Shader: Fix the default behavior when mat uniforms are null

drivers/gles3/storage/material_storage.cpp

@@ -779,6 +779,13 @@ void MaterialData::update_uniform_buffer(const HashMap<StringName, ShaderLanguag
 			} else if ((E.value.type == ShaderLanguage::TYPE_VEC3 || E.value.type == ShaderLanguage::TYPE_VEC4) && E.value.hint == ShaderLanguage::ShaderNode::Uniform::HINT_COLOR_CONVERSION_DISABLED) {
 				//colors must be set as black, with alpha as 1.0
 				_fill_std140_variant_ubo_value(E.value.type, E.value.array_size, Color(0, 0, 0, 1), data);
+			} else if (E.value.type == ShaderLanguage::TYPE_MAT2) {
+				// mat uniforms are identity matrix by default.
+				_fill_std140_variant_ubo_value(E.value.type, E.value.array_size, Transform2D(), data);
+			} else if (E.value.type == ShaderLanguage::TYPE_MAT3) {
+				_fill_std140_variant_ubo_value(E.value.type, E.value.array_size, Basis(), data);
+			} else if (E.value.type == ShaderLanguage::TYPE_MAT4) {
+				_fill_std140_variant_ubo_value(E.value.type, E.value.array_size, Projection(), data);
 			} else {
 				//else just zero it out
 				_fill_std140_ubo_empty(E.value.type, E.value.array_size, data);

servers/rendering/renderer_rd/storage_rd/material_storage.cpp

@@ -812,6 +812,13 @@ void MaterialStorage::MaterialData::update_uniform_buffer(const HashMap<StringNa
 				_fill_std140_variant_ubo_value(E.value.type, E.value.array_size, Color(0, 0, 0, 1), data, p_use_linear_color);
 			} else if ((E.value.type == ShaderLanguage::TYPE_VEC3 || E.value.type == ShaderLanguage::TYPE_VEC4) && E.value.hint == ShaderLanguage::ShaderNode::Uniform::HINT_COLOR_CONVERSION_DISABLED) {
 				_fill_std140_variant_ubo_value(E.value.type, E.value.array_size, Color(0, 0, 0, 1), data, false);
+			} else if (E.value.type == ShaderLanguage::TYPE_MAT2) {
+				// mat uniforms are identity matrix by default.
+				_fill_std140_variant_ubo_value(E.value.type, E.value.array_size, Transform2D(), data, false);
+			} else if (E.value.type == ShaderLanguage::TYPE_MAT3) {
+				_fill_std140_variant_ubo_value(E.value.type, E.value.array_size, Basis(), data, false);
+			} else if (E.value.type == ShaderLanguage::TYPE_MAT4) {
+				_fill_std140_variant_ubo_value(E.value.type, E.value.array_size, Projection(), data, false);
 			} else {
 				//else just zero it out
 				_fill_std140_ubo_empty(E.value.type, E.value.array_size, data);