightmap_owner.get_or_null(p_lightmap);
+		return lm->light_texture_size;
+	}
 	_FORCE_INLINE_ uint64_t lightmap_array_get_version() const {
 		ERR_FAIL_COND_V(!using_lightmap_array, 0); //only for arrays
 		return lightmap_array_version;

servers/rendering/renderer_rd/storage_rd/render_data_rd.h

@@ -73,6 +73,8 @@ public:
 	uint32_t directional_light_count = 0;
 	bool directional_light_soft_shadows = false;
 
+	bool lightmap_bicubic_filter = false;
+
 	RenderingMethod::RenderInfo *render_info = nullptr;
 
 	/* Viewport data */

servers/rendering/renderer_scene_cull.h

@@ -1418,6 +1418,7 @@ public:
 
 	PASS1(decals_set_filter, RS::DecalFilter)
 	PASS1(light_projectors_set_filter, RS::LightProjectorFilter)
+	PASS1(lightmaps_set_bicubic_filter, bool)
 
 	virtual void update();
 

servers/rendering/renderer_scene_render.h

@@ -338,6 +338,7 @@ public:
 
 	virtual void decals_set_filter(RS::DecalFilter p_filter) = 0;
 	virtual void light_projectors_set_filter(RS::LightProjectorFilter p_filter) = 0;
+	virtual void lightmaps_set_bicubic_filter(bool p_enable) = 0;
 
 	virtual void update() = 0;
 	virtual ~RendererSceneRender() {}

servers/rendering/rendering_method.h

@@ -349,6 +349,7 @@ public:
 
 	virtual void decals_set_filter(RS::DecalFilter p_filter) = 0;
 	virtual void light_projectors_set_filter(RS::LightProjectorFilter p_filter) = 0;
+	virtual void lightmaps_set_bicubic_filter(bool p_enable) = 0;
 
 	virtual bool free(RID p_rid) = 0;
 

servers/rendering/rendering_server_default.h

@@ -762,6 +762,7 @@ public:
 	FUNC1(directional_soft_shadow_filter_set_quality, ShadowQuality);
 	FUNC1(decals_set_filter, RS::DecalFilter);
 	FUNC1(light_projectors_set_filter, RS::LightProjectorFilter);
+	FUNC1(lightmaps_set_bicubic_filter, bool);
 
 	/* CAMERA ATTRIBUTES */
 

servers/rendering_server.cpp

@@ -2477,6 +2477,7 @@ void RenderingServer::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("light_directional_set_sky_mode", "light", "mode"), &RenderingServer::light_directional_set_sky_mode);
 
 	ClassDB::bind_method(D_METHOD("light_projectors_set_filter", "filter"), &RenderingServer::light_projectors_set_filter);
+	ClassDB::bind_method(D_METHOD("lightmaps_set_bicubic_filter", "enable"), &RenderingServer::lightmaps_set_bicubic_filter);
 
 	BIND_ENUM_CONSTANT(LIGHT_PROJECTOR_FILTER_NEAREST);
 	BIND_ENUM_CONSTANT(LIGHT_PROJECTOR_FILTER_LINEAR);
@@ -3618,6 +3619,7 @@ void RenderingServer::init() {
 
 	GLOBAL_DEF(PropertyInfo(Variant::FLOAT, "rendering/lightmapping/probe_capture/update_speed", PROPERTY_HINT_RANGE, "0.001,256,0.001"), 15);
 	GLOBAL_DEF(PropertyInfo(Variant::FLOAT, "rendering/lightmapping/primitive_meshes/texel_size", PROPERTY_HINT_RANGE, "0.001,100,0.001"), 0.2);
+	GLOBAL_DEF("rendering/lightmapping/lightmap_gi/use_bicubic_filter", true);
 
 	GLOBAL_DEF(PropertyInfo(Variant::INT, "rendering/global_illumination/sdfgi/probe_ray_count", PROPERTY_HINT_ENUM, "8 (Fastest),16,32,64,96,128 (Slowest)"), 1);
 	GLOBAL_DEF(PropertyInfo(Variant::INT, "rendering/global_illumination/sdfgi/frames_to_converge", PROPERTY_HINT_ENUM, "5 (Less Latency but Lower Quality),10,15,20,25,30 (More Latency but Higher Quality)"), 5);

servers/rendering_server.h

@@ -687,6 +687,8 @@ public:
 
 	virtual void lightmap_set_probe_capture_update_speed(float p_speed) = 0;
 
+	virtual void lightmaps_set_bicubic_filter(bool p_enable) = 0;
+
 	/* PARTICLES API */
 
 	virtual RID particles_create() = 0;