Emulate double precision for regular rendering operation.

We calculate the lost precision on the CPU and pass it into the GPU
so that it can calculate an error-corrected version of the vertex position

2 files changed, 17 insertions, 2 deletions

diff --git a/servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp b/servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp
index bea31dc927..3a4c62b301 100644
--- a/servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp
+++ b/servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp
@@ -1757,6 +1757,14 @@ void RenderForwardMobile::_render_list_template(RenderingDevice::DrawListID p_dr
 			RendererRD::MaterialStorage::store_transform(Transform3D(), push_constant.transform);
 		}
 
+#ifdef REAL_T_IS_DOUBLE
+		// Split the origin into two components, the float approximation and the missing precision
+		// In the shader we will combine these back together to restore the lost precision.
+		RendererRD::MaterialStorage::split_double(inst->transform.origin.x, &push_constant.transform[12], &push_constant.transform[3]);
+		RendererRD::MaterialStorage::split_double(inst->transform.origin.y, &push_constant.transform[13], &push_constant.transform[7]);
+		RendererRD::MaterialStorage::split_double(inst->transform.origin.z, &push_constant.transform[14], &push_constant.transform[11]);
+#endif
+
 		push_constant.flags = inst->flags_cache;
 		push_constant.gi_offset = inst->gi_offset_cache;
 		push_constant.layer_mask = inst->layer_mask;
@@ -2472,6 +2480,11 @@ RenderForwardMobile::RenderForwardMobile() {
 	{
 		defines += "\n#define MATERIAL_UNIFORM_SET " + itos(MATERIAL_UNIFORM_SET) + "\n";
 	}
+#ifdef REAL_T_IS_DOUBLE
+	{
+		defines += "\n#define USE_DOUBLE_PRECISION \n";
+	}
+#endif
 
 	scene_shader.init(defines);
 
diff --git a/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp b/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp
index 383ed9247d..691d431b82 100644
--- a/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp
+++ b/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp
@@ -521,10 +521,10 @@ void SceneShaderForwardMobile::init(const String p_defines) {
 		//shader compiler
 		ShaderCompiler::DefaultIdentifierActions actions;
 
-		actions.renames["MODEL_MATRIX"] = "model_matrix";
+		actions.renames["MODEL_MATRIX"] = "read_model_matrix";
 		actions.renames["MODEL_NORMAL_MATRIX"] = "model_normal_matrix";
 		actions.renames["VIEW_MATRIX"] = "scene_data.view_matrix";
-		actions.renames["INV_VIEW_MATRIX"] = "scene_data.inv_view_matrix";
+		actions.renames["INV_VIEW_MATRIX"] = "inv_view_matrix";
 		actions.renames["PROJECTION_MATRIX"] = "projection_matrix";
 		actions.renames["INV_PROJECTION_MATRIX"] = "inv_projection_matrix";
 		actions.renames["MODELVIEW_MATRIX"] = "modelview";
@@ -657,6 +657,8 @@ void SceneShaderForwardMobile::init(const String p_defines) {
 		actions.usage_defines["RADIANCE"] = "#define CUSTOM_RADIANCE_USED\n";
 		actions.usage_defines["IRRADIANCE"] = "#define CUSTOM_IRRADIANCE_USED\n";
 
+		actions.usage_defines["MODEL_MATRIX"] = "#define MODEL_MATRIX_USED\n";
+
 		actions.render_mode_defines["skip_vertex_transform"] = "#define SKIP_TRANSFORM_USED\n";
 		actions.render_mode_defines["world_vertex_coords"] = "#define VERTEX_WORLD_COORDS_USED\n";
 		actions.render_mode_defines["ensure_correct_normals"] = "#define ENSURE_CORRECT_NORMALS\n";