Fix sky rendering with multiview in OpenGL

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -731,6 +731,11 @@ void RasterizerSceneGLES3::_setup_sky(const RenderDataGLES3 *p_render_data, cons
 			}
 		}
 
+		if (p_render_data->view_count > 1) {
+			glBindBufferBase(GL_UNIFORM_BUFFER, SKY_MULTIVIEW_UNIFORM_LOCATION, scene_state.multiview_buffer);
+			glBindBuffer(GL_UNIFORM_BUFFER, 0);
+		}
+
 		if (!sky->radiance) {
 			_invalidate_sky(sky);
 			_update_dirty_skys();
@@ -738,7 +743,7 @@ void RasterizerSceneGLES3::_setup_sky(const RenderDataGLES3 *p_render_data, cons
 	}
 }
 
-void RasterizerSceneGLES3::_draw_sky(RID p_env, const Projection &p_projection, const Transform3D &p_transform, float p_luminance_multiplier) {
+void RasterizerSceneGLES3::_draw_sky(RID p_env, const Projection &p_projection, const Transform3D &p_transform, float p_luminance_multiplier, bool p_use_multiview, bool p_flip_y) {
 	GLES3::MaterialStorage *material_storage = GLES3::MaterialStorage::get_singleton();
 	ERR_FAIL_COND(p_env.is_null());
 
@@ -748,6 +753,11 @@ void RasterizerSceneGLES3::_draw_sky(RID p_env, const Projection &p_projection,
 	GLES3::SkyMaterialData *material_data = nullptr;
 	RID sky_material;
 
+	uint64_t spec_constants = p_use_multiview ? SkyShaderGLES3::USE_MULTIVIEW : 0;
+	if (p_flip_y) {
+		spec_constants |= SkyShaderGLES3::USE_INVERTED_Y;
+	}
+
 	RS::EnvironmentBG background = environment_get_background(p_env);
 
 	if (sky) {
@@ -792,16 +802,21 @@ void RasterizerSceneGLES3::_draw_sky(RID p_env, const Projection &p_projection,
 	sky_transform.invert();
 	sky_transform = sky_transform * p_transform.basis;
 
-	bool success = material_storage->shaders.sky_shader.version_bind_shader(shader_data->version, SkyShaderGLES3::MODE_BACKGROUND);
+	bool success = material_storage->shaders.sky_shader.version_bind_shader(shader_data->version, SkyShaderGLES3::MODE_BACKGROUND, spec_constants);
 	if (!success) {
 		return;
 	}
 
-	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::ORIENTATION, sky_transform, shader_data->version, SkyShaderGLES3::MODE_BACKGROUND);
-	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::PROJECTION, camera.columns[2][0], camera.columns[0][0], camera.columns[2][1], camera.columns[1][1], shader_data->version, SkyShaderGLES3::MODE_BACKGROUND);
-	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::POSITION, p_transform.origin, shader_data->version, SkyShaderGLES3::MODE_BACKGROUND);
-	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::TIME, time, shader_data->version, SkyShaderGLES3::MODE_BACKGROUND);
-	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::LUMINANCE_MULTIPLIER, p_luminance_multiplier, shader_data->version, SkyShaderGLES3::MODE_BACKGROUND);
+	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::ORIENTATION, sky_transform, shader_data->version, SkyShaderGLES3::MODE_BACKGROUND, spec_constants);
+	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::PROJECTION, camera.columns[2][0], camera.columns[0][0], camera.columns[2][1], camera.columns[1][1], shader_data->version, SkyShaderGLES3::MODE_BACKGROUND, spec_constants);
+	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::POSITION, p_transform.origin, shader_data->version, SkyShaderGLES3::MODE_BACKGROUND, spec_constants);
+	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::TIME, time, shader_data->version, SkyShaderGLES3::MODE_BACKGROUND, spec_constants);
+	material_storage->shaders.sky_shader.version_set_uniform(SkyShaderGLES3::LUMINANCE_MULTIPLIER, p_luminance_multiplier, shader_data->version, SkyShaderGLES3::MODE_BACKGROUND, spec_constants);
+
+	if (p_use_multiview) {
+		glBindBufferBase(GL_UNIFORM_BUFFER, SKY_MULTIVIEW_UNIFORM_LOCATION, scene_state.multiview_buffer);
+		glBindBuffer(GL_UNIFORM_BUFFER, 0);
+	}
 
 	glBindVertexArray(sky_globals.screen_triangle_array);
 	glDrawArrays(GL_TRIANGLES, 0, 3);
@@ -1975,7 +1990,7 @@ void RasterizerSceneGLES3::render_scene(const Ref<RenderSceneBuffers> &p_render_
 		scene_state.current_depth_draw = GLES3::SceneShaderData::DEPTH_DRAW_DISABLED;
 		scene_state.cull_mode = GLES3::SceneShaderData::CULL_BACK;
 
-		_draw_sky(render_data.environment, render_data.cam_projection, render_data.cam_transform, sky_energy_multiplier);
+		_draw_sky(render_data.environment, render_data.cam_projection, render_data.cam_transform, sky_energy_multiplier, p_camera_data->view_count > 1, flip_y);
 	}
 
