Uniform arrays of mat4 type are set incorrectly when an Array of Transform3D is supplied

[cdemirer]

Godot version

3b39f00

System information

Linux

Issue description

While you can set a uniform mat4 x; using a Transform3D, you can't set a uniform mat4 x[N]; using an Array of Transform3Ds (the values visible to the shader will be corrupted / incorrect). Instead, currently you have to convert the Array of Transform3Ds to a flattened PackedFloat32Array and use that as the parameter of set_shader_param.

I think the reason might be that the conversion in this line doesn't work as expected:

godot/servers/rendering/renderer_rd/storage_rd/material_storage.cpp

Line 652 in 25915cd

const PackedFloat32Array &a = value;

Somewhat related: #63064

Steps to reproduce

Given this uniform:

uniform mat4 x[1];

This doesn't work (results in bad values in shader):

my_shader_material.set_shader_param("x", [global_transform])

This works:

my_shader_material.set_shader_param("x", global_transform_as_16_floats_in_packed_array)

Minimal reproduction project

No response

[clayjohn]

Implementation here:

godot/servers/rendering/renderer_rd/storage_rd/material_storage.cpp

Lines 651 to 655 in 40b9c24

	if (p_array_size > 0) {
	const PackedFloat32Array &a = value;
	int s = a.size();
	for (int i = 0; i < p_array_size * 16; i += 16) {

the conditional checks whether an array is passed, if so, it reads the data like an array of floats, otherwise, if the variant is a transform, it will read the transform directly. I guess we need another conditional within the array branch to see if the array contains Transform3Ds, or we need to at least to error in the case that an array other than a PackedFloat32Array is used

[faylite]

I've encountered the same issue with arrays of mat3 and Basis. But I see @bitsawer is already ahead of the curve here 🥇