Fix Depth-Prepass transparency mode

Add mising bits of implementation and ensure depth-prepass objects are
only rendered in the transparency pass.

3 files changed, 23 insertions, 11 deletions

diff --git a/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp b/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp
index 22e3bbdb00..6d85c1f4c1 100644
--- a/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp
+++ b/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp
@@ -334,6 +334,10 @@ void RenderForwardClustered::_render_list_template(RenderingDevice::DrawListID p
 		const GeometryInstanceSurfaceDataCache *surf = p_params->elements[i];
 		const RenderElementInfo &element_info = p_params->element_info[i];
 
+		if ((p_pass_mode == PASS_MODE_COLOR || p_pass_mode == PASS_MODE_COLOR_SPECULAR) && !(surf->flags & GeometryInstanceSurfaceDataCache::FLAG_PASS_OPAQUE)) {
+			continue; // Objects with "Depth-prepass" transparency are included in both render lists, but should only be rendered in the transparent pass
+		}
+
 		if (surf->owner->instance_count == 0) {
 			continue;
 		}
@@ -958,20 +962,20 @@ void RenderForwardClustered::_fill_render_list(RenderListType p_render_list, con
 		bool uses_gi = false;
 		float fade_alpha = 1.0;
 
-		if (p_render_list == RENDER_LIST_OPAQUE) {
-			if (inst->fade_near || inst->fade_far) {
-				float fade_dist = inst->transform.origin.distance_to(p_render_data->cam_transform.origin);
-				if (inst->fade_far && fade_dist > inst->fade_far_begin) {
-					fade_alpha = MAX(0.0, 1.0 - (fade_dist - inst->fade_far_begin) / (inst->fade_far_end - inst->fade_far_begin));
-				} else if (inst->fade_near && fade_dist < inst->fade_near_end) {
-					fade_alpha = MAX(0.0, (fade_dist - inst->fade_near_begin) / (inst->fade_near_end - inst->fade_near_begin));
-				}
+		if (inst->fade_near || inst->fade_far) {
+			float fade_dist = inst->transform.origin.distance_to(p_render_data->cam_transform.origin);
+			if (inst->fade_far && fade_dist > inst->fade_far_begin) {
+				fade_alpha = MAX(0.0, 1.0 - (fade_dist - inst->fade_far_begin) / (inst->fade_far_end - inst->fade_far_begin));
+			} else if (inst->fade_near && fade_dist < inst->fade_near_end) {
+				fade_alpha = MAX(0.0, (fade_dist - inst->fade_near_begin) / (inst->fade_near_end - inst->fade_near_begin));
 			}
+		}
 
-			fade_alpha *= inst->force_alpha * inst->parent_fade_alpha;
+		fade_alpha *= inst->force_alpha * inst->parent_fade_alpha;
 
-			flags = (flags & ~INSTANCE_DATA_FLAGS_FADE_MASK) | (uint32_t(fade_alpha * 255.0) << INSTANCE_DATA_FLAGS_FADE_SHIFT);
+		flags = (flags & ~INSTANCE_DATA_FLAGS_FADE_MASK) | (uint32_t(fade_alpha * 255.0) << INSTANCE_DATA_FLAGS_FADE_SHIFT);
 
+		if (p_render_list == RENDER_LIST_OPAQUE) {
 			// Setup GI
 			if (inst->lightmap_instance.is_valid()) {
 				int32_t lightmap_cull_index = -1;
@@ -1206,6 +1210,7 @@ void RenderForwardClustered::_render_scene(RenderDataRD *p_render_data, const Co
 	scene_state.ubo.viewport_size[0] = vp_he.x;
 	scene_state.ubo.viewport_size[1] = vp_he.y;
 	scene_state.ubo.directional_light_count = 0;
+	scene_state.ubo.opaque_prepass_threshold = 0.99f;
 
 	Size2i screen_size;
 	RID opaque_framebuffer;
@@ -1449,6 +1454,7 @@ void RenderForwardClustered::_render_scene(RenderDataRD *p_render_data, const Co
 	RD::get_singleton()->draw_command_begin_label("Render Opaque Pass");
 
 	scene_state.ubo.directional_light_count = p_render_data->directional_light_count;
+	scene_state.ubo.opaque_prepass_threshold = 0.0f;
 
 	_setup_environment(p_render_data, p_render_data->reflection_probe.is_valid(), screen_size, !p_render_data->reflection_probe.is_valid(), p_default_bg_color, p_render_data->render_buffers.is_valid());
 
@@ -1632,6 +1638,7 @@ void RenderForwardClustered::_render_shadow_append(RID p_framebuffer, const Page
 	render_data.render_info = p_render_info;
 
 	scene_state.ubo.dual_paraboloid_side = p_use_dp_flip ? -1 : 1;
+	scene_state.ubo.opaque_prepass_threshold = 0.1f;
 
 	_setup_environment(&render_data, true, Vector2(1, 1), !p_flip_y, Color(), false, p_use_pancake, shadow_pass_index);
 
@@ -1718,6 +1725,7 @@ void RenderForwardClustered::_render_particle_collider_heightfield(RID p_fb, con
 
 	_update_render_base_uniform_set();
 	scene_state.ubo.dual_paraboloid_side = 0;
+	scene_state.ubo.opaque_prepass_threshold = 0.0;
 
 	_setup_environment(&render_data, true, Vector2(1, 1), true, Color(), false, false);
 
@@ -1755,6 +1763,7 @@ void RenderForwardClustered::_render_material(const Transform3D &p_cam_transform
 
 	scene_state.ubo.dual_paraboloid_side = 0;
 	scene_state.ubo.material_uv2_mode = false;
+	scene_state.ubo.opaque_prepass_threshold = 0.0f;
 
 	_setup_environment(&render_data, true, Vector2(1, 1), false, Color());
 
@@ -1798,6 +1807,7 @@ void RenderForwardClustered::_render_uv2(const PagedArray<GeometryInstance *> &p
 
 	scene_state.ubo.dual_paraboloid_side = 0;
 	scene_state.ubo.material_uv2_mode = true;
+	scene_state.ubo.opaque_prepass_threshold = 0.0;
 
 	_setup_environment(&render_data, true, Vector2(1, 1), false, Color());
 
diff --git a/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.h b/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.h
index 2ba9558128..7707d77296 100644
--- a/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.h
+++ b/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.h
@@ -257,7 +257,8 @@ class RenderForwardClustered : public RendererSceneRenderRD {
 
 			float roughness_limiter_amount;
 			float roughness_limiter_limit;
-			uint32_t roughness_limiter_pad[2];
+			float opaque_prepass_threshold;
+			uint32_t roughness_limiter_pad;
 
 			float sdf_to_bounds[16];
 
diff --git a/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp b/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp
index 61f2031a70..768bd1de9d 100644
--- a/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp
+++ b/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp
@@ -650,6 +650,7 @@ void SceneShaderForwardClustered::init(RendererStorageRD *p_storage, const Strin
 		actions.render_mode_defines["cull_front"] = "#define DO_SIDE_CHECK\n";
 		actions.render_mode_defines["cull_disabled"] = "#define DO_SIDE_CHECK\n";
 		actions.render_mode_defines["particle_trails"] = "#define USE_PARTICLE_TRAILS\n";
+		actions.render_mode_defines["depth_draw_opaque"] = "#define USE_OPAQUE_PREPASS\n";
 
 		bool force_lambert = GLOBAL_GET("rendering/shading/overrides/force_lambert_over_burley");