 	RENDER_TIMESTAMP("Render 3D Transparent Pass");

drivers/gles3/rasterizer_scene_gles3.h

@@ -83,6 +83,7 @@ enum SkyUniformLocation {
 	SKY_EMPTY, // Unused, put here to avoid conflicts with SCENE_DATA_UNIFORM_LOCATION.
 	SKY_MATERIAL_UNIFORM_LOCATION,
 	SKY_DIRECTIONAL_LIGHT_UNIFORM_LOCATION,
+	SKY_MULTIVIEW_UNIFORM_LOCATION,
 };
 
 struct RenderDataGLES3 {
@@ -570,7 +571,7 @@ protected:
 	void _update_dirty_skys();
 	void _update_sky_radiance(RID p_env, const Projection &p_projection, const Transform3D &p_transform, float p_luminance_multiplier);
 	void _filter_sky_radiance(Sky *p_sky, int p_base_layer);
-	void _draw_sky(RID p_env, const Projection &p_projection, const Transform3D &p_transform, float p_luminance_multiplier);
+	void _draw_sky(RID p_env, const Projection &p_projection, const Transform3D &p_transform, float p_luminance_multiplier, bool p_use_multiview, bool p_flip_y);
 	void _free_sky_data(Sky *p_sky);
 
 public:

drivers/gles3/shaders/sky.glsl

@@ -10,6 +10,9 @@ mode_cubemap_quarter_res = #define USE_CUBEMAP_PASS \n#define USE_QUARTER_RES_PA
 
 #[specializations]
 
+USE_MULTIVIEW = false
+USE_INVERTED_Y = true
+
 #[vertex]
 
 layout(location = 0) in vec2 vertex_attrib;
@@ -19,7 +22,11 @@ out vec2 uv_interp;
 
 void main() {
 	uv_interp = vertex_attrib;
+#ifdef USE_INVERTED_Y
 	gl_Position = vec4(uv_interp, 1.0, 1.0);
+#else
+	gl_Position = vec4(uv_interp.x, uv_interp.y * -1.0, 1.0, 1.0);
+#endif
 }
 
 /* clang-format off */
@@ -37,6 +44,9 @@ uniform samplerCube radiance; //texunit:-1
 #ifdef USE_CUBEMAP_PASS
 uniform samplerCube half_res; //texunit:-2
 uniform samplerCube quarter_res; //texunit:-3
+#elif defined(USE_MULTIVIEW)
+uniform sampler2DArray half_res; //texunit:-2
+uniform sampler2DArray quarter_res; //texunit:-3
 #else
 uniform sampler2D half_res; //texunit:-2
 uniform sampler2D quarter_res; //texunit:-3
@@ -102,6 +112,15 @@ uniform float fog_density;
 uniform float z_far;
 uniform uint directional_light_count;
 
+#ifdef USE_MULTIVIEW
+layout(std140) uniform MultiviewData { // ubo:5
+	highp mat4 projection_matrix_view[MAX_VIEWS];
+	highp mat4 inv_projection_matrix_view[MAX_VIEWS];
+	highp vec4 eye_offset[MAX_VIEWS];
+}
+multiview_data;
+#endif
+
 layout(location = 0) out vec4 frag_color;
 
 #ifdef USE_DEBANDING
@@ -115,9 +134,20 @@ vec3 interleaved_gradient_noise(vec2 pos) {
 
 void main() {
 	vec3 cube_normal;
+#ifdef USE_MULTIVIEW
+	// In multiview our projection matrices will contain positional and rotational offsets that we need to properly unproject.
+	vec4 unproject = vec4(uv_interp.x, uv_interp.y, 1.0, 1.0);
+	vec4 unprojected = multiview_data.inv_projection_matrix_view[ViewIndex] * unproject;
+	cube_normal = unprojected.xyz / unprojected.w;
+	cube_normal += multiview_data.eye_offset[ViewIndex].xyz;
+#else
 	cube_normal.z = -1.0;
 	cube_normal.x = (uv_interp.x + projection.x) / projection.y;
 	cube_normal.y = (-uv_interp.y - projection.z) / projection.w;
+#endif
+#ifndef USE_INVERTED_Y
+	cube_normal.y *= -1.0;
+#endif
 	cube_normal = mat3(orientation) * cube_normal;
 	cube_normal = normalize(cube_normal);
 
@@ -146,11 +176,19 @@ void main() {
 #endif
 #else
 #ifdef USES_HALF_RES_COLOR
+#ifdef USE_MULTIVIEW
+	half_res_color = textureLod(sampler2DArray(half_res, material_samplers[SAMPLER_LINEAR_CLAMP]), vec3(uv, ViewIndex), 0.0);
+#else
 	half_res_color = textureLod(sampler2D(half_res, material_samplers[SAMPLER_LINEAR_CLAMP]), uv, 0.0);
 #endif
+#endif
 #ifdef USES_QUARTER_RES_COLOR
+#ifdef USE_MULTIVIEW
+	quarter_res_color = textureLod(sampler2DArray(quarter_res, material_samplers[SAMPLER_LINEAR_CLAMP]), vec3(uv, ViewIndex), 0.0);
+#else
 	quarter_res_color = textureLod(sampler2D(quarter_res, material_samplers[SAMPLER_LINEAR_CLAMP]), uv, 0.0);
 #endif
+#endif
 #endif
 
 	{