Implement vertex shading

This adds support in all backends, but the Compatibility renderer works the best.
Mobile and Forward+ can only support one directional light shader (the first in the tree)
While the Compatibility renderer supports any number of shadows.

Co-authored-by: Clay John <claynjohn@gmail.com>

2 files changed, 13 insertions, 1 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 aca85ce497..307898232d 100644
--- a/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp
+++ b/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp
@@ -4261,6 +4261,11 @@ RenderForwardClustered::RenderForwardClustered() {
 		defines += "\n#define SDFGI_OCT_SIZE " + itos(gi.sdfgi_get_lightprobe_octahedron_size()) + "\n";
 		defines += "\n#define MAX_DIRECTIONAL_LIGHT_DATA_STRUCTS " + itos(MAX_DIRECTIONAL_LIGHTS) + "\n";
 
+		bool force_vertex_shading = GLOBAL_GET("rendering/shading/overrides/force_vertex_shading");
+		if (force_vertex_shading) {
+			defines += "\n#define USE_VERTEX_LIGHTING\n";
+		}
+
 		{
 			//lightmaps
 			scene_state.max_lightmaps = MAX_LIGHTMAPS;
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 6846c3f693..ee5b5ef1d8 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
@@ -730,13 +730,20 @@ void SceneShaderForwardClustered::init(const String p_defines) {
 		actions.render_mode_defines["ambient_light_disabled"] = "#define AMBIENT_LIGHT_DISABLED\n";
 		actions.render_mode_defines["shadow_to_opacity"] = "#define USE_SHADOW_TO_OPACITY\n";
 		actions.render_mode_defines["unshaded"] = "#define MODE_UNSHADED\n";
+
+		bool force_vertex_shading = GLOBAL_GET("rendering/shading/overrides/force_vertex_shading");
+		if (!force_vertex_shading) {
+			// If forcing vertex shading, this will be defined already.
+			actions.render_mode_defines["vertex_lighting"] = "#define USE_VERTEX_LIGHTING\n";
+		}
+
 		actions.render_mode_defines["debug_shadow_splits"] = "#define DEBUG_DRAW_PSSM_SPLITS\n";
 		actions.render_mode_defines["fog_disabled"] = "#define FOG_DISABLED\n";
 
 		actions.base_texture_binding_index = 1;
 		actions.texture_layout_set = RenderForwardClustered::MATERIAL_UNIFORM_SET;
 		actions.base_uniform_string = "material.";
-		actions.base_varying_index = 12;
+		actions.base_varying_index = 14;
 
 		actions.default_filter = ShaderLanguage::FILTER_LINEAR_MIPMAP;
 		actions.default_repeat = ShaderLanguage::REPEAT_ENABLE;