NODE_POSITION_WORLD and NODE_POSITION_VIEW shader built-ins do not yield the expected results ('model_matrix' : undeclared identifier)

[alfredbaudisch]

Godot version

Godot4-beta3

System information

Windows 10

Issue description

The NODE_* built-ins implemented in #63597 are currently null/0.

UPDATE: By pulling Godot from the master branch, there's now a related crash when using the NODE_* built-ins (either in a Shader and VS):

ERROR: 0:2121: 'model_matrix' : undeclared identifier 
ERROR: 0:2121: 'model_matrix' :  left of '[' is not of type array, matrix, or vector  
ERROR: 0:2121: 'assign' :  cannot convert from ' const float' to ' temp highp 3-component vector of float'
ERROR: 0:2121: '' : compilation terminated 
ERROR: 4 compilation errors.  No code generated.

To make it easy to visualize for this Issue, I set them both to the Albedo channel, so it would be possible to visualize the RGB colors changing, but no matter where in the world, there are no changes:

Expected - NODE_POSITION_WORLD / World Position

Unity:

UE:

Expected - NODE_POSITION_VIEW / Object Position

Unity:

UE:

Steps to reproduce

Use NODE_POSITION_WORLD and/or NODE_POSITION_VIEW in any shader (VS or GDShader), the result is always 0.

void fragment() {
ALBEDO = NODE_POSITION_VIEW;
}

Minimal reproduction project

NodePositionSample.zip

[clayjohn]

Cc @paddy-exe

[paddy-exe]

@clayjohn From testing I can say that there must be a regression between beta 2 and beta 3

This is how it looks like when it's working in beta 2:

_.Test.-.Godot.Engine.2022-10-26.18-05-02.mp4

[clayjohn]

@paddy-exe the issue must be from my double precision changes, I will take a look

[alekseym88]

@akien-mga @clayjohn Hello! Seems this problem is still exist, I have same problem for last godot build on MacOS Monterey, graphics: Intel Iris Graphics 550 1536 MB.

shader_type spatial;
render_mode unshaded;

void fragment() {

	vec4 view = VIEW_MATRIX * vec4(NODE_POSITION_WORLD, 1.0);
	vec3 view_n = view.xyz/view.w;
	
	if (view_n == NODE_POSITION_VIEW){
		ALBEDO = vec3(1.0, 0.0, 0.0);
	}
}

and

shader_type spatial;
render_mode unshaded;

void fragment() {

	vec4 world = INV_VIEW_MATRIX * vec4(NODE_POSITION_VIEW, 1.0);
	vec3 world_n = world.xyz/world.w;
		
	if (world_n == NODE_POSITION_WORLD){
		ALBEDO = vec3(1.0, 0.0, 0.0);
	}
}

gives a white screen instead red (as should be on IF condition)

[clayjohn]

@alekseym88 this bug report was reporting a shader compilation error that came from using those builtins. The fact that your shader compiles means you are not facing the same issue.

Your issue comes from floating point precision. By doing multiple operations, you are losing precision such that the equality operator fails. Take a look at this site for a deeper explanation about how floating point numbers work and why avoiding == between two floats is important

[Lunarexxy]

It appears that model_matrix being undeclared is still an issue in web exports. Godot 4 beta 5, tested on Firefox.

Using only this in my visual shader. (node_position_view has a similar "model_matrix undeclared" error)